test: remove thread-safe wrapper

2026-07-26 22:58:41 +00:00 · 2021-04-06 21:46:13 +09:00
248 changed files with 2586 additions and 7189 deletions
@@ -68,17 +68,14 @@ commands:
    steps:
      - restore_cache:
          keys:
-            - llvm-source-11-v2
+            - llvm-source-11-v1
      - run:
          name: "Fetch LLVM source"
          command: make llvm-source
      - save_cache:
-          key: llvm-source-11-v2
+          key: llvm-source-11-v1
          paths:
-            - llvm-project/clang/lib/Headers
-            - llvm-project/clang/include
-            - llvm-project/lld/include
-            - llvm-project/llvm/include
+            - llvm-project
  build-wasi-libc:
    steps:
      - restore_cache:
@@ -157,15 +154,12 @@ commands:
      - llvm-source-linux
      - restore_cache:
          keys:
-            - llvm-build-11-linux-v3-assert
+            - llvm-build-11-linux-v2-assert
      - run:
          name: "Build LLVM"
          command: |
            if [ ! -f llvm-build/lib/liblldELF.a ]
            then
-              # fetch LLVM source
-              rm -rf llvm-project
-              make llvm-source
              # install dependencies
              sudo apt-get install cmake ninja-build
              # hack ninja to use less jobs
@@ -173,22 +167,20 @@ commands:
              chmod +x /go/bin/ninja
              # build!
              make ASSERT=1 llvm-build
-              find llvm-build -name CMakeFiles -prune -exec rm -r '{}' \;
            fi
      - save_cache:
-          key: llvm-build-11-linux-v3-assert
+          key: llvm-build-11-linux-v2-assert
          paths:
            llvm-build
-      - run: make ASSERT=1
+      - run: |
+          # Note: -p=2 limits parallelism to two jobs at a time, which is
+          # necessary to keep memory consumption down and avoid OOM (for a
+          # 2CPU/4GB executor).
+          GOFLAGS="-p=2" make ASSERT=1
      - build-wasi-libc
      - run:
          name: "Test TinyGo"
          command: make ASSERT=1 test
-          environment:
-            # Note: -p=2 limits parallelism to two jobs at a time, which is
-            # necessary to keep memory consumption down and avoid OOM (for a
-            # 2CPU/4GB executor).
-            GOFLAGS: -p=2
      - save_cache:
          key: go-cache-v2-{{ checksum "go.mod" }}-{{ .Environment.CIRCLE_BUILD_NUM }}
          paths:
@@ -225,15 +217,12 @@ commands:
      - llvm-source-linux
      - restore_cache:
          keys:
-            - llvm-build-11-linux-v3-noassert
+            - llvm-build-11-linux-v2-noassert
      - run:
          name: "Build LLVM"
          command: |
            if [ ! -f llvm-build/lib/liblldELF.a ]
            then
-              # fetch LLVM source
-              rm -rf llvm-project
-              make llvm-source
              # install dependencies
              sudo apt-get install cmake ninja-build
              # hack ninja to use less jobs
@@ -241,10 +230,9 @@ commands:
              chmod +x /go/bin/ninja
              # build!
              make llvm-build
-              find llvm-build -name CMakeFiles -prune -exec rm -r '{}' \;
            fi
      - save_cache:
-          key: llvm-build-11-linux-v3-noassert
+          key: llvm-build-11-linux-v2-noassert
          paths:
            llvm-build
      - build-wasi-libc
@@ -294,50 +282,43 @@ commands:
          variant: "macos"
      - restore_cache:
          keys:
-            - go-cache-macos-v3-{{ checksum "go.mod" }}-{{ .Environment.CIRCLE_PREVIOUS_BUILD_NUM }}
-            - go-cache-macos-v3-{{ checksum "go.mod" }}
+            - go-cache-macos-v2-{{ checksum "go.mod" }}-{{ .Environment.CIRCLE_PREVIOUS_BUILD_NUM }}
+            - go-cache-macos-v2-{{ checksum "go.mod" }}
      - restore_cache:
          keys:
-            - llvm-source-11-macos-v3
+            - llvm-source-11-macos-v1
      - run:
          name: "Fetch LLVM source"
          command: make llvm-source
      - save_cache:
-          key: llvm-source-11-macos-v3
+          key: llvm-source-11-macos-v1
          paths:
-            - llvm-project/clang/lib/Headers
-            - llvm-project/clang/include
-            - llvm-project/lld/include
-            - llvm-project/llvm/include
+            - llvm-project
      - restore_cache:
          keys:
-            - llvm-build-11-macos-v4
+            - llvm-build-11-macos-v2
      - run:
          name: "Build LLVM"
          command: |
            if [ ! -f llvm-build/lib/liblldELF.a ]
            then
-              # fetch LLVM source
-              rm -rf llvm-project
-              make llvm-source
              # install dependencies
              HOMEBREW_NO_AUTO_UPDATE=1 brew install cmake ninja
              # build!
              make llvm-build
-              find llvm-build -name CMakeFiles -prune -exec rm -r '{}' \;
            fi
      - save_cache:
-          key: llvm-build-11-macos-v4
+          key: llvm-build-11-macos-v2
          paths:
            llvm-build
      - restore_cache:
          keys:
-            - wasi-libc-sysroot-macos-v4
+            - wasi-libc-sysroot-macos-v3
      - run:
          name: "Build wasi-libc"
          command: make wasi-libc
      - save_cache:
-          key: wasi-libc-sysroot-macos-v4
+          key: wasi-libc-sysroot-macos-v3
          paths:
            - lib/wasi-libc/sysroot
      - run:
@@ -359,7 +340,7 @@ commands:
            tinygo version
      - run: make smoketest AVR=0
      - save_cache:
-          key: go-cache-macos-v3-{{ checksum "go.mod" }}-{{ .Environment.CIRCLE_BUILD_NUM }}
+          key: go-cache-macos-v2-{{ checksum "go.mod" }}-{{ .Environment.CIRCLE_BUILD_NUM }}
          paths:
            - ~/.cache/go-build
            - /go/pkg/mod
@@ -401,7 +382,7 @@ jobs:
      - build-linux
  build-macos:
    macos:
-      xcode: "11.1.0" # macOS 10.14
+      xcode: "10.1.0"
    steps:
      - build-macos

@@ -152,9 +152,9 @@ gen-device-stm32: build/gen-device-svd


 # Get LLVM sources.
-$(LLVM_PROJECTDIR)/llvm:
+$(LLVM_PROJECTDIR)/README.md:
 	git clone -b xtensa_release_11.0.0 --depth=1 https://github.com/tinygo-org/llvm-project $(LLVM_PROJECTDIR)
-llvm-source: $(LLVM_PROJECTDIR)/llvm
+llvm-source: $(LLVM_PROJECTDIR)/README.md

 # Configure LLVM.
 TINYGO_SOURCE_DIR=$(shell pwd)
@@ -182,28 +182,25 @@ tinygo:
 test: wasi-libc
 	CGO_CPPFLAGS="$(CGO_CPPFLAGS)" CGO_CXXFLAGS="$(CGO_CXXFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" $(GO) test -v -buildmode exe -tags byollvm ./builder ./cgo ./compileopts ./compiler ./interp ./transform .

-TEST_PACKAGES = \
-	container/heap \
-	container/list \
-	container/ring \
-	crypto/des \
-	encoding \
-	encoding/ascii85 \
-	encoding/base32 \
-	encoding/hex \
-	hash/adler32 \
-	hash/fnv \
-	hash/crc64 \
-	math \
-	math/cmplx \
-	text/scanner \
-	unicode/utf8 \
-
 # Test known-working standard library packages.
-# TODO: parallelize, and only show failing tests (no implied -v flag).
+# TODO: do this in one command, parallelize, and only show failing tests (no
+# implied -v flag).
 .PHONY: tinygo-test
 tinygo-test:
-	$(TINYGO) test $(TEST_PACKAGES)
+	$(TINYGO) test container/heap
+	$(TINYGO) test container/list
+	$(TINYGO) test container/ring
+	$(TINYGO) test crypto/des
+	$(TINYGO) test encoding/ascii85
+	$(TINYGO) test encoding/base32
+	$(TINYGO) test encoding/hex
+	$(TINYGO) test hash/adler32
+	$(TINYGO) test hash/fnv
+	$(TINYGO) test hash/crc64
+	$(TINYGO) test math
+	$(TINYGO) test math/cmplx
+	$(TINYGO) test text/scanner
+	$(TINYGO) test unicode/utf8

 .PHONY: smoketest
 smoketest:
@@ -229,6 +226,8 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=microbit            examples/microbit-blink
 	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=microbit-v2         examples/microbit-blink
+	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10040            examples/pininterrupt
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10040            examples/serial
@@ -257,10 +256,6 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=microbit-s110v8     examples/echo
 	@$(MD5SUM) test.hex
-	$(TINYGO) build -size short -o test.hex -target=microbit-v2         examples/microbit-blink
-	@$(MD5SUM) test.hex
-	$(TINYGO) build -size short -o test.hex -target=microbit-v2-s113v7  examples/microbit-blink
-	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=nrf52840-mdk        examples/blinky1
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10031            examples/blinky1
@@ -293,8 +288,6 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.gba -target=gameboy-advance     examples/gba-display
 	@$(MD5SUM) test.gba
-	$(TINYGO) build -size short -o test.hex -target=grandcentral-m4     examples/blinky1
-	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=itsybitsy-m4        examples/blinky1
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=feather-m4          examples/blinky1
@@ -341,10 +334,6 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=p1am-100            examples/blinky1
 	@$(MD5SUM) test.hex
-	$(TINYGO) build -size short -o test.hex -target=atsame54-xpro       examples/blinky1
-	@$(MD5SUM) test.hex
-	$(TINYGO) build -size short -o test.hex -target=feather-m4-can      examples/blinky1
-	@$(MD5SUM) test.hex
 	# test pwm
 	$(TINYGO) build -size short -o test.hex -target=itsybitsy-m0        examples/pwm
 	@$(MD5SUM) test.hex
@@ -352,6 +341,8 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=feather-m4          examples/pwm
 	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=pyportal            examples/pwm
+	@$(MD5SUM) test.hex
 ifneq ($(STM32), 0)
 	$(TINYGO) build -size short -o test.hex -target=bluepill            examples/blinky1
 	@$(MD5SUM) test.hex
@@ -363,8 +354,6 @@ ifneq ($(STM32), 0)
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=nucleo-f722ze       examples/blinky1
 	@$(MD5SUM) test.hex
-	$(TINYGO) build -size short -o test.hex -target=nucleo-l031k6       examples/blinky1
-	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=nucleo-l432kc       examples/blinky1
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=nucleo-l552ze       examples/blinky1
@@ -385,10 +374,6 @@ ifneq ($(AVR), 0)
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=arduino -scheduler=tasks  examples/blinky1
 	@$(MD5SUM) test.hex
-	$(TINYGO) build -size short -o test.hex -target=arduino-mega1280    examples/blinky1
-	@$(MD5SUM) test.hex
-	$(TINYGO) build -size short -o test.hex -target=arduino-mega1280    examples/pwm
-	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=arduino-nano        examples/blinky1
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=digispark           examples/blinky1
@@ -43,14 +43,13 @@ See the [getting started instructions](https://tinygo.org/getting-started/) for

 You can compile TinyGo programs for microcontrollers, WebAssembly and Linux.

-The following 57 microcontroller boards are currently supported:
+The following 55 microcontroller boards are currently supported:

 * [Adafruit Circuit Playground Bluefruit](https://www.adafruit.com/product/4333)
 * [Adafruit Circuit Playground Express](https://www.adafruit.com/product/3333)
 * [Adafruit CLUE](https://www.adafruit.com/product/4500)
 * [Adafruit Feather M0](https://www.adafruit.com/product/2772)
 * [Adafruit Feather M4](https://www.adafruit.com/product/3857)
-* [Adafruit Feather M4 CAN](https://www.adafruit.com/product/4759)
 * [Adafruit Feather nRF52840 Express](https://www.adafruit.com/product/4062)
 * [Adafruit Feather STM32F405 Express](https://www.adafruit.com/product/4382)
 * [Adafruit ItsyBitsy M0](https://www.adafruit.com/product/3727)
@@ -78,7 +77,6 @@ The following 57 microcontroller boards are currently supported:
 * [Game Boy Advance](https://en.wikipedia.org/wiki/Game_Boy_Advance)
 * [Makerdiary nRF52840-MDK](https://wiki.makerdiary.com/nrf52840-mdk/)
 * [Makerdiary nRF52840-MDK USB Dongle](https://wiki.makerdiary.com/nrf52840-mdk-usb-dongle/)
-* [Microchip SAM E54 Xplained Pro](https://www.microchip.com/developmenttools/productdetails/atsame54-xpro)
 * [nice!nano](https://docs.nicekeyboards.com/#/nice!nano/)
 * [Nintendo Switch](https://www.nintendo.com/switch/)
 * [Nordic Semiconductor PCA10031](https://www.nordicsemi.com/eng/Products/nRF51-Dongle)
@@ -39,11 +39,6 @@ type BuildResult struct {
 	// The directory of the main package. This is useful for testing as the test
 	// binary must be run in the directory of the tested package.
 	MainDir string
-
-	// ImportPath is the import path of the main package. This is useful for
-	// correctly printing test results: the import path isn't always the same as
-	// the path listed on the command line.
-	ImportPath string
 }

 // packageAction is the struct that is serialized to JSON and hashed, to work as
@@ -57,17 +52,14 @@ type BuildResult struct {
 // key, avoiding the need for recompiling all dependencies when only the
 // implementation of an imported package changes.
 type packageAction struct {
-	ImportPath       string
-	CompilerVersion  int // compiler.Version
-	InterpVersion    int // interp.Version
-	LLVMVersion      string
-	Config           *compiler.Config
-	CFlags           []string
-	FileHashes       map[string]string // hash of every file that's part of the package
-	Imports          map[string]string // map from imported package to action ID hash
-	OptLevel         int               // LLVM optimization level (0-3)
-	SizeLevel        int               // LLVM optimization for size level (0-2)
-	UndefinedGlobals []string          // globals that are left as external globals (no initializer)
+	ImportPath      string
+	CompilerVersion int // compiler.Version
+	InterpVersion   int // interp.Version
+	LLVMVersion     string
+	Config          *compiler.Config
+	CFlags          []string
+	FileHashes      map[string]string // hash of every file that's part of the package
+	Imports         map[string]string // map from imported package to action ID hash
 }

 // Build performs a single package to executable Go build. It takes in a package
@@ -99,7 +91,6 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 		DefaultStackSize:   config.Target.DefaultStackSize,
 		NeedsStackObjects:  config.NeedsStackObjects(),
 		Debug:              config.Debug(),
-		LLVMFeatures:       config.LLVMFeatures(),
 	}

 	// Load the target machine, which is the LLVM object that contains all
@@ -136,30 +127,20 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 	var packageJobs []*compileJob
 	packageBitcodePaths := make(map[string]string)
 	packageActionIDs := make(map[string]string)
-	optLevel, sizeLevel, _ := config.OptLevels()
 	for _, pkg := range lprogram.Sorted() {
 		pkg := pkg // necessary to avoid a race condition

-		var undefinedGlobals []string
-		for name := range config.Options.GlobalValues[pkg.Pkg.Path()] {
-			undefinedGlobals = append(undefinedGlobals, name)
-		}
-		sort.Strings(undefinedGlobals)
-
 		// Create a cache key: a hash from the action ID below that contains all
 		// the parameters for the build.
 		actionID := packageAction{
-			ImportPath:       pkg.ImportPath,
-			CompilerVersion:  compiler.Version,
-			InterpVersion:    interp.Version,
-			LLVMVersion:      llvm.Version,
-			Config:           compilerConfig,
-			CFlags:           pkg.CFlags,
-			FileHashes:       make(map[string]string, len(pkg.FileHashes)),
-			Imports:          make(map[string]string, len(pkg.Pkg.Imports())),
-			OptLevel:         optLevel,
-			SizeLevel:        sizeLevel,
-			UndefinedGlobals: undefinedGlobals,
+			ImportPath:      pkg.ImportPath,
+			CompilerVersion: compiler.Version,
+			InterpVersion:   interp.Version,
+			LLVMVersion:     llvm.Version,
+			Config:          compilerConfig,
+			CFlags:          pkg.CFlags,
+			FileHashes:      make(map[string]string, len(pkg.FileHashes)),
+			Imports:         make(map[string]string, len(pkg.Pkg.Imports())),
 		}
 		for filePath, hash := range pkg.FileHashes {
 			actionID.FileHashes[filePath] = hex.EncodeToString(hash)
@@ -210,25 +191,6 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 					return errors.New("verification error after compiling package " + pkg.ImportPath)
 				}

-				// Erase all globals that are part of the undefinedGlobals list.
-				// This list comes from the -ldflags="-X pkg.foo=val" option.
-				// Instead of setting the value directly in the AST (which would
-				// mean the value, which may be a secret, is stored in the build
-				// cache), the global itself is left external (undefined) and is
-				// only set at the end of the compilation.
-				for _, name := range undefinedGlobals {
-					globalName := pkg.Pkg.Path() + "." + name
-					global := mod.NamedGlobal(globalName)
-					if global.IsNil() {
-						return errors.New("global not found: " + globalName)
-					}
-					name := global.Name()
-					newGlobal := llvm.AddGlobal(mod, global.Type().ElementType(), name+".tmp")
-					global.ReplaceAllUsesWith(newGlobal)
-					global.EraseFromParentAsGlobal()
-					newGlobal.SetName(name)
-				}
-
 				// Try to interpret package initializers at compile time.
 				// It may only be possible to do this partially, in which case
 				// it is completed after all IR files are linked.
@@ -244,38 +206,6 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 					return errors.New("verification error after interpreting " + pkgInit.Name())
 				}

-				if sizeLevel >= 2 {
-					// Set the "optsize" attribute to make slightly smaller
-					// binaries at the cost of some performance.
-					kind := llvm.AttributeKindID("optsize")
-					attr := mod.Context().CreateEnumAttribute(kind, 0)
-					for fn := mod.FirstFunction(); !fn.IsNil(); fn = llvm.NextFunction(fn) {
-						fn.AddFunctionAttr(attr)
-					}
-				}
-
-				// Run function passes for each function in the module.
-				// These passes are intended to be run on each function right
-				// after they're created to reduce IR size (and maybe also for
-				// cache locality to improve performance), but for now they're
-				// run here for each function in turn. Maybe this can be
-				// improved in the future.
-				builder := llvm.NewPassManagerBuilder()
-				defer builder.Dispose()
-				builder.SetOptLevel(optLevel)
-				builder.SetSizeLevel(sizeLevel)
-				funcPasses := llvm.NewFunctionPassManagerForModule(mod)
-				defer funcPasses.Dispose()
-				builder.PopulateFunc(funcPasses)
-				funcPasses.InitializeFunc()
-				for fn := mod.FirstFunction(); !fn.IsNil(); fn = llvm.NextFunction(fn) {
-					if fn.IsDeclaration() {
-						continue
-					}
-					funcPasses.RunFunc(fn)
-				}
-				funcPasses.FinalizeFunc()
-
 				// Serialize the LLVM module as a bitcode file.
 				// Write to a temporary path that is renamed to the destination
 				// file to avoid race conditions with other TinyGo invocatiosn
@@ -500,7 +430,7 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 		job := &compileJob{
 			description: "compile extra file " + path,
 			run: func(job *compileJob) error {
-				result, err := compileAndCacheCFile(abspath, dir, config.CFlags(), config.Options.PrintCommands)
+				result, err := compileAndCacheCFile(abspath, dir, config.CFlags(), config)
 				job.result = result
 				return err
 			},
@@ -519,7 +449,7 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 			job := &compileJob{
 				description: "compile CGo file " + abspath,
 				run: func(job *compileJob) error {
-					result, err := compileAndCacheCFile(abspath, dir, pkg.CFlags, config.Options.PrintCommands)
+					result, err := compileAndCacheCFile(abspath, dir, pkg.CFlags, config)
 					job.result = result
 					return err
 				},
@@ -643,9 +573,8 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 		return fmt.Errorf("unknown output binary format: %s", outputBinaryFormat)
 	}
 	return action(BuildResult{
-		Binary:     tmppath,
-		MainDir:    lprogram.MainPkg().Dir,
-		ImportPath: lprogram.MainPkg().ImportPath,
+		Binary:  tmppath,
+		MainDir: lprogram.MainPkg().Dir,
 	})
 }

@@ -674,12 +603,6 @@ func optimizeProgram(mod llvm.Module, config *compileopts.Config) error {
 		transform.ApplyFunctionSections(mod) // -ffunction-sections
 	}

-	// Insert values from -ldflags="-X ..." into the IR.
-	err = setGlobalValues(mod, config.Options.GlobalValues)
-	if err != nil {
-		return err
-	}
-
 	// Browsers cannot handle external functions that have type i64 because it
 	// cannot be represented exactly in JavaScript (JS only has doubles). To
 	// keep functions interoperable, pass int64 types as pointers to
@@ -694,8 +617,21 @@ func optimizeProgram(mod llvm.Module, config *compileopts.Config) error {

 	// Optimization levels here are roughly the same as Clang, but probably not
 	// exactly.
-	optLevel, sizeLevel, inlinerThreshold := config.OptLevels()
-	errs := transform.Optimize(mod, config, optLevel, sizeLevel, inlinerThreshold)
+	var errs []error
+	switch config.Options.Opt {
+	case "none", "0":
+		errs = transform.Optimize(mod, config, 0, 0, 0) // -O0
+	case "1":
+		errs = transform.Optimize(mod, config, 1, 0, 0) // -O1
+	case "2":
+		errs = transform.Optimize(mod, config, 2, 0, 225) // -O2
+	case "s":
+		errs = transform.Optimize(mod, config, 2, 1, 225) // -Os
+	case "z":
+		errs = transform.Optimize(mod, config, 2, 2, 5) // -Oz, default
+	default:
+		return errors.New("unknown optimization level: -opt=" + config.Options.Opt)
+	}
 	if len(errs) > 0 {
 		return newMultiError(errs)
 	}
@@ -717,71 +653,6 @@ func optimizeProgram(mod llvm.Module, config *compileopts.Config) error {
 	return nil
 }

-// setGlobalValues sets the global values from the -ldflags="-X ..." compiler
-// option in the given module. An error may be returned if the global is not of
-// the expected type.
-func setGlobalValues(mod llvm.Module, globals map[string]map[string]string) error {
-	var pkgPaths []string
-	for pkgPath := range globals {
-		pkgPaths = append(pkgPaths, pkgPath)
-	}
-	sort.Strings(pkgPaths)
-	for _, pkgPath := range pkgPaths {
-		pkg := globals[pkgPath]
-		var names []string
-		for name := range pkg {
-			names = append(names, name)
-		}
-		sort.Strings(names)
-		for _, name := range names {
-			value := pkg[name]
-			globalName := pkgPath + "." + name
-			global := mod.NamedGlobal(globalName)
-			if global.IsNil() || !global.Initializer().IsNil() {
-				// The global either does not exist (optimized away?) or has
-				// some value, in which case it has already been initialized at
-				// package init time.
-				continue
-			}
-
-			// A strin is a {ptr, len} pair. We need these types to build the
-			// initializer.
-			initializerType := global.Type().ElementType()
-			if initializerType.TypeKind() != llvm.StructTypeKind || initializerType.StructName() == "" {
-				return fmt.Errorf("%s: not a string", globalName)
-			}
-			elementTypes := initializerType.StructElementTypes()
-			if len(elementTypes) != 2 {
-				return fmt.Errorf("%s: not a string", globalName)
-			}
-
-			// Create a buffer for the string contents.
-			bufInitializer := mod.Context().ConstString(value, false)
-			buf := llvm.AddGlobal(mod, bufInitializer.Type(), ".string")
-			buf.SetInitializer(bufInitializer)
-			buf.SetAlignment(1)
-			buf.SetUnnamedAddr(true)
-			buf.SetLinkage(llvm.PrivateLinkage)
-
-			// Create the string value, which is a {ptr, len} pair.
-			zero := llvm.ConstInt(mod.Context().Int32Type(), 0, false)
-			ptr := llvm.ConstGEP(buf, []llvm.Value{zero, zero})
-			if ptr.Type() != elementTypes[0] {
-				return fmt.Errorf("%s: not a string", globalName)
-			}
-			length := llvm.ConstInt(elementTypes[1], uint64(len(value)), false)
-			initializer := llvm.ConstNamedStruct(initializerType, []llvm.Value{
-				ptr,
-				length,
-			})
-
-			// Set the initializer. No initializer should be set at this point.
-			global.SetInitializer(initializer)
-		}
-	}
-	return nil
-}
-
 // functionStackSizes keeps stack size information about a single function
 // (usually a goroutine).
 type functionStackSize struct {
@@ -17,6 +17,7 @@ import (
 	"strings"
 	"unicode"

+	"github.com/tinygo-org/tinygo/compileopts"
 	"github.com/tinygo-org/tinygo/goenv"
 	"tinygo.org/x/go-llvm"
 )
@@ -56,7 +57,7 @@ import (
 //   depfile but without invalidating its name. For this reason, the depfile is
 //   written on each new compilation (even when it seems unnecessary). However, it
 //   could in rare cases lead to a stale file fetched from the cache.
-func compileAndCacheCFile(abspath, tmpdir string, cflags []string, printCommands bool) (string, error) {
+func compileAndCacheCFile(abspath, tmpdir string, cflags []string, config *compileopts.Config) (string, error) {
 	// Hash input file.
 	fileHash, err := hashFile(abspath)
 	if err != nil {
@@ -67,12 +68,14 @@ func compileAndCacheCFile(abspath, tmpdir string, cflags []string, printCommands
 	buf, err := json.Marshal(struct {
 		Path        string
 		Hash        string
+		Compiler    string
 		Flags       []string
 		LLVMVersion string
 	}{
 		Path:        abspath,
 		Hash:        fileHash,
-		Flags:       cflags,
+		Compiler:    config.Target.Compiler,
+		Flags:       config.CFlags(),
 		LLVMVersion: llvm.Version,
 	})
 	if err != nil {
@@ -121,17 +124,10 @@ func compileAndCacheCFile(abspath, tmpdir string, cflags []string, printCommands
 	flags := append([]string{}, cflags...)                                   // copy cflags
 	flags = append(flags, "-MD", "-MV", "-MTdeps", "-MF", depTmpFile.Name()) // autogenerate dependencies
 	flags = append(flags, "-c", "-o", objTmpFile.Name(), abspath)
-	if strings.ToLower(filepath.Ext(abspath)) == ".s" {
-		// If this is an assembly file (.s or .S, lowercase or uppercase), then
-		// we'll need to add -Qunused-arguments because many parameters are
-		// relevant to C, not assembly. And with -Werror, having meaningless
-		// flags (for the assembler) is a compiler error.
-		flags = append(flags, "-Qunused-arguments")
+	if config.Options.PrintCommands {
+		fmt.Printf("%s %s\n", config.Target.Compiler, strings.Join(flags, " "))
 	}
-	if printCommands {
-		fmt.Printf("clang %s\n", strings.Join(flags, " "))
-	}
-	err = runCCompiler(flags...)
+	err = runCCompiler(config.Target.Compiler, flags...)
 	if err != nil {
 		return "", &commandError{"failed to build", abspath, err}
 	}
@@ -17,18 +17,10 @@ func NewConfig(options *compileopts.Options) (*compileopts.Config, error) {
 	if err != nil {
 		return nil, err
 	}
-
-	if options.OpenOCDCommands != nil {
-		// Override the OpenOCDCommands from the target spec if specified on
-		// the command-line
-		spec.OpenOCDCommands = options.OpenOCDCommands
-	}
-
 	goroot := goenv.Get("GOROOT")
 	if goroot == "" {
 		return nil, errors.New("cannot locate $GOROOT, please set it manually")
 	}
-
 	major, minor, err := goenv.GetGorootVersion(goroot)
 	if err != nil {
 		return nil, fmt.Errorf("could not read version from GOROOT (%v): %v", goroot, err)
@@ -36,9 +28,7 @@ func NewConfig(options *compileopts.Options) (*compileopts.Config, error) {
 	if major != 1 || minor < 13 || minor > 16 {
 		return nil, fmt.Errorf("requires go version 1.13 through 1.16, got go%d.%d", major, minor)
 	}
-
 	clangHeaderPath := getClangHeaderPath(goenv.Get("TINYGOROOT"))
-
 	return &compileopts.Config{
 		Options:        options,
 		Target:         spec,
@@ -136,7 +136,7 @@ func (l *Library) load(target, cpu, tmpdir string) (job *compileJob, err error)
 				var compileArgs []string
 				compileArgs = append(compileArgs, args...)
 				compileArgs = append(compileArgs, "-o", objpath, srcpath)
-				err := runCCompiler(compileArgs...)
+				err := runCCompiler("clang", compileArgs...)
 				if err != nil {
 					return &commandError{"failed to build", srcpath, err}
 				}
@@ -9,8 +9,8 @@ import (
 )

 // runCCompiler invokes a C compiler with the given arguments.
-func runCCompiler(flags ...string) error {
-	if hasBuiltinTools {
+func runCCompiler(command string, flags ...string) error {
+	if hasBuiltinTools && command == "clang" {
 		// Compile this with the internal Clang compiler.
 		headerPath := getClangHeaderPath(goenv.Get("TINYGOROOT"))
 		if headerPath == "" {
@@ -23,8 +23,17 @@ func runCCompiler(flags ...string) error {
 		return cmd.Run()
 	}

-	// Compile this with an external invocation of the Clang compiler.
-	return execCommand(commands["clang"], flags...)
+	// Running some other compiler. Maybe it has been defined in the
+	// commands map (unlikely).
+	if cmdNames, ok := commands[command]; ok {
+		return execCommand(cmdNames, flags...)
+	}
+
+	// Alternatively, run the compiler directly.
+	cmd := exec.Command(command, flags...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
 }

 // link invokes a linker with the given name and flags.
@@ -80,7 +80,12 @@ func (c *Config) GC() string {
 	if c.Target.GC != "" {
 		return c.Target.GC
 	}
-	return "conservative"
+	for _, tag := range c.Target.BuildTags {
+		if tag == "baremetal" || tag == "wasm" {
+			return "conservative"
+		}
+	}
+	return "extalloc"
 }

 // NeedsStackObjects returns true if the compiler should insert stack objects
@@ -113,27 +118,6 @@ func (c *Config) Scheduler() string {
 	return "coroutines"
 }

-// OptLevels returns the optimization level (0-2), size level (0-2), and inliner
-// threshold as used in the LLVM optimization pipeline.
-func (c *Config) OptLevels() (optLevel, sizeLevel int, inlinerThreshold uint) {
-	switch c.Options.Opt {
-	case "none", "0":
-		return 0, 0, 0 // -O0
-	case "1":
-		return 1, 0, 0 // -O1
-	case "2":
-		return 2, 0, 225 // -O2
-	case "s":
-		return 2, 1, 225 // -Os
-	case "z":
-		return 2, 2, 5 // -Oz, default
-	default:
-		// This is not shown to the user: valid choices are already checked as
-		// part of Options.Verify(). It is here as a sanity check.
-		panic("unknown optimization level: -opt=" + c.Options.Opt)
-	}
-}
-
 // FuncImplementation picks an appropriate func value implementation for the
 // target.
 func (c *Config) FuncImplementation() string {
@@ -179,7 +163,7 @@ func (c *Config) AutomaticStackSize() bool {
 // CFlags returns the flags to pass to the C compiler. This is necessary for CGo
 // preprocessing.
 func (c *Config) CFlags() []string {
-	var cflags []string
+	cflags := append([]string{}, c.Options.CFlags...)
 	for _, flag := range c.Target.CFlags {
 		cflags = append(cflags, strings.ReplaceAll(flag, "{root}", goenv.Get("TINYGOROOT")))
 	}
@@ -200,7 +184,7 @@ func (c *Config) CFlags() []string {
 func (c *Config) LDFlags() []string {
 	root := goenv.Get("TINYGOROOT")
 	// Merge and adjust LDFlags.
-	var ldflags []string
+	ldflags := append([]string{}, c.Options.LDFlags...)
 	for _, flag := range c.Target.LDFlags {
 		ldflags = append(ldflags, strings.ReplaceAll(flag, "{root}", root))
 	}
@@ -337,10 +321,6 @@ func (c *Config) WasmAbi() string {
 	return c.Target.WasmAbi
 }

-func (c *Config) LLVMFeatures() string {
-	return c.Options.LLVMFeatures
-}
-
 type TestConfig struct {
 	CompileTestBinary bool
 	// TODO: Filter the test functions to run, include verbose flag, etc
@@ -2,7 +2,6 @@ package compileopts

 import (
 	"fmt"
-	"regexp"
 	"strings"
 )

@@ -11,32 +10,29 @@ var (
 	validSchedulerOptions     = []string{"none", "tasks", "coroutines"}
 	validPrintSizeOptions     = []string{"none", "short", "full"}
 	validPanicStrategyOptions = []string{"print", "trap"}
-	validOptOptions           = []string{"none", "0", "1", "2", "s", "z"}
 )

 // Options contains extra options to give to the compiler. These options are
 // usually passed from the command line.
 type Options struct {
-	Target          string
-	Opt             string
-	GC              string
-	PanicStrategy   string
-	Scheduler       string
-	PrintIR         bool
-	DumpSSA         bool
-	VerifyIR        bool
-	PrintCommands   bool
-	Debug           bool
-	PrintSizes      string
-	PrintAllocs     *regexp.Regexp // regexp string
-	PrintStacks     bool
-	Tags            string
-	WasmAbi         string
-	GlobalValues    map[string]map[string]string // map[pkgpath]map[varname]value
-	TestConfig      TestConfig
-	Programmer      string
-	OpenOCDCommands []string
-	LLVMFeatures    string
+	Target        string
+	Opt           string
+	GC            string
+	PanicStrategy string
+	Scheduler     string
+	PrintIR       bool
+	DumpSSA       bool
+	VerifyIR      bool
+	PrintCommands bool
+	Debug         bool
+	PrintSizes    string
+	PrintStacks   bool
+	CFlags        []string
+	LDFlags       []string
+	Tags          string
+	WasmAbi       string
+	TestConfig    TestConfig
+	Programmer    string
 }

 // Verify performs a validation on the given options, raising an error if options are not valid.
@@ -77,12 +73,6 @@ func (o *Options) Verify() error {
 		}
 	}

-	if o.Opt != "" {
-		if !isInArray(validOptOptions, o.Opt) {
-			return fmt.Errorf("invalid -opt=%s: valid values are %s", o.Opt, strings.Join(validOptOptions, ", "))
-		}
-	}
-
 	return nil
 }

@@ -31,6 +31,7 @@ type TargetSpec struct {
 	BuildTags        []string `json:"build-tags"`
 	GC               string   `json:"gc"`
 	Scheduler        string   `json:"scheduler"`
+	Compiler         string   `json:"compiler"`
 	Linker           string   `json:"linker"`
 	RTLib            string   `json:"rtlib"` // compiler runtime library (libgcc, compiler-rt)
 	Libc             string   `json:"libc"`
@@ -239,26 +240,23 @@ func defaultTarget(goos, goarch, triple string) (*TargetSpec, error) {
 	// No target spec available. Use the default one, useful on most systems
 	// with a regular OS.
 	spec := TargetSpec{
-		Triple:           triple,
-		GOOS:             goos,
-		GOARCH:           goarch,
-		BuildTags:        []string{goos, goarch},
-		Scheduler:        "tasks",
-		Linker:           "cc",
-		DefaultStackSize: 1024 * 64, // 64kB
-		CFlags:           []string{"--target=" + triple},
-		GDB:              []string{"gdb"},
-		PortReset:        "false",
+		Triple:    triple,
+		GOOS:      goos,
+		GOARCH:    goarch,
+		BuildTags: []string{goos, goarch},
+		Compiler:  "clang",
+		Linker:    "cc",
+		CFlags:    []string{"--target=" + triple},
+		GDB:       []string{"gdb"},
+		PortReset: "false",
 	}
 	if goos == "darwin" {
-		spec.CFlags = append(spec.CFlags, "-isysroot", "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk")
 		spec.LDFlags = append(spec.LDFlags, "-Wl,-dead_strip")
 	} else {
 		spec.LDFlags = append(spec.LDFlags, "-no-pie", "-Wl,--gc-sections") // WARNING: clang < 5.0 requires -nopie
 	}
 	if goarch != "wasm" {
 		spec.ExtraFiles = append(spec.ExtraFiles, "src/runtime/gc_"+goarch+".S")
-		spec.ExtraFiles = append(spec.ExtraFiles, "src/internal/task/task_stack_"+goarch+".S")
 	}
 	if goarch != runtime.GOARCH {
 		// Some educated guesses as to how to invoke helper programs.
@@ -23,7 +23,7 @@ import (
 // Version of the compiler pacakge. Must be incremented each time the compiler
 // package changes in a way that affects the generated LLVM module.
 // This version is independent of the TinyGo version number.
-const Version = 9 // last change: implement reflect.New()
+const Version = 6 // last change: fix issue 1304

 func init() {
 	llvm.InitializeAllTargets()
@@ -59,7 +59,6 @@ type Config struct {
 	DefaultStackSize   uint64
 	NeedsStackObjects  bool
 	Debug              bool // Whether to emit debug information in the LLVM module.
-	LLVMFeatures       string
 }

 // compilerContext contains function-independent data that should still be
@@ -186,12 +185,7 @@ func NewTargetMachine(config *Config) (llvm.TargetMachine, error) {
 	if err != nil {
 		return llvm.TargetMachine{}, err
 	}
-
-	feat := config.Features
-	if len(config.LLVMFeatures) > 0 {
-		feat = append(feat, config.LLVMFeatures)
-	}
-	features := strings.Join(feat, ",")
+	features := strings.Join(config.Features, ",")

 	var codeModel llvm.CodeModel
 	var relocationModel llvm.RelocMode
@@ -304,7 +298,7 @@ func CompilePackage(moduleName string, pkg *loader.Package, ssaPkg *ssa.Package,
 		c.dibuilder.Finalize()
 	}

-	return c.mod, c.diagnostics
+	return c.mod, nil
 }

 // getLLVMRuntimeType obtains a named type from the runtime package and returns
@@ -970,59 +964,11 @@ func (b *builder) createFunction() {
 	}
 }

-// posser is an interface that's implemented by both ssa.Value and
-// ssa.Instruction. It is implemented by everything that has a Pos() method,
-// which is all that getPos() needs.
-type posser interface {
-	Pos() token.Pos
-}
-
-// getPos returns position information for a ssa.Value or ssa.Instruction.
-//
-// Not all instructions have position information, especially when they're
-// implicit (such as implicit casts or implicit returns at the end of a
-// function). In these cases, it makes sense to try a bit harder to guess what
-// the position really should be.
-func getPos(val posser) token.Pos {
-	pos := val.Pos()
-	if pos != token.NoPos {
-		// Easy: position is known.
-		return pos
-	}
-
-	// No position information is known.
-	switch val := val.(type) {
-	case *ssa.MakeInterface:
-		return getPos(val.X)
-	case *ssa.Return:
-		syntax := val.Parent().Syntax()
-		if syntax != nil {
-			// non-synthetic
-			return syntax.End()
-		}
-		return token.NoPos
-	case *ssa.FieldAddr:
-		return getPos(val.X)
-	case *ssa.IndexAddr:
-		return getPos(val.X)
-	case *ssa.Slice:
-		return getPos(val.X)
-	case *ssa.Store:
-		return getPos(val.Addr)
-	case *ssa.Extract:
-		return getPos(val.Tuple)
-	default:
-		// This is reachable, for example with *ssa.Const, *ssa.If, and
-		// *ssa.Jump. They might be implemented in some way in the future.
-		return token.NoPos
-	}
-}
-
 // createInstruction builds the LLVM IR equivalent instructions for the
 // particular Go SSA instruction.
 func (b *builder) createInstruction(instr ssa.Instruction) {
 	if b.Debug {
-		pos := b.program.Fset.Position(getPos(instr))
+		pos := b.program.Fset.Position(instr.Pos())
 		b.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), b.difunc, llvm.Metadata{})
 	}

@@ -2312,20 +2258,14 @@ func (b *builder) createConst(prefix string, expr *ssa.Const) llvm.Value {
 		} else if typ.Info()&types.IsString != 0 {
 			str := constant.StringVal(expr.Value)
 			strLen := llvm.ConstInt(b.uintptrType, uint64(len(str)), false)
-			var strPtr llvm.Value
-			if str != "" {
-				objname := prefix + "$string"
-				global := llvm.AddGlobal(b.mod, llvm.ArrayType(b.ctx.Int8Type(), len(str)), objname)
-				global.SetInitializer(b.ctx.ConstString(str, false))
-				global.SetLinkage(llvm.InternalLinkage)
-				global.SetGlobalConstant(true)
-				global.SetUnnamedAddr(true)
-				global.SetAlignment(1)
-				zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
-				strPtr = b.CreateInBoundsGEP(global, []llvm.Value{zero, zero}, "")
-			} else {
-				strPtr = llvm.ConstNull(b.i8ptrType)
-			}
+			objname := prefix + "$string"
+			global := llvm.AddGlobal(b.mod, llvm.ArrayType(b.ctx.Int8Type(), len(str)), objname)
+			global.SetInitializer(b.ctx.ConstString(str, false))
+			global.SetLinkage(llvm.InternalLinkage)
+			global.SetGlobalConstant(true)
+			global.SetUnnamedAddr(true)
+			zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
+			strPtr := b.CreateInBoundsGEP(global, []llvm.Value{zero, zero}, "")
 			strObj := llvm.ConstNamedStruct(b.getLLVMRuntimeType("_string"), []llvm.Value{strPtr, strLen})
 			return strObj
 		} else if typ.Kind() == types.UnsafePointer {
@@ -32,7 +32,7 @@ func TestCompiler(t *testing.T) {
 		t.Skip("compiler tests require LLVM 11 or above, got LLVM ", llvm.Version)
 	}

-	target, err := compileopts.LoadTarget("wasm")
+	target, err := compileopts.LoadTarget("i686--linux")
 	if err != nil {
 		t.Fatal("failed to load target:", err)
 	}
@@ -62,7 +62,6 @@ func TestCompiler(t *testing.T) {
 		"string.go",
 		"float.go",
 		"interface.go",
-		"func.go",
 	}

 	for _, testCase := range tests {
@@ -85,16 +84,11 @@ func TestCompiler(t *testing.T) {
 			mod, errs := CompilePackage(testCase, pkg, program.Package(pkg.Pkg), machine, compilerConfig, false)
 			if errs != nil {
 				for _, err := range errs {
-					t.Error(err)
+					t.Log("error:", err)
 				}
 				return
 			}

-			err = llvm.VerifyModule(mod, llvm.PrintMessageAction)
-			if err != nil {
-				t.Error(err)
-			}
-
 			// Optimize IR a little.
 			funcPasses := llvm.NewFunctionPassManagerForModule(mod)
 			defer funcPasses.Dispose()
@@ -25,13 +25,14 @@ func (c *compilerContext) createFuncValue(builder llvm.Builder, funcPtr, context
 		// Closure is: {context, function pointer}
 		funcValueScalar = funcPtr
 	case "switch":
+		sigGlobal := c.getTypeCode(sig)
 		funcValueWithSignatureGlobalName := funcPtr.Name() + "$withSignature"
 		funcValueWithSignatureGlobal := c.mod.NamedGlobal(funcValueWithSignatureGlobalName)
 		if funcValueWithSignatureGlobal.IsNil() {
 			funcValueWithSignatureType := c.getLLVMRuntimeType("funcValueWithSignature")
 			funcValueWithSignature := llvm.ConstNamedStruct(funcValueWithSignatureType, []llvm.Value{
 				llvm.ConstPtrToInt(funcPtr, c.uintptrType),
-				c.getFuncSignatureID(sig),
+				sigGlobal,
 			})
 			funcValueWithSignatureGlobal = llvm.AddGlobal(c.mod, funcValueWithSignatureType, funcValueWithSignatureGlobalName)
 			funcValueWithSignatureGlobal.SetInitializer(funcValueWithSignature)
@@ -49,19 +50,6 @@ func (c *compilerContext) createFuncValue(builder llvm.Builder, funcPtr, context
 	return funcValue
 }

-// getFuncSignatureID returns a new external global for a given signature. This
-// global reference is not real, it is only used during func lowering to assign
-// signature types to functions and will then be removed.
-func (c *compilerContext) getFuncSignatureID(sig *types.Signature) llvm.Value {
-	sigGlobalName := "reflect/types.funcid:" + getTypeCodeName(sig)
-	sigGlobal := c.mod.NamedGlobal(sigGlobalName)
-	if sigGlobal.IsNil() {
-		sigGlobal = llvm.AddGlobal(c.mod, c.ctx.Int8Type(), sigGlobalName)
-		sigGlobal.SetGlobalConstant(true)
-	}
-	return sigGlobal
-}
-
 // extractFuncScalar returns some scalar that can be used in comparisons. It is
 // a cheap operation.
 func (b *builder) extractFuncScalar(funcValue llvm.Value) llvm.Value {
@@ -83,7 +71,7 @@ func (b *builder) decodeFuncValue(funcValue llvm.Value, sig *types.Signature) (f
 		funcPtr = b.CreateExtractValue(funcValue, 1, "")
 	case "switch":
 		llvmSig := b.getRawFuncType(sig)
-		sigGlobal := b.getFuncSignatureID(sig)
+		sigGlobal := b.getTypeCode(sig)
 		funcPtr = b.createRuntimeCall("getFuncPtr", []llvm.Value{funcValue, sigGlobal}, "")
 		funcPtr = b.CreateIntToPtr(funcPtr, llvmSig, "")
 	default:
@@ -34,9 +34,6 @@ func (b *builder) createGoInstruction(funcPtr llvm.Value, params []llvm.Value, p
 		} else {
 			// The stack size is fixed at compile time. By emitting it here as a
 			// constant, it can be optimized.
-			if b.DefaultStackSize == 0 {
-				b.addError(pos, "default stack size for goroutines is not set")
-			}
 			stackSize = llvm.ConstInt(b.uintptrType, b.DefaultStackSize, false)
 		}
 	case "coroutines":
@@ -46,7 +46,6 @@ func (c *compilerContext) getTypeCode(typ types.Type) llvm.Value {
 		var references llvm.Value
 		var length int64
 		var methodSet llvm.Value
-		var ptrTo llvm.Value
 		switch typ := typ.(type) {
 		case *types.Named:
 			references = c.getTypeCode(typ.Underlying())
@@ -70,25 +69,22 @@ func (c *compilerContext) getTypeCode(typ types.Type) llvm.Value {
 		if _, ok := typ.Underlying().(*types.Interface); !ok {
 			methodSet = c.getTypeMethodSet(typ)
 		}
-		if _, ok := typ.Underlying().(*types.Pointer); !ok {
-			ptrTo = c.getTypeCode(types.NewPointer(typ))
+		if !references.IsNil() || length != 0 || !methodSet.IsNil() {
+			// Set the 'references' field of the runtime.typecodeID struct.
+			globalValue := llvm.ConstNull(global.Type().ElementType())
+			if !references.IsNil() {
+				globalValue = llvm.ConstInsertValue(globalValue, references, []uint32{0})
+			}
+			if length != 0 {
+				lengthValue := llvm.ConstInt(c.uintptrType, uint64(length), false)
+				globalValue = llvm.ConstInsertValue(globalValue, lengthValue, []uint32{1})
+			}
+			if !methodSet.IsNil() {
+				globalValue = llvm.ConstInsertValue(globalValue, methodSet, []uint32{2})
+			}
+			global.SetInitializer(globalValue)
+			global.SetLinkage(llvm.LinkOnceODRLinkage)
 		}
-		globalValue := llvm.ConstNull(global.Type().ElementType())
-		if !references.IsNil() {
-			globalValue = llvm.ConstInsertValue(globalValue, references, []uint32{0})
-		}
-		if length != 0 {
-			lengthValue := llvm.ConstInt(c.uintptrType, uint64(length), false)
-			globalValue = llvm.ConstInsertValue(globalValue, lengthValue, []uint32{1})
-		}
-		if !methodSet.IsNil() {
-			globalValue = llvm.ConstInsertValue(globalValue, methodSet, []uint32{2})
-		}
-		if !ptrTo.IsNil() {
-			globalValue = llvm.ConstInsertValue(globalValue, ptrTo, []uint32{3})
-		}
-		global.SetInitializer(globalValue)
-		global.SetLinkage(llvm.LinkOnceODRLinkage)
 		global.SetGlobalConstant(true)
 	}
 	return global
@@ -345,7 +341,7 @@ func (b *builder) createTypeAssert(expr *ssa.TypeAssert) llvm.Value {
 		commaOk = b.createRuntimeCall("interfaceImplements", []llvm.Value{actualTypeNum, methodSet}, "")

 	} else {
-		globalName := "reflect/types.typeid:" + getTypeCodeName(expr.AssertedType)
+		globalName := "reflect/types.type:" + getTypeCodeName(expr.AssertedType) + "$id"
 		assertedTypeCodeGlobal := b.mod.NamedGlobal(globalName)
 		if assertedTypeCodeGlobal.IsNil() {
 			// Create a new typecode global.
@@ -139,17 +139,6 @@ func (c *compilerContext) getFunction(fn *ssa.Function) llvm.Value {
 		for _, attrName := range []string{"noalias", "nonnull"} {
 			llvmFn.AddAttributeAtIndex(0, c.ctx.CreateEnumAttribute(llvm.AttributeKindID(attrName), 0))
 		}
-	case "runtime.sliceAppend":
-		// Appending a slice will only read the to-be-appended slice, it won't
-		// be modified.
-		llvmFn.AddAttributeAtIndex(2, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
-		llvmFn.AddAttributeAtIndex(2, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("readonly"), 0))
-	case "runtime.sliceCopy":
-		// Copying a slice won't capture any of the parameters.
-		llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("writeonly"), 0))
-		llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
-		llvmFn.AddAttributeAtIndex(2, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("readonly"), 0))
-		llvmFn.AddAttributeAtIndex(2, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
 	case "runtime.trackPointer":
 		// This function is necessary for tracking pointers on the stack in a
 		// portable way (see gc_stack_portable.go). Indicate to the optimizer
@@ -366,18 +355,16 @@ func (c *compilerContext) getGlobal(g *ssa.Global) llvm.Value {

 		// Set alignment from the //go:align comment.
 		var alignInBits uint32
-		alignment := c.targetData.ABITypeAlignment(llvmType)
-		if info.align > alignment {
-			alignment = info.align
-		}
-		if alignment <= 0 || alignment&(alignment-1) != 0 {
+		if info.align < 0 || info.align&(info.align-1) != 0 {
 			// Check for power-of-two (or 0).
 			// See: https://stackoverflow.com/a/108360
 			c.addError(g.Pos(), "global variable alignment must be a positive power of two")
 		} else {
 			// Set the alignment only when it is a power of two.
-			alignInBits = uint32(alignment) ^ uint32(alignment-1)
-			llvmGlobal.SetAlignment(alignment)
+			alignInBits = uint32(info.align) ^ uint32(info.align-1)
+			if info.align > c.targetData.ABITypeAlignment(llvmType) {
+				llvmGlobal.SetAlignment(info.align)
+			}
 		}

 		if c.Debug && !info.extern {
@@ -1,7 +1,7 @@
 ; ModuleID = 'basic.go'
 source_filename = "basic.go"
-target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
-target triple = "wasm32--wasi"
+target datalayout = "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:32-n8:16:32-S128"
+target triple = "i686--linux"

 declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)

@@ -1,7 +1,7 @@
 ; ModuleID = 'float.go'
 source_filename = "float.go"
-target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
-target triple = "wasm32--wasi"
+target datalayout = "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:32-n8:16:32-S128"
+target triple = "i686--linux"

 declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)

@@ -1,12 +0,0 @@
-package main
-
-func foo(callback func(int)) {
-	callback(3)
-}
-
-func bar() {
-	foo(someFunc)
-}
-
-func someFunc(int) {
-}
@@ -1,47 +0,0 @@
-; ModuleID = 'func.go'
-source_filename = "func.go"
-target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
-target triple = "wasm32--wasi"
-
-%runtime.funcValueWithSignature = type { i32, i8* }
-
-@"reflect/types.funcid:func:{basic:int}{}" = external constant i8
-@"main.someFunc$withSignature" = linkonce_odr constant %runtime.funcValueWithSignature { i32 ptrtoint (void (i32, i8*, i8*)* @main.someFunc to i32), i8* @"reflect/types.funcid:func:{basic:int}{}" }
-
-declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)
-
-define hidden void @main.init(i8* %context, i8* %parentHandle) unnamed_addr {
-entry:
-  ret void
-}
-
-define hidden void @main.foo(i8* %callback.context, i32 %callback.funcptr, i8* %context, i8* %parentHandle) unnamed_addr {
-entry:
-  %0 = call i32 @runtime.getFuncPtr(i8* %callback.context, i32 %callback.funcptr, i8* nonnull @"reflect/types.funcid:func:{basic:int}{}", i8* undef, i8* null)
-  %1 = icmp eq i32 %0, 0
-  br i1 %1, label %fpcall.throw, label %fpcall.next
-
-fpcall.throw:                                     ; preds = %entry
-  call void @runtime.nilPanic(i8* undef, i8* null)
-  unreachable
-
-fpcall.next:                                      ; preds = %entry
-  %2 = inttoptr i32 %0 to void (i32, i8*, i8*)*
-  call void %2(i32 3, i8* %callback.context, i8* undef)
-  ret void
-}
-
-declare i32 @runtime.getFuncPtr(i8*, i32, i8* dereferenceable_or_null(1), i8*, i8*)
-
-declare void @runtime.nilPanic(i8*, i8*)
-
-define hidden void @main.bar(i8* %context, i8* %parentHandle) unnamed_addr {
-entry:
-  call void @main.foo(i8* undef, i32 ptrtoint (%runtime.funcValueWithSignature* @"main.someFunc$withSignature" to i32), i8* undef, i8* undef)
-  ret void
-}
-
-define hidden void @main.someFunc(i32 %arg0, i8* %context, i8* %parentHandle) unnamed_addr {
-entry:
-  ret void
-}
@@ -1,26 +1,25 @@
 ; ModuleID = 'interface.go'
 source_filename = "interface.go"
-target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
-target triple = "wasm32--wasi"
+target datalayout = "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:32-n8:16:32-S128"
+target triple = "i686--linux"

-%runtime.typecodeID = type { %runtime.typecodeID*, i32, %runtime.interfaceMethodInfo*, %runtime.typecodeID* }
+%runtime.typecodeID = type { %runtime.typecodeID*, i32, %runtime.interfaceMethodInfo* }
 %runtime.interfaceMethodInfo = type { i8*, i32 }
 %runtime._interface = type { i32, i8* }
 %runtime._string = type { i8*, i32 }

-@"reflect/types.type:basic:int" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* null, i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* @"reflect/types.type:pointer:basic:int" }
-@"reflect/types.type:pointer:basic:int" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:basic:int", i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* null }
-@"reflect/types.type:pointer:named:error" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:named:error", i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* null }
-@"reflect/types.type:named:error" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:interface:{Error:func:{}{basic:string}}", i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* @"reflect/types.type:pointer:named:error" }
-@"reflect/types.type:interface:{Error:func:{}{basic:string}}" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* bitcast ([1 x i8*]* @"reflect/types.interface:interface{Error() string}$interface" to %runtime.typecodeID*), i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* @"reflect/types.type:pointer:interface:{Error:func:{}{basic:string}}" }
+@"reflect/types.type:basic:int" = linkonce_odr constant %runtime.typecodeID zeroinitializer
+@"reflect/types.type:pointer:basic:int" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:basic:int", i32 0, %runtime.interfaceMethodInfo* null }
+@"reflect/types.type:pointer:named:error" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:named:error", i32 0, %runtime.interfaceMethodInfo* null }
+@"reflect/types.type:named:error" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:interface:{Error:func:{}{basic:string}}", i32 0, %runtime.interfaceMethodInfo* null }
+@"reflect/types.type:interface:{Error:func:{}{basic:string}}" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* bitcast ([1 x i8*]* @"reflect/types.interface:interface{Error() string}$interface" to %runtime.typecodeID*), i32 0, %runtime.interfaceMethodInfo* null }
@"func Error() string" = external constant i8
@"reflect/types.interface:interface{Error() string}$interface" = linkonce_odr constant [1 x i8*] [i8* @"func Error() string"]
-@"reflect/types.type:pointer:interface:{Error:func:{}{basic:string}}" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:interface:{Error:func:{}{basic:string}}", i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* null }
-@"reflect/types.type:pointer:interface:{String:func:{}{basic:string}}" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:interface:{String:func:{}{basic:string}}", i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* null }
-@"reflect/types.type:interface:{String:func:{}{basic:string}}" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* bitcast ([1 x i8*]* @"reflect/types.interface:interface{String() string}$interface" to %runtime.typecodeID*), i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* @"reflect/types.type:pointer:interface:{String:func:{}{basic:string}}" }
+@"reflect/types.type:pointer:interface:{String:func:{}{basic:string}}" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:interface:{String:func:{}{basic:string}}", i32 0, %runtime.interfaceMethodInfo* null }
+@"reflect/types.type:interface:{String:func:{}{basic:string}}" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* bitcast ([1 x i8*]* @"reflect/types.interface:interface{String() string}$interface" to %runtime.typecodeID*), i32 0, %runtime.interfaceMethodInfo* null }
@"func String() string" = external constant i8
@"reflect/types.interface:interface{String() string}$interface" = linkonce_odr constant [1 x i8*] [i8* @"func String() string"]
-@"reflect/types.typeid:basic:int" = external constant i8
+@"reflect/types.type:basic:int$id" = external constant i8
@"error$interface" = linkonce_odr constant [1 x i8*] [i8* @"func Error() string"]

 declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)
@@ -52,7 +51,7 @@ entry:

 define hidden i1 @main.isInt(i32 %itf.typecode, i8* %itf.value, i8* %context, i8* %parentHandle) unnamed_addr {
 entry:
-  %typecode = call i1 @runtime.typeAssert(i32 %itf.typecode, i8* nonnull @"reflect/types.typeid:basic:int", i8* undef, i8* null)
+  %typecode = call i1 @runtime.typeAssert(i32 %itf.typecode, i8* nonnull @"reflect/types.type:basic:int$id", i8* undef, i8* null)
  br i1 %typecode, label %typeassert.ok, label %typeassert.next

 typeassert.ok:                                    ; preds = %entry
@@ -1,7 +1,7 @@
 ; ModuleID = 'pointer.go'
 source_filename = "pointer.go"
-target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
-target triple = "wasm32--wasi"
+target datalayout = "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:32-n8:16:32-S128"
+target triple = "i686--linux"

 declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)

@@ -1,7 +1,7 @@
 ; ModuleID = 'slice.go'
 source_filename = "slice.go"
-target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
-target triple = "wasm32--wasi"
+target datalayout = "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:32-n8:16:32-S128"
+target triple = "i686--linux"

 declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)

@@ -60,7 +60,7 @@ entry:
  ret { i32*, i32, i32 } %7
 }

-declare { i8*, i32, i32 } @runtime.sliceAppend(i8*, i8* nocapture readonly, i32, i32, i32, i32, i8*, i8*)
+declare { i8*, i32, i32 } @runtime.sliceAppend(i8*, i8*, i32, i32, i32, i32, i8*, i8*)

 define hidden { i32*, i32, i32 } @main.sliceAppendSlice(i32* %ints.data, i32 %ints.len, i32 %ints.cap, i32* %added.data, i32 %added.len, i32 %added.cap, i8* %context, i8* %parentHandle) unnamed_addr {
 entry:
@@ -85,4 +85,4 @@ entry:
  ret i32 %copy.n
 }

-declare i32 @runtime.sliceCopy(i8* nocapture writeonly, i8* nocapture readonly, i32, i32, i32, i8*, i8*)
+declare i32 @runtime.sliceCopy(i8*, i8*, i32, i32, i32, i8*, i8*)
@@ -1,13 +1,5 @@
 package main

-func someString() string {
-	return "foo"
-}
-
-func zeroLengthString() string {
-	return ""
-}
-
 func stringLen(s string) int {
 	return len(s)
 }
@@ -1,11 +1,7 @@
 ; ModuleID = 'string.go'
 source_filename = "string.go"
-target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
-target triple = "wasm32--wasi"
-
-%runtime._string = type { i8*, i32 }
-
-@"main.someString$string" = internal unnamed_addr constant [3 x i8] c"foo", align 1
+target datalayout = "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:32-n8:16:32-S128"
+target triple = "i686--linux"

 declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)

@@ -14,16 +10,6 @@ entry:
  ret void
 }

-define hidden %runtime._string @main.someString(i8* %context, i8* %parentHandle) unnamed_addr {
-entry:
-  ret %runtime._string { i8* getelementptr inbounds ([3 x i8], [3 x i8]* @"main.someString$string", i32 0, i32 0), i32 3 }
-}
-
-define hidden %runtime._string @main.zeroLengthString(i8* %context, i8* %parentHandle) unnamed_addr {
-entry:
-  ret %runtime._string zeroinitializer
-}
-
 define hidden i32 @main.stringLen(i8* %s.data, i32 %s.len, i8* %context, i8* %parentHandle) unnamed_addr {
 entry:
  ret i32 %s.len
@@ -12,5 +12,5 @@ require (
 	go.bug.st/serial v1.1.2
 	golang.org/x/sys v0.0.0-20210113181707-4bcb84eeeb78
 	golang.org/x/tools v0.0.0-20200216192241-b320d3a0f5a2
-	tinygo.org/x/go-llvm v0.0.0-20210325115028-e7b85195e81c
+	tinygo.org/x/go-llvm v0.0.0-20210308112806-9ef958b6bed4
 )
@@ -59,5 +59,3 @@ gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 tinygo.org/x/go-llvm v0.0.0-20210308112806-9ef958b6bed4 h1:CMUHxVTb+UuUePuMf8vkWjZ3gTp9BBK91KrgOCwoNHs=
 tinygo.org/x/go-llvm v0.0.0-20210308112806-9ef958b6bed4/go.mod h1:fv1F0BSNpxMfCL0zF3M4OPFbgYHnhtB6ST0HvUtu/LE=
-tinygo.org/x/go-llvm v0.0.0-20210325115028-e7b85195e81c h1:vn9IPshzYmzZis10UEVrsIBRv9FpykADw6M3/tHHROg=
-tinygo.org/x/go-llvm v0.0.0-20210325115028-e7b85195e81c/go.mod h1:fv1F0BSNpxMfCL0zF3M4OPFbgYHnhtB6ST0HvUtu/LE=
@@ -171,9 +171,8 @@ func getGoroot() string {
 	switch runtime.GOOS {
 	case "linux":
 		candidates = []string{
-			"/usr/local/go",     // manually installed
-			"/usr/lib/go",       // from the distribution
-			"/snap/go/current/", // installed using snap
+			"/usr/local/go", // manually installed
+			"/usr/lib/go",   // from the distribution
 		}
 	case "darwin":
 		candidates = []string{
@@ -25,7 +25,6 @@ type function struct {
 // basicBlock represents a LLVM basic block and contains a slice of
 // instructions. The last instruction must be a terminator instruction.
 type basicBlock struct {
-	phiNodes     []instruction
 	instructions []instruction
 }

@@ -136,15 +135,6 @@ func (r *runner) compileFunction(llvmFn llvm.Value) *function {
 				default:
 					panic("unknown number of operands")
 				}
-			case llvm.Switch:
-				// A switch is an array of (value, label) pairs, of which the
-				// first one indicates the to-switch value and the default
-				// label.
-				numOperands := llvmInst.OperandsCount()
-				for i := 0; i < numOperands; i += 2 {
-					inst.operands = append(inst.operands, r.getValue(llvmInst.Operand(i)))
-					inst.operands = append(inst.operands, literalValue{uint32(blockIndices[llvmInst.Operand(i+1)])})
-				}
 			case llvm.PHI:
 				inst.name = llvmInst.Name()
 				incomingCount := inst.llvmInst.IncomingCount()
@@ -347,13 +337,7 @@ func (r *runner) compileFunction(llvmFn llvm.Value) *function {
 				// This error is handled when actually trying to interpret this
 				// instruction (to not trigger on code that won't be executed).
 			}
-			if inst.opcode == llvm.PHI {
-				// PHI nodes need to be treated specially, see the comment in
-				// interpreter.go for an explanation.
-				bb.phiNodes = append(bb.phiNodes, inst)
-			} else {
-				bb.instructions = append(bb.instructions, inst)
-			}
+			bb.instructions = append(bb.instructions, inst)
 		}
 	}
 	return fn
@@ -13,9 +13,9 @@ import (
 func TestInterp(t *testing.T) {
 	for _, name := range []string{
 		"basic",
-		"phi",
 		"slice-copy",
 		"consteval",
+		"map",
 		"interface",
 	} {
 		name := name // make tc local to this closure
@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"math"
 	"os"
-	"strconv"
 	"strings"
 	"time"

@@ -34,50 +33,6 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 	lastBB := -1 // last basic block is undefined, only defined after a branch
 	var operands []value
 	for instIndex := 0; instIndex < len(bb.instructions); instIndex++ {
-		if instIndex == 0 {
-			// This is the start of a new basic block.
-			// There may be PHI nodes that need to be resolved. Resolve all PHI
-			// nodes before continuing with regular instructions.
-			// PHI nodes need to be treated specially because they can have a
-			// mutual dependency:
-			//   for.loop:
-			//     %a = phi i8 [ 1, %entry ], [ %b, %for.loop ]
-			//     %b = phi i8 [ 3, %entry ], [ %a, %for.loop ]
-			// If these PHI nodes are processed like a regular instruction, %a
-			// and %b are both 3 on the second iteration of the loop because %b
-			// loads the value of %a from the second iteration, while it should
-			// load the value from the previous iteration. The correct behavior
-			// is that these two values swap each others place on each
-			// iteration.
-			var phiValues []value
-			var phiIndices []int
-			for _, inst := range bb.phiNodes {
-				var result value
-				for i := 0; i < len(inst.operands); i += 2 {
-					if int(inst.operands[i].(literalValue).value.(uint32)) == lastBB {
-						incoming := inst.operands[i+1]
-						if local, ok := incoming.(localValue); ok {
-							result = locals[fn.locals[local.value]]
-						} else {
-							result = incoming
-						}
-						break
-					}
-				}
-				if r.debug {
-					fmt.Fprintln(os.Stderr, indent+"phi", inst.operands, "->", result)
-				}
-				if result == nil {
-					panic("could not find PHI input")
-				}
-				phiValues = append(phiValues, result)
-				phiIndices = append(phiIndices, inst.localIndex)
-			}
-			for i, value := range phiValues {
-				locals[phiIndices[i]] = value
-			}
-		}
-
 		inst := bb.instructions[instIndex]
 		operands = operands[:0]
 		isRuntimeInst := false
@@ -148,24 +103,27 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 			default:
 				panic("unknown operands length")
 			}
-		case llvm.Switch:
-			// Switch statement: [value, defaultLabel, case0, label0, case1, label1, ...]
-			value := operands[0].Uint()
-			targetLabel := operands[1].Uint() // default label
-			// Do a lazy switch by iterating over all cases.
-			for i := 2; i < len(operands); i += 2 {
-				if value == operands[i].Uint() {
-					targetLabel = operands[i+1].Uint()
+			break // continue with next block
+		case llvm.PHI:
+			var result value
+			for i := 0; i < len(inst.operands); i += 2 {
+				if int(inst.operands[i].(literalValue).value.(uint32)) == lastBB {
+					incoming := inst.operands[i+1]
+					if local, ok := incoming.(localValue); ok {
+						result = locals[fn.locals[local.value]]
+					} else {
+						result = incoming
+					}
 					break
 				}
 			}
-			lastBB = currentBB
-			currentBB = int(targetLabel)
-			bb = fn.blocks[currentBB]
-			instIndex = -1 // start at 0 the next cycle
 			if r.debug {
-				fmt.Fprintln(os.Stderr, indent+"switch", operands, "->", currentBB)
+				fmt.Fprintln(os.Stderr, indent+"phi", inst.operands, "->", result)
 			}
+			if result == nil {
+				panic("could not find PHI input")
+			}
+			locals[inst.localIndex] = result
 		case llvm.Select:
 			// Select is much like a ternary operator: it picks a result from
 			// the second and third operand based on the boolean first operand.
@@ -197,7 +155,7 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 				// which case this call won't even get to this point but will
 				// already be emitted in initAll.
 				continue
-			case strings.HasPrefix(callFn.name, "runtime.print") || callFn.name == "runtime._panic" || callFn.name == "runtime.hashmapGet" || callFn.name == "os.runtime_args":
+			case strings.HasPrefix(callFn.name, "runtime.print") || callFn.name == "runtime._panic" || callFn.name == "runtime.hashmapGet":
 				// These functions should be run at runtime. Specifically:
 				//   * Print and panic functions are best emitted directly without
 				//     interpreting them, otherwise we get a ton of putchar (etc.)
@@ -205,9 +163,6 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 				//   * runtime.hashmapGet tries to access the map value directly.
 				//     This is not possible as the map value is treated as a special
 				//     kind of object in this package.
-				//   * os.runtime_args reads globals that are initialized outside
-				//     the view of the interp package so it always needs to be run
-				//     at runtime.
 				err := r.runAtRuntime(fn, inst, locals, &mem, indent)
 				if err != nil {
 					return nil, mem, err
@@ -373,7 +328,7 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 					return nil, mem, r.errorAt(inst, err)
 				}
 				actualType := actualTypePtrToInt.Operand(0)
-				if strings.TrimPrefix(actualType.Name(), "reflect/types.type:") == strings.TrimPrefix(assertedType.Name(), "reflect/types.typeid:") {
+				if actualType.Name()+"$id" == assertedType.Name() {
 					locals[inst.localIndex] = literalValue{uint8(1)}
 				} else {
 					locals[inst.localIndex] = literalValue{uint8(0)}
@@ -460,6 +415,74 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 					return nil, mem, r.errorAt(inst, errors.New("could not find method: "+signature.Name()))
 				}
 				locals[inst.localIndex] = r.getValue(method)
+			case callFn.name == "runtime.hashmapMake":
+				// Create a new map.
+				hashmapPointerType := inst.llvmInst.Type()
+				keySize := uint32(operands[1].Uint())
+				valueSize := uint32(operands[2].Uint())
+				m := newMapValue(r, hashmapPointerType, keySize, valueSize)
+				alloc := object{
+					llvmType:   hashmapPointerType,
+					globalName: r.pkgName + "$map",
+					buffer:     m,
+					size:       m.len(r),
+				}
+				index := len(r.objects)
+				r.objects = append(r.objects, alloc)
+
+				// Create a pointer to this map. Maps are reference types, so
+				// are implemented as pointers.
+				ptr := newPointerValue(r, index, 0)
+				if r.debug {
+					fmt.Fprintln(os.Stderr, indent+"runtime.hashmapMake:", keySize, valueSize, "->", ptr)
+				}
+				locals[inst.localIndex] = ptr
+			case callFn.name == "runtime.hashmapBinarySet":
+				// Do a mapassign operation with a binary key (that is, without
+				// a string key).
+				if r.debug {
+					fmt.Fprintln(os.Stderr, indent+"runtime.hashmapBinarySet:", operands[1:])
+				}
+				mapPtr, err := operands[1].asPointer(r)
+				if err != nil {
+					return nil, mem, r.errorAt(inst, err)
+				}
+				m := mem.getWritable(mapPtr.index()).buffer.(*mapValue)
+				keyPtr, err := operands[2].asPointer(r)
+				if err != nil {
+					return nil, mem, r.errorAt(inst, err)
+				}
+				valuePtr, err := operands[3].asPointer(r)
+				if err != nil {
+					return nil, mem, r.errorAt(inst, err)
+				}
+				err = m.putBinary(&mem, keyPtr, valuePtr)
+				if err != nil {
+					return nil, mem, r.errorAt(inst, err)
+				}
+			case callFn.name == "runtime.hashmapStringSet":
+				// Do a mapassign operation with a string key.
+				if r.debug {
+					fmt.Fprintln(os.Stderr, indent+"runtime.hashmapBinarySet:", operands[1:])
+				}
+				mapPtr, err := operands[1].asPointer(r)
+				if err != nil {
+					return nil, mem, r.errorAt(inst, err)
+				}
+				m := mem.getWritable(mapPtr.index()).buffer.(*mapValue)
+				stringPtr, err := operands[2].asPointer(r)
+				if err != nil {
+					return nil, mem, r.errorAt(inst, err)
+				}
+				stringLen := operands[3].Uint()
+				valuePtr, err := operands[4].asPointer(r)
+				if err != nil {
+					return nil, mem, r.errorAt(inst, err)
+				}
+				err = m.putString(&mem, stringPtr, stringLen, valuePtr)
+				if err != nil {
+					return nil, mem, r.errorAt(inst, err)
+				}
 			default:
 				if len(callFn.blocks) == 0 {
 					// Call to a function declaration without a definition
@@ -931,31 +954,16 @@ func (r *runner) runAtRuntime(fn *function, inst instruction, locals []value, me
 		result = r.builder.CreateBitCast(operands[0], inst.llvmInst.Type(), inst.name)
 	case llvm.ExtractValue:
 		indices := inst.llvmInst.Indices()
-		// Note: the Go LLVM API doesn't support multiple indices, so simulate
-		// this operation with some extra extractvalue instructions. Hopefully
-		// this is optimized to a single instruction.
-		agg := operands[0]
-		for i := 0; i < len(indices)-1; i++ {
-			agg = r.builder.CreateExtractValue(agg, int(indices[i]), inst.name+".agg")
+		if len(indices) != 1 {
+			panic("expected exactly one index")
 		}
-		result = r.builder.CreateExtractValue(agg, int(indices[len(indices)-1]), inst.name)
+		result = r.builder.CreateExtractValue(operands[0], int(indices[0]), inst.name)
 	case llvm.InsertValue:
 		indices := inst.llvmInst.Indices()
-		// Similar to extractvalue, we're working around a limitation in the Go
-		// LLVM API here by splitting the insertvalue into multiple instructions
-		// if there is more than one operand.
-		agg := operands[0]
-		aggregates := []llvm.Value{agg}
-		for i := 0; i < len(indices)-1; i++ {
-			agg = r.builder.CreateExtractValue(agg, int(indices[i]), inst.name+".agg"+strconv.Itoa(i))
-			aggregates = append(aggregates, agg)
+		if len(indices) != 1 {
+			panic("expected exactly one index")
 		}
-		result = operands[1]
-		for i := len(indices) - 1; i >= 0; i-- {
-			agg := aggregates[i]
-			result = r.builder.CreateInsertValue(agg, result, int(indices[i]), inst.name+".insertvalue"+strconv.Itoa(i))
-		}
-
+		result = r.builder.CreateInsertValue(operands[0], operands[1], int(indices[0]), inst.name)
 	case llvm.Add:
 		result = r.builder.CreateAdd(operands[0], operands[1], inst.name)
 	case llvm.Sub:
@@ -640,6 +640,288 @@ func (v pointerValue) toLLVMValue(llvmType llvm.Type, mem *memoryView) (llvm.Val
 	return gep, nil
 }

+// mapValue implements a Go map which is created at compile time and stored as a
+// global variable.
+// The value itself is only used as part of an object (object.buffer). Maps are
+// reference types aka pointers, so it can only be used as a pointerValue, not
+// directly.
+type mapValue struct {
+	r           *runner
+	pkgName     string
+	size        uint32 // byte size of runtime.hashmap
+	hashmap     llvm.Value
+	keyIsString bool
+	keys        []interface{} // either rawValue (for binary key) or mapStringKey (for string key)
+	values      []rawValue
+	keySize     uint32
+	valueSize   uint32
+}
+
+type mapStringKey struct {
+	buf  pointerValue
+	size uint64
+	data []uint64
+}
+
+func newMapValue(r *runner, hashmapPointerType llvm.Type, keySize, valueSize uint32) *mapValue {
+	size := uint32(r.targetData.TypeAllocSize(hashmapPointerType.ElementType()))
+	return &mapValue{
+		r:         r,
+		pkgName:   r.pkgName,
+		size:      size,
+		keySize:   keySize,
+		valueSize: valueSize,
+	}
+}
+
+func (v *mapValue) len(r *runner) uint32 {
+	return v.size
+}
+
+func (v *mapValue) clone() value {
+	// Return a copy of mapValue.
+	clone := *v
+	clone.keys = append([]interface{}{}, clone.keys...)
+	clone.values = append([]rawValue{}, clone.values...)
+	return &clone
+}
+
+func (v *mapValue) asPointer(r *runner) (pointerValue, error) {
+	panic("interp: mapValue.asPointer")
+}
+
+func (v *mapValue) asRawValue(r *runner) rawValue {
+	panic("interp: mapValue.asRawValue")
+}
+
+func (v *mapValue) Uint() uint64 {
+	panic("interp: mapValue.Uint")
+}
+
+func (v *mapValue) Int() int64 {
+	panic("interp: mapValue.Int")
+}
+
+// Temporary struct to collect data before turning this into a hashmap bucket
+// LLVM value.
+type mapBucket struct {
+	m       *mapValue
+	tophash [8]uint8
+	keys    []rawValue // can have up to 8 keys
+	values  []rawValue // can have up to 8 values, len(keys) == len(values)
+}
+
+// create returns a (pointer to a) buffer structurally equivalent to
+// runtime.hashmapBucket.
+func (b *mapBucket) create(ctx llvm.Context, nextBucket llvm.Value, mem *memoryView) llvm.Value {
+	// Create tophash array.
+	int8Type := ctx.Int8Type()
+	tophashValues := make([]llvm.Value, 8)
+	for i := range tophashValues {
+		tophashValues[i] = llvm.ConstInt(int8Type, uint64(b.tophash[i]), false)
+	}
+	tophash := llvm.ConstArray(int8Type, tophashValues)
+
+	// Create next pointer (if not set).
+	if nextBucket.IsNil() {
+		nextBucket = llvm.ConstNull(llvm.PointerType(int8Type, 0))
+	}
+
+	// Create data for keys.
+	var keyValues []llvm.Value
+	for _, key := range b.keys {
+		keyValue, err := key.rawLLVMValue(mem)
+		if err != nil {
+			panic(err)
+		}
+		keyValues = append(keyValues, keyValue)
+	}
+	if len(b.keys) < 8 {
+		keyValues = append(keyValues, llvm.ConstNull(llvm.ArrayType(int8Type, int(b.m.keySize)*(8-len(b.keys)))))
+	}
+	keyValue := ctx.ConstStruct(keyValues, false)
+	if checks && uint32(b.m.r.targetData.TypeAllocSize(keyValue.Type())) != b.m.keySize*8 {
+		panic("key size invalid")
+	}
+
+	// Create data for values.
+	var valueValues []llvm.Value
+	for _, value := range b.values {
+		v, err := value.rawLLVMValue(mem)
+		if err != nil {
+			panic(err)
+		}
+		valueValues = append(valueValues, v)
+	}
+	if len(b.values) < 8 {
+		valueValues = append(valueValues, llvm.ConstNull(llvm.ArrayType(int8Type, int(b.m.valueSize)*(8-len(b.values)))))
+	}
+	valueValue := ctx.ConstStruct(valueValues, false)
+	if checks && uint32(b.m.r.targetData.TypeAllocSize(valueValue.Type())) != b.m.valueSize*8 {
+		panic("value size invalid")
+	}
+
+	// Create the bucket.
+	bucketInitializer := ctx.ConstStruct([]llvm.Value{
+		tophash,
+		nextBucket,
+		keyValue,
+		valueValue,
+	}, false)
+	bucket := llvm.AddGlobal(b.m.r.mod, bucketInitializer.Type(), b.m.pkgName+"$mapbucket")
+	bucket.SetInitializer(bucketInitializer)
+	bucket.SetLinkage(llvm.InternalLinkage)
+	bucket.SetUnnamedAddr(true)
+	return bucket
+}
+
+func (v *mapValue) toLLVMValue(hashmapType llvm.Type, mem *memoryView) (llvm.Value, error) {
+	if !v.hashmap.IsNil() {
+		return v.hashmap, nil
+	}
+
+	// Create a slice of buckets with all the keys and values in the hashmap.
+	var buckets []*mapBucket
+	var bucket *mapBucket
+	for i, key := range v.keys {
+		var data []uint64
+		var keyValue rawValue
+		switch key := key.(type) {
+		case mapStringKey:
+			data = key.data
+			keyValue = newRawValue(v.keySize)
+			// runtime._string is {ptr, length}
+			for i := uint32(0); i < v.keySize/2; i++ {
+				keyValue.buf[i] = key.buf.pointer
+			}
+			copy(keyValue.buf[v.keySize/2:], literalValue{key.size}.asRawValue(v.r).buf)
+		case rawValue:
+			if key.hasPointer() {
+				return llvm.Value{}, errors.New("interp: todo: map key with pointer")
+			}
+			data = key.buf
+			keyValue = key
+		default:
+			return llvm.Value{}, errors.New("interp: unknown map key type")
+		}
+		buf := make([]byte, len(data))
+		for i, p := range data {
+			buf[i] = byte(p)
+		}
+		hash := v.hash(buf)
+
+		if i%8 == 0 {
+			bucket = &mapBucket{m: v}
+			buckets = append(buckets, bucket)
+		}
+		bucket.tophash[i%8] = v.topHash(hash)
+		bucket.keys = append(bucket.keys, keyValue)
+		bucket.values = append(bucket.values, v.values[i])
+	}
+
+	// Convert these buckets into LLVM global variables.
+	ctx := v.r.mod.Context()
+	var nextBucket llvm.Value
+	for i := len(buckets) - 1; i >= 0; i-- {
+		bucket = buckets[i]
+		bucketValue := bucket.create(ctx, nextBucket, mem)
+		nextBucket = bucketValue
+	}
+	firstBucket := nextBucket
+	if firstBucket.IsNil() {
+		firstBucket = llvm.ConstNull(mem.r.i8ptrType)
+	} else {
+		firstBucket = llvm.ConstBitCast(firstBucket, mem.r.i8ptrType)
+	}
+
+	// Create the hashmap itself, pointing to these buckets.
+	hashmapPointerType := llvm.PointerType(hashmapType, 0)
+	hashmap := llvm.ConstNamedStruct(hashmapType, []llvm.Value{
+		llvm.ConstPointerNull(hashmapPointerType), // next
+		firstBucket, // buckets
+		llvm.ConstInt(hashmapType.StructElementTypes()[2], uint64(len(v.keys)), false), // count
+		llvm.ConstInt(ctx.Int8Type(), uint64(v.keySize), false),                        // keySize
+		llvm.ConstInt(ctx.Int8Type(), uint64(v.valueSize), false),                      // valueSize
+		llvm.ConstInt(ctx.Int8Type(), 0, false),                                        // bucketBits
+	})
+
+	v.hashmap = hashmap
+	return v.hashmap, nil
+}
+
+// putString does a map assign operation, assuming that the map is of type
+// map[string]T.
+func (v *mapValue) putString(mem *memoryView, stringBuf pointerValue, stringLen uint64, valuePtr pointerValue) error {
+	if !v.hashmap.IsNil() {
+		return errMapAlreadyCreated
+	}
+
+	value := mem.load(valuePtr, v.valueSize)
+	stringValue := mem.load(stringBuf, uint32(stringLen)).asRawValue(v.r)
+	if stringValue.hasPointer() {
+		panic("interp: string contains pointer")
+	}
+
+	// TODO: avoid duplicate keys
+	v.keys = append(v.keys, mapStringKey{stringBuf, stringLen, stringValue.buf})
+	v.values = append(v.values, value.asRawValue(v.r))
+	v.keyIsString = true
+
+	return nil
+}
+
+// putBinary does a map assign operation for binary data (e.g. [3]int etc). The
+// key must not contain pointer values.
+func (v *mapValue) putBinary(mem *memoryView, keyPtr, valuePtr pointerValue) error {
+	if !v.hashmap.IsNil() {
+		return errMapAlreadyCreated
+	}
+
+	key := mem.load(keyPtr, v.keySize)
+	value := mem.load(valuePtr, v.valueSize)
+
+	// Sanity checks.
+	if v.keySize != key.len(mem.r) || v.valueSize != value.len(mem.r) {
+		// This is a bug (not unhandled input), so panic.
+		panic("interp: key or value size mismatch")
+	}
+	if v.keyIsString {
+		panic("cannot put binary keys in string map")
+	}
+
+	// TODO: avoid duplicate keys
+	v.keys = append(v.keys, key.asRawValue(v.r))
+	v.values = append(v.values, value.asRawValue(v.r))
+
+	return nil
+}
+
+// Get FNV-1a hash of this string.
+//
+// https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function#FNV-1a_hash
+func (v *mapValue) hash(data []byte) uint32 {
+	var result uint32 = 2166136261 // FNV offset basis
+	for _, c := range data {
+		result ^= uint32(c)
+		result *= 16777619 // FNV prime
+	}
+	return result
+}
+
+// Get the topmost 8 bits of the hash, without using a special value (like 0).
+func (v *mapValue) topHash(hash uint32) uint8 {
+	tophash := uint8(hash >> 24)
+	if tophash < 1 {
+		// 0 means empty slot, so make it bigger.
+		tophash++
+	}
+	return tophash
+}
+
+func (v *mapValue) String() string {
+	return "<map keySize=" + strconv.Itoa(int(v.keySize)) + " valueSize=" + strconv.Itoa(int(v.valueSize)) + ">"
+}
+
 // rawValue is a raw memory buffer that can store either pointers or regular
 // data. This is the fallback data for everything that isn't clearly a
 // literalValue or pointerValue.
@@ -8,7 +8,6 @@ target triple = "x86_64--linux"
@main.exportedValue = global [1 x i16*] [i16* @main.exposedValue1]
@main.exposedValue1 = global i16 0
@main.exposedValue2 = global i16 0
-@main.insertedValue = global {i8, i32, {float, {i64, i16}}} zeroinitializer

 declare void @runtime.printint64(i64) unnamed_addr

@@ -66,19 +65,6 @@ entry:
  call void @modifyExternal(i32* bitcast (void ()* @willModifyGlobal to i32*))
  store i16 7, i16* @main.exposedValue2

-  ; Test switch statement.
-  %switch1 = call i64 @testSwitch(i64 1) ; 1 returns 6
-  %switch2 = call i64 @testSwitch(i64 9) ; 9 returns the default value -1
-  call void @runtime.printint64(i64 %switch1)
-  call void @runtime.printint64(i64 %switch2)
-
-  ; Test extractvalue/insertvalue with multiple operands.
-  %agg = call {i8, i32, {float, {i64, i16}}} @nestedStruct()
-  %elt = extractvalue {i8, i32, {float, {i64, i16}}} %agg, 2, 1, 0
-  call void @runtime.printint64(i64 %elt)
-  %agg2 = insertvalue {i8, i32, {float, {i64, i16}}} %agg, i64 5, 2, 1, 0
-  store {i8, i32, {float, {i64, i16}}} %agg2, {i8, i32, {float, {i64, i16}}}* @main.insertedValue
-
  ret void
 }

@@ -101,24 +87,3 @@ entry:
  store i16 8, i16* @main.exposedValue2
  ret void
 }
-
-define i64 @testSwitch(i64 %val) {
-entry:
-  ; Test switch statement.
-  switch i64 %val, label %otherwise [ i64 0, label %zero
-                                      i64 1, label %one
-                                      i64 2, label %two ]
-zero:
-  ret i64 5
-
-one:
-  ret i64 6
-
-two:
-  ret i64 7
-
-otherwise:
-  ret i64 -1
-}
-
-declare {i8, i32, {float, {i64, i16}}} @nestedStruct()
@@ -7,7 +7,6 @@ target triple = "x86_64--linux"
@main.exportedValue = global [1 x i16*] [i16* @main.exposedValue1]
@main.exposedValue1 = global i16 0
@main.exposedValue2 = local_unnamed_addr global i16 0
-@main.insertedValue = local_unnamed_addr global { i8, i32, { float, { i64, i16 } } } zeroinitializer

 declare void @runtime.printint64(i64) unnamed_addr

@@ -26,19 +25,6 @@ entry:
  store i16 5, i16* @main.exposedValue1
  call void @modifyExternal(i32* bitcast (void ()* @willModifyGlobal to i32*))
  store i16 7, i16* @main.exposedValue2
-  call void @runtime.printint64(i64 6)
-  call void @runtime.printint64(i64 -1)
-  %agg = call { i8, i32, { float, { i64, i16 } } } @nestedStruct()
-  %elt.agg = extractvalue { i8, i32, { float, { i64, i16 } } } %agg, 2
-  %elt.agg1 = extractvalue { float, { i64, i16 } } %elt.agg, 1
-  %elt = extractvalue { i64, i16 } %elt.agg1, 0
-  call void @runtime.printint64(i64 %elt)
-  %agg2.agg0 = extractvalue { i8, i32, { float, { i64, i16 } } } %agg, 2
-  %agg2.agg1 = extractvalue { float, { i64, i16 } } %agg2.agg0, 1
-  %agg2.insertvalue2 = insertvalue { i64, i16 } %agg2.agg1, i64 5, 0
-  %agg2.insertvalue1 = insertvalue { float, { i64, i16 } } %agg2.agg0, { i64, i16 } %agg2.insertvalue2, 1
-  %agg2.insertvalue0 = insertvalue { i8, i32, { float, { i64, i16 } } } %agg, { float, { i64, i16 } } %agg2.insertvalue1, 2
-  store { i8, i32, { float, { i64, i16 } } } %agg2.insertvalue0, { i8, i32, { float, { i64, i16 } } }* @main.insertedValue
  ret void
 }

@@ -58,26 +44,3 @@ entry:
  store i16 8, i16* @main.exposedValue2
  ret void
 }
-
-define i64 @testSwitch(i64 %val) local_unnamed_addr {
-entry:
-  switch i64 %val, label %otherwise [
-    i64 0, label %zero
-    i64 1, label %one
-    i64 2, label %two
-  ]
-
-zero:                                             ; preds = %entry
-  ret i64 5
-
-one:                                              ; preds = %entry
-  ret i64 6
-
-two:                                              ; preds = %entry
-  ret i64 7
-
-otherwise:                                        ; preds = %entry
-  ret i64 -1
-}
-
-declare { i8, i32, { float, { i64, i16 } } } @nestedStruct() local_unnamed_addr
@@ -6,7 +6,7 @@ target triple = "x86_64--linux"

@main.v1 = global i1 0
@"reflect/types.type:named:main.foo" = private constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:basic:int", i64 0, %runtime.interfaceMethodInfo* null }
-@"reflect/types.typeid:named:main.foo" = external constant i8
+@"reflect/types.type:named:main.foo$id" = external constant i8
@"reflect/types.type:basic:int" = external constant %runtime.typecodeID


@@ -21,7 +21,7 @@ entry:
 define internal void @main.init() unnamed_addr {
 entry:
  ; Test type asserts.
-  %typecode = call i1 @runtime.typeAssert(i64 ptrtoint (%runtime.typecodeID* @"reflect/types.type:named:main.foo" to i64), i8* @"reflect/types.typeid:named:main.foo", i8* undef, i8* null)
+  %typecode = call i1 @runtime.typeAssert(i64 ptrtoint (%runtime.typecodeID* @"reflect/types.type:named:main.foo" to i64), i8* @"reflect/types.type:named:main.foo$id", i8* undef, i8* null)
  store i1 %typecode, i1* @main.v1
  ret void
 }
@@ -0,0 +1,74 @@
+target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv6m-none-eabi"
+
+%runtime._string = type { i8*, i32 }
+%runtime.hashmap = type { %runtime.hashmap*, i8*, i32, i8, i8, i8 }
+
+@main.m = global %runtime.hashmap* null
+@main.binaryMap = global %runtime.hashmap* null
+@main.stringMap = global %runtime.hashmap* null
+@main.init.string = internal unnamed_addr constant [7 x i8] c"CONNECT"
+
+declare %runtime.hashmap* @runtime.hashmapMake(i8, i8, i32, i8* %context, i8* %parentHandle)
+declare void @runtime.hashmapBinarySet(%runtime.hashmap*, i8*, i8*, i8* %context, i8* %parentHandle)
+declare void @runtime.hashmapStringSet(%runtime.hashmap*, i8*, i32, i8*, i8* %context, i8* %parentHandle)
+declare void @llvm.lifetime.end.p0i8(i64, i8*)
+declare void @llvm.lifetime.start.p0i8(i64, i8*)
+
+define void @runtime.initAll() unnamed_addr {
+entry:
+  call void @main.init(i8* undef, i8* null)
+  ret void
+}
+
+define internal void @main.init(i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+; Test that hashmap optimizations generally work (even with lifetimes).
+  %hashmap.key = alloca i8
+  %hashmap.value = alloca %runtime._string
+  %0 = call %runtime.hashmap* @runtime.hashmapMake(i8 1, i8 8, i32 1, i8* undef, i8* null)
+  %hashmap.value.bitcast = bitcast %runtime._string* %hashmap.value to i8*
+  call void @llvm.lifetime.start.p0i8(i64 8, i8* %hashmap.value.bitcast)
+  store %runtime._string { i8* getelementptr inbounds ([7 x i8], [7 x i8]* @main.init.string, i32 0, i32 0), i32 7 }, %runtime._string* %hashmap.value
+  call void @llvm.lifetime.start.p0i8(i64 1, i8* %hashmap.key)
+  store i8 1, i8* %hashmap.key
+  call void @runtime.hashmapBinarySet(%runtime.hashmap* %0, i8* %hashmap.key, i8* %hashmap.value.bitcast, i8* undef, i8* null)
+  call void @llvm.lifetime.end.p0i8(i64 1, i8* %hashmap.key)
+  call void @llvm.lifetime.end.p0i8(i64 8, i8* %hashmap.value.bitcast)
+  store %runtime.hashmap* %0, %runtime.hashmap** @main.m
+
+  ; Other tests, that can be done in a separate function.
+  call void @main.testNonConstantBinarySet()
+  call void @main.testNonConstantStringSet()
+  ret void
+}
+
+; Test that a map loaded from a global can still be used for mapassign
+; operations (with binary keys).
+define internal void @main.testNonConstantBinarySet() {
+  %hashmap.key = alloca i8
+  %hashmap.value = alloca i8
+  ; Create hashmap from global.
+  %map.new = call %runtime.hashmap* @runtime.hashmapMake(i8 1, i8 1, i32 1, i8* undef, i8* null)
+  store %runtime.hashmap* %map.new, %runtime.hashmap** @main.binaryMap
+  %map = load %runtime.hashmap*, %runtime.hashmap** @main.binaryMap
+  ; Do the binary set to the newly loaded map.
+  store i8 1, i8* %hashmap.key
+  store i8 2, i8* %hashmap.value
+  call void @runtime.hashmapBinarySet(%runtime.hashmap* %map, i8* %hashmap.key, i8* %hashmap.value, i8* undef, i8* null)
+  ret void
+}
+
+; Test that a map loaded from a global can still be used for mapassign
+; operations (with string keys).
+define internal void @main.testNonConstantStringSet() {
+  %hashmap.value = alloca i8
+  ; Create hashmap from global.
+  %map.new = call %runtime.hashmap* @runtime.hashmapMake(i8 8, i8 1, i32 1, i8* undef, i8* null)
+  store %runtime.hashmap* %map.new, %runtime.hashmap** @main.stringMap
+  %map = load %runtime.hashmap*, %runtime.hashmap** @main.stringMap
+  ; Do the string set to the newly loaded map.
+  store i8 2, i8* %hashmap.value
+  call void @runtime.hashmapStringSet(%runtime.hashmap* %map, i8* getelementptr inbounds ([7 x i8], [7 x i8]* @main.init.string, i32 0, i32 0), i32 7, i8* %hashmap.value, i8* undef, i8* null)
+  ret void
+}
@@ -0,0 +1,20 @@
+target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv6m-none-eabi"
+
+%runtime.hashmap = type { %runtime.hashmap*, i8*, i32, i8, i8, i8 }
+
+@main.m = local_unnamed_addr global %runtime.hashmap* @"main$map"
+@main.binaryMap = local_unnamed_addr global %runtime.hashmap* @"main$map.1"
+@main.stringMap = local_unnamed_addr global %runtime.hashmap* @"main$map.3"
+@main.init.string = internal unnamed_addr constant [7 x i8] c"CONNECT"
+@"main$map" = internal global %runtime.hashmap { %runtime.hashmap* null, i8* getelementptr inbounds ({ [8 x i8], i8*, { i8, [7 x i8] }, { { [7 x i8]*, [4 x i8] }, [56 x i8] } }, { [8 x i8], i8*, { i8, [7 x i8] }, { { [7 x i8]*, [4 x i8] }, [56 x i8] } }* @"main$mapbucket", i32 0, i32 0, i32 0), i32 1, i8 1, i8 8, i8 0 }
+@"main$mapbucket" = internal unnamed_addr global { [8 x i8], i8*, { i8, [7 x i8] }, { { [7 x i8]*, [4 x i8] }, [56 x i8] } } { [8 x i8] c"\04\00\00\00\00\00\00\00", i8* null, { i8, [7 x i8] } { i8 1, [7 x i8] zeroinitializer }, { { [7 x i8]*, [4 x i8] }, [56 x i8] } { { [7 x i8]*, [4 x i8] } { [7 x i8]* @main.init.string, [4 x i8] c"\07\00\00\00" }, [56 x i8] zeroinitializer } }
+@"main$map.1" = internal global %runtime.hashmap { %runtime.hashmap* null, i8* getelementptr inbounds ({ [8 x i8], i8*, { i8, [7 x i8] }, { i8, [7 x i8] } }, { [8 x i8], i8*, { i8, [7 x i8] }, { i8, [7 x i8] } }* @"main$mapbucket.2", i32 0, i32 0, i32 0), i32 1, i8 1, i8 1, i8 0 }
+@"main$mapbucket.2" = internal unnamed_addr global { [8 x i8], i8*, { i8, [7 x i8] }, { i8, [7 x i8] } } { [8 x i8] c"\04\00\00\00\00\00\00\00", i8* null, { i8, [7 x i8] } { i8 1, [7 x i8] zeroinitializer }, { i8, [7 x i8] } { i8 2, [7 x i8] zeroinitializer } }
+@"main$map.3" = internal global %runtime.hashmap { %runtime.hashmap* null, i8* getelementptr inbounds ({ [8 x i8], i8*, { { [7 x i8]*, [4 x i8] }, [56 x i8] }, { i8, [7 x i8] } }, { [8 x i8], i8*, { { [7 x i8]*, [4 x i8] }, [56 x i8] }, { i8, [7 x i8] } }* @"main$mapbucket.4", i32 0, i32 0, i32 0), i32 1, i8 8, i8 1, i8 0 }
+@"main$mapbucket.4" = internal unnamed_addr global { [8 x i8], i8*, { { [7 x i8]*, [4 x i8] }, [56 x i8] }, { i8, [7 x i8] } } { [8 x i8] c"x\00\00\00\00\00\00\00", i8* null, { { [7 x i8]*, [4 x i8] }, [56 x i8] } { { [7 x i8]*, [4 x i8] } { [7 x i8]* @main.init.string, [4 x i8] c"\07\00\00\00" }, [56 x i8] zeroinitializer }, { i8, [7 x i8] } { i8 2, [7 x i8] zeroinitializer } }
+
+define void @runtime.initAll() unnamed_addr {
+entry:
+  ret void
+}
@@ -1,31 +0,0 @@
-target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
-target triple = "x86_64--linux"
-
-@main.phiNodesResultA = global i8 0
-@main.phiNodesResultB = global i8 0
-
-define void @runtime.initAll() {
-  call void @main.init()
-  ret void
-}
-
-; PHI nodes always use the value from the previous block, even in a loop. This
-; means that the loop below should swap the values %a and %b on each iteration.
-; Previously there was a bug which resulted in %b getting the value 3 on the
-; second iteration while it should have gotten 1 (from the first iteration of
-; %for.loop).
-define internal void @main.init() {
-entry:
-  br label %for.loop
-
-for.loop:
-  %a = phi i8 [ 1, %entry ], [ %b, %for.loop ]
-  %b = phi i8 [ 3, %entry ], [ %a, %for.loop ]
-  %icmp = icmp eq i8 %a, 3
-  br i1 %icmp, label %for.done, label %for.loop
-
-for.done:
-  store i8 %a, i8* @main.phiNodesResultA
-  store i8 %b, i8* @main.phiNodesResultB
-  ret void
-}
@@ -1,9 +0,0 @@
-target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
-target triple = "x86_64--linux"
-
-@main.phiNodesResultA = local_unnamed_addr global i8 3
-@main.phiNodesResultB = local_unnamed_addr global i8 1
-
-define void @runtime.initAll() local_unnamed_addr {
-  ret void
-}
@@ -23,13 +23,3 @@ type Error struct {
 func (e Error) Error() string {
 	return e.Err.Error()
 }
-
-// Error returned when loading a *Program for a test binary but no test files
-// are present.
-type NoTestFilesError struct {
-	ImportPath string
-}
-
-func (e NoTestFilesError) Error() string {
-	return "no test files"
-}
@@ -210,12 +210,6 @@ func Load(config *compileopts.Config, inputPkgs []string, clangHeaders string, t
 		p.Packages[pkg.ImportPath] = pkg
 	}

-	if config.TestConfig.CompileTestBinary && !strings.HasSuffix(p.sorted[len(p.sorted)-1].ImportPath, ".test") {
-		// Trying to compile a test binary but there are no test files in this
-		// package.
-		return p, NoTestFilesError{p.sorted[len(p.sorted)-1].ImportPath}
-	}
-
 	return p, nil
 }

@@ -13,13 +13,11 @@ import (
 	"os/exec"
 	"os/signal"
 	"path/filepath"
-	"regexp"
 	"runtime"
 	"strings"
 	"sync/atomic"
 	"time"

-	"github.com/google/shlex"
 	"github.com/mattn/go-colorable"
 	"github.com/tinygo-org/tinygo/builder"
 	"github.com/tinygo-org/tinygo/compileopts"
@@ -30,7 +28,6 @@ import (
 	"tinygo.org/x/go-llvm"

 	"go.bug.st/serial"
-	"go.bug.st/serial/enumerator"
 )

 var (
@@ -136,17 +133,15 @@ func Build(pkgName, outpath string, options *compileopts.Options) error {
 	})
 }

-// Test runs the tests in the given package. Returns whether the test passed and
-// possibly an error if the test failed to run.
-func Test(pkgName string, options *compileopts.Options, testCompileOnly bool, outpath string) (bool, error) {
+// Test runs the tests in the given package.
+func Test(pkgName string, options *compileopts.Options, testCompileOnly bool, outpath string) error {
 	options.TestConfig.CompileTestBinary = true
 	config, err := builder.NewConfig(options)
 	if err != nil {
-		return false, err
+		return err
 	}

-	var passed bool
-	err = builder.Build(pkgName, outpath, config, func(result builder.BuildResult) error {
+	return builder.Build(pkgName, outpath, config, func(result builder.BuildResult) error {
 		if testCompileOnly || outpath != "" {
 			// Write test binary to the specified file name.
 			if outpath == "" {
@@ -160,78 +155,48 @@ func Test(pkgName string, options *compileopts.Options, testCompileOnly bool, ou
 			// Do not run the test.
 			return nil
 		}
-
-		// Run the test.
-		start := time.Now()
-		var err error
-		passed, err = runPackageTest(config, result)
-		if err != nil {
-			return err
-		}
-		duration := time.Since(start)
-
-		// Print the result.
-		importPath := strings.TrimSuffix(result.ImportPath, ".test")
-		if passed {
-			fmt.Printf("ok  \t%s\t%.3fs\n", importPath, duration.Seconds())
+		if len(config.Target.Emulator) == 0 {
+			// Run directly.
+			cmd := executeCommand(config.Options, result.Binary)
+			cmd.Stdout = os.Stdout
+			cmd.Stderr = os.Stderr
+			cmd.Dir = result.MainDir
+			err := cmd.Run()
+			if err != nil {
+				// Propagate the exit code
+				if err, ok := err.(*exec.ExitError); ok {
+					os.Exit(err.ExitCode())
+				}
+				return &commandError{"failed to run compiled binary", result.Binary, err}
+			}
+			return nil
 		} else {
-			fmt.Printf("FAIL\t%s\t%.3fs\n", importPath, duration.Seconds())
+			// Run in an emulator.
+			args := append(config.Target.Emulator[1:], result.Binary)
+			cmd := executeCommand(config.Options, config.Target.Emulator[0], args...)
+			buf := &bytes.Buffer{}
+			w := io.MultiWriter(os.Stdout, buf)
+			cmd.Stdout = w
+			cmd.Stderr = os.Stderr
+			err := cmd.Run()
+			if err != nil {
+				if err, ok := err.(*exec.ExitError); !ok || !err.Exited() {
+					// Workaround for QEMU which always exits with an error.
+					return &commandError{"failed to run emulator with", result.Binary, err}
+				}
+			}
+			testOutput := string(buf.Bytes())
+			if testOutput == "PASS\n" || strings.HasSuffix(testOutput, "\nPASS\n") {
+				// Test passed.
+				return nil
+			} else {
+				// Test failed, either by ending with the word "FAIL" or with a
+				// panic of some sort.
+				os.Exit(1)
+				return nil // unreachable
+			}
 		}
-		return nil
 	})
-	if err, ok := err.(loader.NoTestFilesError); ok {
-		fmt.Printf("?   \t%s\t[no test files]\n", err.ImportPath)
-		// Pretend the test passed - it at least didn't fail.
-		return true, nil
-	}
-	return passed, err
-}
-
-// runPackageTest runs a test binary that was previously built. The return
-// values are whether the test passed and any errors encountered while trying to
-// run the binary.
-func runPackageTest(config *compileopts.Config, result builder.BuildResult) (bool, error) {
-	if len(config.Target.Emulator) == 0 {
-		// Run directly.
-		cmd := executeCommand(config.Options, result.Binary)
-		cmd.Stdout = os.Stdout
-		cmd.Stderr = os.Stderr
-		cmd.Dir = result.MainDir
-		err := cmd.Run()
-		if err != nil {
-			if _, ok := err.(*exec.ExitError); ok {
-				// Binary exited with a non-zero exit code, which means the test
-				// failed.
-				return false, nil
-			}
-			return false, &commandError{"failed to run compiled binary", result.Binary, err}
-		}
-		return true, nil
-	} else {
-		// Run in an emulator.
-		args := append(config.Target.Emulator[1:], result.Binary)
-		cmd := executeCommand(config.Options, config.Target.Emulator[0], args...)
-		buf := &bytes.Buffer{}
-		w := io.MultiWriter(os.Stdout, buf)
-		cmd.Stdout = w
-		cmd.Stderr = os.Stderr
-		err := cmd.Run()
-		if err != nil {
-			if err, ok := err.(*exec.ExitError); !ok || !err.Exited() {
-				// Workaround for QEMU which always exits with an error.
-				return false, &commandError{"failed to run emulator with", result.Binary, err}
-			}
-		}
-		testOutput := string(buf.Bytes())
-		if testOutput == "PASS\n" || strings.HasSuffix(testOutput, "\nPASS\n") {
-			// Test passed.
-			return true, nil
-		} else {
-			// Test failed, either by ending with the word "FAIL" or with a
-			// panic of some sort.
-			return false, nil
-		}
-	}
 }

 // Flash builds and flashes the built binary to the given serial port.
@@ -275,12 +240,15 @@ func Flash(pkgName, port string, options *compileopts.Options) error {
 	return builder.Build(pkgName, fileExt, config, func(result builder.BuildResult) error {
 		// do we need port reset to put MCU into bootloader mode?
 		if config.Target.PortReset == "true" && flashMethod != "openocd" {
-			port, err := getDefaultPort(strings.FieldsFunc(port, func(c rune) bool { return c == ',' }))
-			if err != nil {
-				return err
+			if port == "" {
+				var err error
+				port, err = getDefaultPort()
+				if err != nil {
+					return err
+				}
 			}

-			err = touchSerialPortAt1200bps(port)
+			err := touchSerialPortAt1200bps(port)
 			if err != nil {
 				return &commandError{"failed to reset port", result.Binary, err}
 			}
@@ -296,9 +264,9 @@ func Flash(pkgName, port string, options *compileopts.Options) error {
 			fileToken := "{" + fileExt[1:] + "}"
 			flashCmd = strings.ReplaceAll(flashCmd, fileToken, result.Binary)

-			if strings.Contains(flashCmd, "{port}") {
+			if port == "" && strings.Contains(flashCmd, "{port}") {
 				var err error
-				port, err = getDefaultPort(strings.FieldsFunc(port, func(c rune) bool { return c == ',' }))
+				port, err = getDefaultPort()
 				if err != nil {
 					return err
 				}
@@ -697,66 +665,41 @@ func windowsFindUSBDrive(volume string, options *compileopts.Options) (string, e
 }

 // getDefaultPort returns the default serial port depending on the operating system.
-func getDefaultPort(portCandidates []string) (port string, err error) {
-	if len(portCandidates) == 1 {
-		return portCandidates[0], nil
-	}
-
-	var ports []string
+func getDefaultPort() (port string, err error) {
+	var portPath string
 	switch runtime.GOOS {
+	case "darwin":
+		portPath = "/dev/cu.usb*"
+	case "linux":
+		portPath = "/dev/ttyACM*"
 	case "freebsd":
-		ports, err = filepath.Glob("/dev/cuaU*")
-	case "darwin", "linux", "windows":
-		var portsList []*enumerator.PortDetails
-		portsList, err = enumerator.GetDetailedPortsList()
+		portPath = "/dev/cuaU*"
+	case "windows":
+		ports, err := serial.GetPortsList()
 		if err != nil {
 			return "", err
 		}

-		for _, p := range portsList {
-			ports = append(ports, p.Name)
+		if len(ports) == 0 {
+			return "", errors.New("no serial ports available")
+		} else if len(ports) > 1 {
+			return "", errors.New("multiple serial ports available - use -port flag")
 		}

-		if ports == nil || len(ports) == 0 {
-			// fallback
-			switch runtime.GOOS {
-			case "darwin":
-				ports, err = filepath.Glob("/dev/cu.usb*")
-			case "linux":
-				ports, err = filepath.Glob("/dev/ttyACM*")
-			case "windows":
-				ports, err = serial.GetPortsList()
-			}
-		}
+		return ports[0], nil
 	default:
 		return "", errors.New("unable to search for a default USB device to be flashed on this OS")
 	}

+	d, err := filepath.Glob(portPath)
 	if err != nil {
 		return "", err
-	} else if ports == nil {
+	}
+	if d == nil {
 		return "", errors.New("unable to locate a serial port")
-	} else if len(ports) == 0 {
-		return "", errors.New("no serial ports available")
 	}

-	if len(portCandidates) == 0 {
-		if len(ports) == 1 {
-			return ports[0], nil
-		} else {
-			return "", errors.New("multiple serial ports available - use -port flag, available ports are " + strings.Join(ports, ", "))
-		}
-	}
-
-	for _, ps := range portCandidates {
-		for _, p := range ports {
-			if p == ps {
-				return p, nil
-			}
-		}
-	}
-
-	return "", errors.New("port you specified '" + strings.Join(portCandidates, ",") + "' does not exist, available ports are " + strings.Join(ports, ", "))
+	return d[0], nil
 }

 func usage() {
@@ -869,52 +812,6 @@ func handleCompilerError(err error) {
 	}
 }

-// This is a special type for the -X flag to parse the pkgpath.Var=stringVal
-// format. It has to be a special type to allow multiple variables to be defined
-// this way.
-type globalValuesFlag map[string]map[string]string
-
-func (m globalValuesFlag) String() string {
-	return "pkgpath.Var=value"
-}
-
-func (m globalValuesFlag) Set(value string) error {
-	equalsIndex := strings.IndexByte(value, '=')
-	if equalsIndex < 0 {
-		return errors.New("expected format pkgpath.Var=value")
-	}
-	pathAndName := value[:equalsIndex]
-	pointIndex := strings.LastIndexByte(pathAndName, '.')
-	if pointIndex < 0 {
-		return errors.New("expected format pkgpath.Var=value")
-	}
-	path := pathAndName[:pointIndex]
-	name := pathAndName[pointIndex+1:]
-	stringValue := value[equalsIndex+1:]
-	if m[path] == nil {
-		m[path] = make(map[string]string)
-	}
-	m[path][name] = stringValue
-	return nil
-}
-
-// parseGoLinkFlag parses the -ldflags parameter. Its primary purpose right now
-// is the -X flag, for setting the value of global string variables.
-func parseGoLinkFlag(flagsString string) (map[string]map[string]string, error) {
-	set := flag.NewFlagSet("link", flag.ExitOnError)
-	globalVarValues := make(globalValuesFlag)
-	set.Var(globalVarValues, "X", "Set the value of the string variable to the given value.")
-	flags, err := shlex.Split(flagsString)
-	if err != nil {
-		return nil, err
-	}
-	err = set.Parse(flags)
-	if err != nil {
-		return nil, err
-	}
-	return map[string]map[string]string(globalVarValues), nil
-}
-
 func main() {
 	if len(os.Args) < 2 {
 		fmt.Fprintln(os.Stderr, "No command-line arguments supplied.")
@@ -934,16 +831,14 @@ func main() {
 	target := flag.String("target", "", "LLVM target | .json file with TargetSpec")
 	printSize := flag.String("size", "", "print sizes (none, short, full)")
 	printStacks := flag.Bool("print-stacks", false, "print stack sizes of goroutines")
-	printAllocsString := flag.String("print-allocs", "", "regular expression of functions for which heap allocations should be printed")
 	printCommands := flag.Bool("x", false, "Print commands")
 	nodebug := flag.Bool("no-debug", false, "disable DWARF debug symbol generation")
-	ocdCommandsString := flag.String("ocd-commands", "", "OpenOCD commands, overriding target spec (can specify multiple separated by commas)")
 	ocdOutput := flag.Bool("ocd-output", false, "print OCD daemon output during debug")
-	port := flag.String("port", "", "flash port (can specify multiple candidates separated by commas)")
+	port := flag.String("port", "", "flash port")
 	programmer := flag.String("programmer", "", "which hardware programmer to use")
-	ldflags := flag.String("ldflags", "", "Go link tool compatible ldflags")
+	cFlags := flag.String("cflags", "", "additional cflags for compiler")
+	ldFlags := flag.String("ldflags", "", "additional ldflags for linker")
 	wasmAbi := flag.String("wasm-abi", "", "WebAssembly ABI conventions: js (no i64 params) or generic")
-	llvmFeatures := flag.String("llvm-features", "", "comma separated LLVM features to enable")

 	var flagJSON, flagDeps *bool
 	if command == "help" || command == "list" {
@@ -972,51 +867,35 @@ func main() {
 	}

 	flag.CommandLine.Parse(os.Args[2:])
-	globalVarValues, err := parseGoLinkFlag(*ldflags)
-	if err != nil {
-		fmt.Fprintln(os.Stderr, err)
-		os.Exit(1)
-	}
-
-	var printAllocs *regexp.Regexp
-	if *printAllocsString != "" {
-		printAllocs, err = regexp.Compile(*printAllocsString)
-		if err != nil {
-			fmt.Fprintln(os.Stderr, err)
-			os.Exit(1)
-		}
-	}
-
-	var ocdCommands []string
-	if *ocdCommandsString != "" {
-		ocdCommands = strings.Split(*ocdCommandsString, ",")
-	}
-
 	options := &compileopts.Options{
-		Target:          *target,
-		Opt:             *opt,
-		GC:              *gc,
-		PanicStrategy:   *panicStrategy,
-		Scheduler:       *scheduler,
-		PrintIR:         *printIR,
-		DumpSSA:         *dumpSSA,
-		VerifyIR:        *verifyIR,
-		Debug:           !*nodebug,
-		PrintSizes:      *printSize,
-		PrintStacks:     *printStacks,
-		PrintAllocs:     printAllocs,
-		PrintCommands:   *printCommands,
-		Tags:            *tags,
-		GlobalValues:    globalVarValues,
-		WasmAbi:         *wasmAbi,
-		Programmer:      *programmer,
-		OpenOCDCommands: ocdCommands,
-		LLVMFeatures:    *llvmFeatures,
+		Target:        *target,
+		Opt:           *opt,
+		GC:            *gc,
+		PanicStrategy: *panicStrategy,
+		Scheduler:     *scheduler,
+		PrintIR:       *printIR,
+		DumpSSA:       *dumpSSA,
+		VerifyIR:      *verifyIR,
+		Debug:         !*nodebug,
+		PrintSizes:    *printSize,
+		PrintStacks:   *printStacks,
+		PrintCommands: *printCommands,
+		Tags:          *tags,
+		WasmAbi:       *wasmAbi,
+		Programmer:    *programmer,
+	}
+
+	if *cFlags != "" {
+		options.CFlags = strings.Split(*cFlags, " ")
+	}
+
+	if *ldFlags != "" {
+		options.LDFlags = strings.Split(*ldFlags, " ")
 	}

 	os.Setenv("CC", "clang -target="+*target)

-	err = options.Verify()
+	err := options.Verify()
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err.Error())
 		usage()
@@ -1104,26 +983,16 @@ func main() {
 		err := Run(pkgName, options)
 		handleCompilerError(err)
 	case "test":
-		var pkgNames []string
-		for i := 0; i < flag.NArg(); i++ {
-			pkgNames = append(pkgNames, filepath.ToSlash(flag.Arg(i)))
-		}
-		if len(pkgNames) == 0 {
-			pkgNames = []string{"."}
-		}
-		allTestsPassed := true
-		for _, pkgName := range pkgNames {
-			// TODO: parallelize building the test binaries
-			passed, err := Test(pkgName, options, *testCompileOnlyFlag, outpath)
-			handleCompilerError(err)
-			if !passed {
-				allTestsPassed = false
-			}
-		}
-		if !allTestsPassed {
-			fmt.Println("FAIL")
+		pkgName := "."
+		if flag.NArg() == 1 {
+			pkgName = filepath.ToSlash(flag.Arg(0))
+		} else if flag.NArg() > 1 {
+			fmt.Fprintln(os.Stderr, "test only accepts a single positional argument: package name, but multiple were specified")
+			usage()
 			os.Exit(1)
 		}
+		err := Test(pkgName, options, *testCompileOnlyFlag, outpath)
+		handleCompilerError(err)
 	case "targets":
 		dir := filepath.Join(goenv.Get("TINYGOROOT"), "targets")
 		entries, err := ioutil.ReadDir(dir)
@@ -13,8 +13,8 @@ import (
 	"os/exec"
 	"path/filepath"
 	"runtime"
+	"sort"
 	"strings"
-	"sync"
 	"testing"
 	"time"

@@ -28,43 +28,41 @@ const TESTDATA = "testdata"
 var testTarget = flag.String("target", "", "override test target")

 func TestCompiler(t *testing.T) {
-	tests := []string{
-		"alias.go",
-		"atomic.go",
-		"binop.go",
-		"calls.go",
-		"cgo/",
-		"channel.go",
-		"coroutines.go",
-		"float.go",
-		"gc.go",
-		"init.go",
-		"init_multi.go",
-		"interface.go",
-		"json.go",
-		"map.go",
-		"math.go",
-		"print.go",
-		"reflect.go",
-		"slice.go",
-		"sort.go",
-		"stdlib.go",
-		"string.go",
-		"structs.go",
-		"zeroalloc.go",
+	matches, err := filepath.Glob(filepath.Join(TESTDATA, "*.go"))
+	if err != nil {
+		t.Fatal("could not read test files:", err)
 	}

+	dirMatches, err := filepath.Glob(filepath.Join(TESTDATA, "*", "main.go"))
+	if err != nil {
+		t.Fatal("could not read test packages:", err)
+	}
+	if len(matches) == 0 || len(dirMatches) == 0 {
+		t.Fatal("no test files found")
+	}
+	for _, m := range dirMatches {
+		matches = append(matches, filepath.Dir(m)+string(filepath.Separator))
+	}
+
+	sort.Strings(matches)
+
 	if *testTarget != "" {
 		// This makes it possible to run one specific test (instead of all),
 		// which is especially useful to quickly check whether some changes
 		// affect a particular target architecture.
-		runPlatTests(*testTarget, tests, t)
+		runPlatTests(*testTarget, matches, t)
 		return
 	}

 	if runtime.GOOS != "windows" {
 		t.Run("Host", func(t *testing.T) {
-			runPlatTests("", tests, t)
+			runPlatTests("", matches, t)
+			if runtime.GOOS == "darwin" {
+				runTest("testdata/libc/filesystem.go", "", t,
+					nil, nil)
+				runTest("testdata/libc/env.go", "", t,
+					[]string{"ENV1=VALUE1", "ENV2=VALUE2"}, nil)
+			}
 		})
 	}

@@ -73,26 +71,26 @@ func TestCompiler(t *testing.T) {
 	}

 	t.Run("EmulatedCortexM3", func(t *testing.T) {
-		runPlatTests("cortex-m-qemu", tests, t)
+		runPlatTests("cortex-m-qemu", matches, t)
 	})

 	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" {
 		// Note: running only on Windows and macOS because Linux (as of 2020)
 		// usually has an outdated QEMU version that doesn't support RISC-V yet.
 		t.Run("EmulatedRISCV", func(t *testing.T) {
-			runPlatTests("riscv-qemu", tests, t)
+			runPlatTests("riscv-qemu", matches, t)
 		})
 	}

 	if runtime.GOOS == "linux" {
 		t.Run("X86Linux", func(t *testing.T) {
-			runPlatTests("i386--linux-gnu", tests, t)
+			runPlatTests("i386--linux-gnu", matches, t)
 		})
 		t.Run("ARMLinux", func(t *testing.T) {
-			runPlatTests("arm--linux-gnueabihf", tests, t)
+			runPlatTests("arm--linux-gnueabihf", matches, t)
 		})
 		t.Run("ARM64Linux", func(t *testing.T) {
-			runPlatTests("aarch64--linux-gnu", tests, t)
+			runPlatTests("aarch64--linux-gnu", matches, t)
 		})
 		goVersion, err := goenv.GorootVersionString(goenv.Get("GOROOT"))
 		if err != nil {
@@ -105,110 +103,35 @@ func TestCompiler(t *testing.T) {
 			// below that are also not supported but still seem to pass, so
 			// include them in the tests for now.
 			t.Run("WebAssembly", func(t *testing.T) {
-				runPlatTests("wasm", tests, t)
+				runPlatTests("wasm", matches, t)
 			})
 		}

 		t.Run("WASI", func(t *testing.T) {
-			runPlatTests("wasi", tests, t)
+			runPlatTests("wasi", matches, t)
+			runTest("testdata/libc/env.go", "wasi", t,
+				[]string{"--env", "ENV1=VALUE1", "--env", "ENV2=VALUE2"}, nil)
+			runTest("testdata/libc/filesystem.go", "wasi", t, nil, []string{"--dir=."})
 		})
 	}
-
-	// Test a few build options.
-	t.Run("build-options", func(t *testing.T) {
-		if runtime.GOOS == "windows" {
-			// These tests assume a host that is supported by TinyGo.
-			t.Skip("can't test build options on Windows")
-		}
-		t.Parallel()
-
-		// Test with few optimizations enabled (no inlining, etc).
-		t.Run("opt=1", func(t *testing.T) {
-			t.Parallel()
-			runTestWithConfig("stdlib.go", "", t, &compileopts.Options{
-				Opt: "1",
-			}, nil, nil)
-		})
-
-		// Test with only the bare minimum of optimizations enabled.
-		// TODO: fix this for stdlib.go, which currently fails.
-		t.Run("opt=0", func(t *testing.T) {
-			t.Parallel()
-			runTestWithConfig("print.go", "", t, &compileopts.Options{
-				Opt: "0",
-			}, nil, nil)
-		})
-
-		t.Run("ldflags", func(t *testing.T) {
-			t.Parallel()
-			runTestWithConfig("ldflags.go", "", t, &compileopts.Options{
-				Opt: "z",
-				GlobalValues: map[string]map[string]string{
-					"main": {
-						"someGlobal": "foobar",
-					},
-				},
-			}, nil, nil)
-		})
-	})
 }

-func runPlatTests(target string, tests []string, t *testing.T) {
+func runPlatTests(target string, matches []string, t *testing.T) {
 	t.Parallel()

-	for _, name := range tests {
-		name := name // redefine to avoid race condition
-		t.Run(name, func(t *testing.T) {
+	for _, path := range matches {
+		path := path // redefine to avoid race condition
+		t.Run(filepath.Base(path), func(t *testing.T) {
 			t.Parallel()
-			runTest(name, target, t, nil, nil)
-		})
-	}
-	if target == "wasi" || target == "" {
-		t.Run("filesystem.go", func(t *testing.T) {
-			t.Parallel()
-			runTest("filesystem.go", target, t, nil, nil)
-		})
-		t.Run("env.go", func(t *testing.T) {
-			t.Parallel()
-			runTest("env.go", target, t, []string{"first", "second"}, []string{"ENV1=VALUE1", "ENV2=VALUE2"})
+			runTest(path, target, t, nil, nil)
 		})
 	}
 }

-// Due to some problems with LLD, we cannot run links in parallel, or in parallel with compiles.
-// Therefore, we put a lock around builds and run everything else in parallel.
-var buildLock sync.Mutex
-
-// runBuild is a thread-safe wrapper around Build.
-func runBuild(src, out string, opts *compileopts.Options) error {
-	buildLock.Lock()
-	defer buildLock.Unlock()
-
-	return Build(src, out, opts)
-}
-
-func runTest(name, target string, t *testing.T, cmdArgs, environmentVars []string) {
-	options := &compileopts.Options{
-		Target:     target,
-		Opt:        "z",
-		PrintIR:    false,
-		DumpSSA:    false,
-		VerifyIR:   true,
-		Debug:      true,
-		PrintSizes: "",
-		WasmAbi:    "",
-	}
-	runTestWithConfig(name, target, t, options, cmdArgs, environmentVars)
-}
-
-func runTestWithConfig(name, target string, t *testing.T, options *compileopts.Options, cmdArgs, environmentVars []string) {
-	// Get the expected output for this test.
-	// Note: not using filepath.Join as it strips the path separator at the end
-	// of the path.
-	path := TESTDATA + "/" + name
+func runTest(path, target string, t *testing.T, environmentVars []string, additionalArgs []string) {
 	// Get the expected output for this test.
 	txtpath := path[:len(path)-3] + ".txt"
-	if path[len(path)-1] == '/' {
+	if path[len(path)-1] == os.PathSeparator {
 		txtpath = path + "out.txt"
 	}
 	expected, err := ioutil.ReadFile(txtpath)
@@ -229,8 +152,19 @@ func runTestWithConfig(name, target string, t *testing.T, options *compileopts.O
 	}()

 	// Build the test binary.
+	config := &compileopts.Options{
+		Target:     target,
+		Opt:        "z",
+		PrintIR:    false,
+		DumpSSA:    false,
+		VerifyIR:   true,
+		Debug:      true,
+		PrintSizes: "",
+		WasmAbi:    "",
+	}
+
 	binary := filepath.Join(tmpdir, "test")
-	err = runBuild("./"+path, binary, options)
+	err = Build("./"+path, binary, config)
 	if err != nil {
 		printCompilerError(t.Log, err)
 		t.Fail()
@@ -244,7 +178,6 @@ func runTestWithConfig(name, target string, t *testing.T, options *compileopts.O
 	if target == "" {
 		cmd = exec.Command(binary)
 		cmd.Env = append(cmd.Env, environmentVars...)
-		cmd.Args = append(cmd.Args, cmdArgs...)
 	} else {
 		spec, err := compileopts.LoadTarget(target)
 		if err != nil {
@@ -254,16 +187,13 @@ func runTestWithConfig(name, target string, t *testing.T, options *compileopts.O
 			cmd = exec.Command(binary)
 		} else {
 			args := append(spec.Emulator[1:], binary)
-			cmd = exec.Command(spec.Emulator[0], args...)
+			cmd = exec.Command(spec.Emulator[0], append(args, additionalArgs...)...)
 		}

 		if len(spec.Emulator) != 0 && spec.Emulator[0] == "wasmtime" {
-			// Allow reading from the current directory.
-			cmd.Args = append(cmd.Args, "--dir=.")
 			for _, v := range environmentVars {
 				cmd.Args = append(cmd.Args, "--env", v)
 			}
-			cmd.Args = append(cmd.Args, cmdArgs...)
 		} else {
 			cmd.Env = append(cmd.Env, environmentVars...)
 		}
@@ -26,21 +26,12 @@ type SCB_Type struct {
 	SHPR2 volatile.Register32 // 0xD1C: System Handler Priority Register 2
 	SHPR3 volatile.Register32 // 0xD20: System Handler Priority Register 3
 	// the following are only applicable for Cortex-M3/M33/M4/M7
-	SHCSR volatile.Register32    // 0xD24: System Handler Control and State Register
-	CFSR  volatile.Register32    // 0xD28: Configurable Fault Status Register
-	HFSR  volatile.Register32    // 0xD2C: HardFault Status Register
-	DFSR  volatile.Register32    // 0xD30: Debug Fault Status Register
-	MMFAR volatile.Register32    // 0xD34: MemManage Fault Address Register
-	BFAR  volatile.Register32    // 0xD38: BusFault Address Register
-	AFSR  volatile.Register32    // 0xD3C: Auxiliary Fault Status Register
-	PFR   [2]volatile.Register32 // 0xD40: Processor Feature Register
-	DFR   volatile.Register32    // 0xD48: Debug Feature Register
-	ADR   volatile.Register32    // 0xD4C: Auxiliary Feature Register
-	MMFR  [4]volatile.Register32 // 0xD50: Memory Model Feature Register
-	ISAR  [5]volatile.Register32 // 0xD60: Instruction Set Attributes Register
-	_     [5]uint32              // reserved
-	CPACR volatile.Register32    // 0xD88: Coprocessor Access Control Register
-
+	SHCSR volatile.Register32 // 0xD24: System Handler Control and State Register
+	CFSR  volatile.Register32 // 0xD28: Configurable Fault Status Register
+	HFSR  volatile.Register32 // 0xD2C: HardFault Status Register
+	DFSR  volatile.Register32 // 0xD30: Debug Fault Status Register
+	MMFAR volatile.Register32 // 0xD34: MemManage Fault Address Register
+	BFAR  volatile.Register32 // 0xD38: BusFault Address Register
 }

 var SCB = (*SCB_Type)(unsafe.Pointer(uintptr(SCB_BASE)))
@@ -1,71 +0,0 @@
-// Hand created file. DO NOT DELETE.
-// atsamd51x bitfield definitions that are not auto-generated by gen-device-svd.go
-
-// +build sam,atsame5x
-
-// These are the supported pchctrl function numberings on the atsamd51x
-// See http://ww1.microchip.com/downloads/en/DeviceDoc/SAM_D5xE5x_Family_Data_Sheet_DS60001507F.pdf
-// table 14-9
-
-package sam
-
-const (
-	PCHCTRL_GCLK_OSCCTRL_DFLL48     = 0 // DFLL48 input clock source
-	PCHCTRL_GCLK_OSCCTRL_FDPLL0     = 1 // Reference clock for FDPLL0
-	PCHCTRL_GCLK_OSCCTRL_FDPLL1     = 2 // Reference clock for FDPLL1
-	PCHCTRL_GCLK_OSCCTRL_FDPLL0_32K = 3 // FDPLL0 = 3 // 32KHz clock for internal lock timer
-	PCHCTRL_GCLK_OSCCTRL_FDPLL1_32K = 3 // FDPLL1 = 3 // 32KHz clock for internal lock timer
-	PCHCTRL_GCLK_SDHC0_SLOW         = 3 // SDHC0 = 3 // Slow
-	PCHCTRL_GCLK_SDHC1_SLOW         = 3 // SDHC1 = 3 // Slow
-	PCHCTRL_GCLK_SERCOMX_SLOW       = 3 // GCLK_SERCOM[0..7]_SLOW = 3
-	PCHCTRL_GCLK_EIC                = 4
-	PCHCTRL_GCLK_FREQM_MSR          = 5 // FREQM Measure
-	PCHCTRL_GCLK_FREQM_REF          = 6 // FREQM Reference
-	PCHCTRL_GCLK_SERCOM0_CORE       = 7 // SERCOM0 Core
-	PCHCTRL_GCLK_SERCOM1_CORE       = 8 // SERCOM1 Core
-	PCHCTRL_GCLK_TC0                = 9
-	PCHCTRL_GCLK_TC1                = 9  // TC0, TC1
-	PCHCTRL_GCLK_USB                = 10 // USB
-	PCHCTRL_GCLK_EVSYS0             = 11
-	PCHCTRL_GCLK_EVSYS1             = 12
-	PCHCTRL_GCLK_EVSYS2             = 13
-	PCHCTRL_GCLK_EVSYS3             = 14
-	PCHCTRL_GCLK_EVSYS4             = 15
-	PCHCTRL_GCLK_EVSYS5             = 16
-	PCHCTRL_GCLK_EVSYS6             = 17
-	PCHCTRL_GCLK_EVSYS7             = 18
-	PCHCTRL_GCLK_EVSYS8             = 19
-	PCHCTRL_GCLK_EVSYS9             = 20
-	PCHCTRL_GCLK_EVSYS10            = 21
-	PCHCTRL_GCLK_EVSYS11            = 22
-	PCHCTRL_GCLK_SERCOM2_CORE       = 23 // SERCOM2 Core
-	PCHCTRL_GCLK_SERCOM3_CORE       = 24 // SERCOM3 Core
-	PCHCTRL_GCLK_TCC0               = 25
-	PCHCTRL_GCLK_TCC1               = 25 // TCC0, TCC1
-	PCHCTRL_GCLK_TC2                = 26
-	PCHCTRL_GCLK_TC3                = 26 // TC2, TC3
-	PCHCTRL_GCLK_CAN0               = 27 // CAN0
-	PCHCTRL_GCLK_CAN1               = 28 // CAN1
-	PCHCTRL_GCLK_TCC2               = 29
-	PCHCTRL_GCLK_TCC3               = 29 // TCC2, TCC3
-	PCHCTRL_GCLK_TC4                = 30
-	PCHCTRL_GCLK_TC5                = 30 // TC4, TC5
-	PCHCTRL_GCLK_PDEC               = 31 // PDEC
-	PCHCTRL_GCLK_AC                 = 32 // AC
-	PCHCTRL_GCLK_CCL                = 33 // CCL
-	PCHCTRL_GCLK_SERCOM4_CORE       = 34 // SERCOM4 Core
-	PCHCTRL_GCLK_SERCOM5_CORE       = 35 // SERCOM5 Core
-	PCHCTRL_GCLK_SERCOM6_CORE       = 36 // SERCOM6 Core
-	PCHCTRL_GCLK_SERCOM7_CORE       = 37 // SERCOM7 Core
-	PCHCTRL_GCLK_TCC4               = 38 // TCC4
-	PCHCTRL_GCLK_TC6                = 39
-	PCHCTRL_GCLK_TC7                = 39 // TC6, TC7
-	PCHCTRL_GCLK_ADC0               = 40 // ADC0
-	PCHCTRL_GCLK_ADC1               = 41 // ADC1
-	PCHCTRL_GCLK_DAC                = 42 // DAC
-	PCHCTRL_GCLK_I2S0               = 43
-	PCHCTRL_GCLK_I2S1               = 44
-	PCHCTRL_GCLK_SDHC0              = 45 // SDHC0
-	PCHCTRL_GCLK_SDHC1              = 46 // SDHC1
-	PCHCTRL_GCLK_CM4_TRACE          = 47 // CM4 Trace
-)
@@ -14,7 +14,7 @@ func main() {
 	led := machine.LED
 	led.Configure(machine.PinConfig{Mode: machine.PinOutput})

-	sensor := machine.ADC{Pin: machine.ADC2}
+	sensor := machine.ADC{machine.ADC2}
 	sensor.Configure(machine.ADCConfig{})

 	for {
@@ -1,12 +0,0 @@
-// +build arduino_mega1280
-
-package main
-
-import "machine"
-
-var (
-	// Configuration on an Arduino Uno.
-	pwm  = machine.Timer3
-	pinA = machine.PH3 // pin 6 on the Mega
-	pinB = machine.PH4 // pin 7 on the Mega
-)
@@ -1,12 +0,0 @@
-// +build arduino
-
-package main
-
-import "machine"
-
-var (
-	// Configuration on an Arduino Uno.
-	pwm  = machine.Timer2
-	pinA = machine.PB3 // pin 11 on the Uno
-	pinB = machine.PD3 // pin 3 on the Uno
-)
@@ -1,11 +0,0 @@
-// +build feather_m4
-
-package main
-
-import "machine"
-
-var (
-	pwm  = machine.TCC0
-	pinA = machine.D12
-	pinB = machine.D13
-)
@@ -1,11 +0,0 @@
-// +build itsybitsy_m0
-
-package main
-
-import "machine"
-
-var (
-	pwm  = machine.TCC0
-	pinA = machine.D3
-	pinB = machine.D4
-)
@@ -1,11 +0,0 @@
-// +build itsybitsy_m4
-
-package main
-
-import "machine"
-
-var (
-	pwm  = machine.TCC0
-	pinA = machine.D12
-	pinB = machine.D13
-)
@@ -1,74 +1,64 @@
 package main

-// This example demonstrates some features of the PWM support.
-
 import (
 	"machine"
 	"time"
 )

-const delayBetweenPeriods = time.Second * 5
+// This example assumes that an RGB LED is connected to pins 3, 5 and 6 on an Arduino.
+// Change the values below to use different pins.
+const (
+	redPin   = machine.D4
+	greenPin = machine.D5
+	bluePin  = machine.D6
+)

-func main() {
-	// Delay a bit on startup to easily catch the first messages.
-	time.Sleep(time.Second * 2)
-
-	// Configure the PWM with the given period.
-	err := pwm.Configure(machine.PWMConfig{
-		Period: 16384e3, // 16.384ms
-	})
-	if err != nil {
-		println("failed to configure PWM")
-		return
-	}
-
-	// The top value is the highest value that can be passed to PWMChannel.Set.
-	// It is usually an even number.
-	println("top:", pwm.Top())
-
-	// Configure the two channels we'll use as outputs.
-	channelA, err := pwm.Channel(pinA)
-	if err != nil {
-		println("failed to configure channel A")
-		return
-	}
-	channelB, err := pwm.Channel(pinB)
-	if err != nil {
-		println("failed to configure channel B")
-		return
-	}
-
-	// Invert one of the channels to demonstrate output polarity.
-	pwm.SetInverting(channelB, true)
-
-	// Test out various frequencies below, including some edge cases.
-
-	println("running at 0% duty cycle")
-	pwm.Set(channelA, 0)
-	pwm.Set(channelB, 0)
-	time.Sleep(delayBetweenPeriods)
-
-	println("running at 1")
-	pwm.Set(channelA, 1)
-	pwm.Set(channelB, 1)
-	time.Sleep(delayBetweenPeriods)
-
-	println("running at 25% duty cycle")
-	pwm.Set(channelA, pwm.Top()/4)
-	pwm.Set(channelB, pwm.Top()/4)
-	time.Sleep(delayBetweenPeriods)
-
-	println("running at top-1")
-	pwm.Set(channelA, pwm.Top()-1)
-	pwm.Set(channelB, pwm.Top()-1)
-	time.Sleep(delayBetweenPeriods)
-
-	println("running at 100% duty cycle")
-	pwm.Set(channelA, pwm.Top())
-	pwm.Set(channelB, pwm.Top())
-	time.Sleep(delayBetweenPeriods)
-
-	for {
-		time.Sleep(time.Second)
+// cycleColor is just a placeholder until math/rand or some equivalent is working.
+func cycleColor(color uint8) uint8 {
+	if color < 10 {
+		return color + 1
+	} else if color < 200 {
+		return color + 10
+	} else {
+		return 0
+	}
+}
+
+func main() {
+	machine.InitPWM()
+
+	red := machine.PWM{redPin}
+	err := red.Configure()
+	checkError(err, "failed to configure red pin")
+
+	green := machine.PWM{greenPin}
+	err = green.Configure()
+	checkError(err, "failed to configure green pin")
+
+	blue := machine.PWM{bluePin}
+	err = blue.Configure()
+	checkError(err, "failed to configure blue pin")
+
+	var rc uint8
+	var gc uint8 = 20
+	var bc uint8 = 30
+
+	for {
+		rc = cycleColor(rc)
+		gc = cycleColor(gc)
+		bc = cycleColor(bc)
+
+		red.Set(uint16(rc) << 8)
+		green.Set(uint16(gc) << 8)
+		blue.Set(uint16(bc) << 8)
+
+		time.Sleep(time.Millisecond * 500)
+	}
+}
+
+func checkError(err error, msg string) {
+	if err != nil {
+		print(msg, ": ", err.Error())
+		println()
 	}
 }
@@ -1,58 +0,0 @@
-.section .text.tinygo_startTask
-.global  tinygo_startTask
-.type    tinygo_startTask, %function
-tinygo_startTask:
-    .cfi_startproc
-    // Small assembly stub for starting a goroutine. This is already run on the
-    // new stack, with the callee-saved registers already loaded.
-    // Most importantly, EBX contain the pc of the to-be-started function and
-    // ESI contain the only argument it is given. Multiple arguments are packed
-    // into one by storing them in a new allocation.
-
-    // Indicate to the unwinder that there is nothing to unwind, this is the
-    // root frame. It avoids bogus extra frames in GDB.
-    .cfi_undefined eip
-
-    // Set the first argument of the goroutine start wrapper, which contains all
-    // the arguments.
-    pushl %esi
-
-    // Branch to the "goroutine start" function.
-    calll *%ebx
-
-    // Rebalance the stack (to undo the above push).
-    addl $4, %esp
-
-    // After return, exit this goroutine. This is a tail call.
-    jmp tinygo_pause
-    .cfi_endproc
-
-.global tinygo_swapTask
-.type tinygo_swapTask, %function
-tinygo_swapTask:
-    // This function gets the following parameters:
-    movl 4(%esp), %eax // newStack uintptr
-    movl 8(%esp), %ecx // oldStack *uintptr
-    // More information on the calling convention:
-    // https://wiki.osdev.org/System_V_ABI#i386
-
-    // Save all callee-saved registers:
-    pushl %ebp
-    pushl %edi
-    pushl %esi
-    pushl %ebx
-
-    // Save the current stack pointer in oldStack.
-    movl %esp, (%ecx)
-
-    // Switch to the new stack pointer.
-    movl %eax, %esp
-
-    // Load saved register from the new stack.
-    popl %ebx
-    popl %esi
-    popl %edi
-    popl %ebp
-
-    // Return into the new task, as if tinygo_swapTask was a regular call.
-    ret
@@ -1,59 +0,0 @@
-// +build scheduler.tasks,386
-
-package task
-
-import "unsafe"
-
-var systemStack uintptr
-
-// calleeSavedRegs is the list of registers that must be saved and restored when
-// switching between tasks. Also see task_stack_386.S that relies on the exact
-// layout of this struct.
-type calleeSavedRegs struct {
-	ebx uintptr
-	esi uintptr
-	edi uintptr
-	ebp uintptr
-
-	pc uintptr
-}
-
-// archInit runs architecture-specific setup for the goroutine startup.
-func (s *state) archInit(r *calleeSavedRegs, fn uintptr, args unsafe.Pointer) {
-	// Store the initial sp for the startTask function (implemented in assembly).
-	s.sp = uintptr(unsafe.Pointer(r))
-
-	// Initialize the registers.
-	// These will be popped off of the stack on the first resume of the goroutine.
-
-	// Start the function at tinygo_startTask (defined in
-	// src/internal/task/task_stack_386.S). This assembly code calls a function
-	// (passed in EBX) with a single argument (passed in ESI). After the
-	// function returns, it calls Pause().
-	r.pc = uintptr(unsafe.Pointer(&startTask))
-
-	// Pass the function to call in EBX.
-	// This function is a compiler-generated wrapper which loads arguments out
-	// of a struct pointer. See createGoroutineStartWrapper (defined in
-	// compiler/goroutine.go) for more information.
-	r.ebx = fn
-
-	// Pass the pointer to the arguments struct in ESI.
-	r.esi = uintptr(args)
-}
-
-func (s *state) resume() {
-	swapTask(s.sp, &systemStack)
-}
-
-func (s *state) pause() {
-	newStack := systemStack
-	systemStack = 0
-	swapTask(newStack, &s.sp)
-}
-
-// SystemStack returns the system stack pointer when called from a task stack.
-// When called from the system stack, it returns 0.
-func SystemStack() uintptr {
-	return systemStack
-}
@@ -1,74 +0,0 @@
-#ifdef __MACH__ // Darwin
-.global  _tinygo_startTask
-_tinygo_startTask:
-#else // Linux etc
-.section .text.tinygo_startTask
-.global  tinygo_startTask
-tinygo_startTask:
-#endif
-    .cfi_startproc
-    // Small assembly stub for starting a goroutine. This is already run on the
-    // new stack, with the callee-saved registers already loaded.
-    // Most importantly, r12 contain the pc of the to-be-started function and
-    // r13 contain the only argument it is given. Multiple arguments are packed
-    // into one by storing them in a new allocation.
-
-    // Indicate to the unwinder that there is nothing to unwind, this is the
-    // root frame. It avoids bogus extra frames in GDB like here:
-    //     #10 0x00000000004277b6 in <goroutine wrapper> () at [...]
-    //     #11 0x00000000004278f3 in tinygo_startTask () at [...]
-    //     #12 0x0000000000002030 in ?? ()
-    //     #13 0x0000000000000071 in ?? ()
-    .cfi_undefined rip
-
-    // Set the first argument of the goroutine start wrapper, which contains all
-    // the arguments.
-    movq %r13, %rdi
-
-    // Branch to the "goroutine start" function.
-    callq *%r12
-
-    // After return, exit this goroutine. This is a tail call.
-    #ifdef __MACH__
-    jmp _tinygo_pause
-    #else
-    jmp tinygo_pause
-    #endif
-    .cfi_endproc
-
-#ifdef __MACH__ // Darwin
-.global _tinygo_swapTask
-_tinygo_swapTask:
-#else // Linux etc
-.global tinygo_swapTask
-.section .text.tinygo_swapTask
-tinygo_swapTask:
-#endif
-    // This function gets the following parameters:
-    // %rdi = newStack uintptr
-    // %rsi = oldStack *uintptr
-
-    // Save all callee-saved registers:
-    pushq %r15
-    pushq %r14
-    pushq %r13
-    pushq %r12
-    pushq %rbp
-    pushq %rbx
-
-    // Save the current stack pointer in oldStack.
-    movq %rsp, (%rsi)
-
-    // Switch to the new stack pointer.
-    movq %rdi, %rsp
-
-    // Load saved register from the new stack.
-    popq %rbx
-    popq %rbp
-    popq %r12
-    popq %r13
-    popq %r14
-    popq %r15
-
-    // Return into the new task, as if tinygo_swapTask was a regular call.
-    ret
@@ -1,61 +0,0 @@
-// +build scheduler.tasks,amd64
-
-package task
-
-import "unsafe"
-
-var systemStack uintptr
-
-// calleeSavedRegs is the list of registers that must be saved and restored when
-// switching between tasks. Also see task_stack_amd64.S that relies on the exact
-// layout of this struct.
-type calleeSavedRegs struct {
-	rbx uintptr
-	rbp uintptr
-	r12 uintptr
-	r13 uintptr
-	r14 uintptr
-	r15 uintptr
-
-	pc uintptr
-}
-
-// archInit runs architecture-specific setup for the goroutine startup.
-func (s *state) archInit(r *calleeSavedRegs, fn uintptr, args unsafe.Pointer) {
-	// Store the initial sp for the startTask function (implemented in assembly).
-	s.sp = uintptr(unsafe.Pointer(r))
-
-	// Initialize the registers.
-	// These will be popped off of the stack on the first resume of the goroutine.
-
-	// Start the function at tinygo_startTask (defined in
-	// src/internal/task/task_stack_amd64.S). This assembly code calls a
-	// function (passed in r12) with a single argument (passed in r13). After
-	// the function returns, it calls Pause().
-	r.pc = uintptr(unsafe.Pointer(&startTask))
-
-	// Pass the function to call in r12.
-	// This function is a compiler-generated wrapper which loads arguments out
-	// of a struct pointer. See createGoroutineStartWrapper (defined in
-	// compiler/goroutine.go) for more information.
-	r.r12 = fn
-
-	// Pass the pointer to the arguments struct in r13.
-	r.r13 = uintptr(args)
-}
-
-func (s *state) resume() {
-	swapTask(s.sp, &systemStack)
-}
-
-func (s *state) pause() {
-	newStack := systemStack
-	systemStack = 0
-	swapTask(newStack, &s.sp)
-}
-
-// SystemStack returns the system stack pointer when called from a task stack.
-// When called from the system stack, it returns 0.
-func SystemStack() uintptr {
-	return systemStack
-}
@@ -1,51 +0,0 @@
-// Only generate .debug_frame, don't generate .eh_frame.
-.cfi_sections .debug_frame
-
-.section .text.tinygo_startTask
-.global  tinygo_startTask
-.type    tinygo_startTask, %function
-tinygo_startTask:
-    .cfi_startproc
-    // Small assembly stub for starting a goroutine. This is already run on the
-    // new stack, with the callee-saved registers already loaded.
-    // Most importantly, r4 contains the pc of the to-be-started function and r5
-    // contains the only argument it is given. Multiple arguments are packed
-    // into one by storing them in a new allocation.
-
-    // Indicate to the unwinder that there is nothing to unwind, this is the
-    // root frame. It avoids the following (bogus) error message in GDB:
-    //     Backtrace stopped: previous frame identical to this frame (corrupt stack?)
-    .cfi_undefined lr
-
-    // Set the first argument of the goroutine start wrapper, which contains all
-    // the arguments.
-    mov   r0, r5
-
-    // Branch to the "goroutine start" function. By using blx instead of bx,
-    // we'll return here instead of tail calling.
-    blx   r4
-
-    // After return, exit this goroutine. This is a tail call.
-    bl    tinygo_pause
-    .cfi_endproc
-.size tinygo_startTask, .-tinygo_startTask
-
-.global tinygo_swapTask
-.type tinygo_swapTask, %function
-tinygo_swapTask:
-    // This function gets the following parameters:
-    // r0 = newStack uintptr
-    // r1 = oldStack *uintptr
-
-    // Save all callee-saved registers:
-    push {r4-r11, lr}
-
-    // Save the current stack pointer in oldStack.
-    str sp, [r1]
-
-    // Switch to the new stack pointer.
-    mov sp, r0
-
-    // Load state from new task and branch to the previous position in the
-    // program.
-    pop {r4-r11, pc}
@@ -1,61 +0,0 @@
-// +build scheduler.tasks,arm,!cortexm,!avr,!xtensa
-
-package task
-
-import "unsafe"
-
-var systemStack uintptr
-
-// calleeSavedRegs is the list of registers that must be saved and restored when
-// switching between tasks. Also see task_stack_arm.S that relies on the exact
-// layout of this struct.
-type calleeSavedRegs struct {
-	r4  uintptr
-	r5  uintptr
-	r6  uintptr
-	r7  uintptr
-	r8  uintptr
-	r9  uintptr
-	r10 uintptr
-	r11 uintptr
-
-	pc uintptr
-}
-
-// archInit runs architecture-specific setup for the goroutine startup.
-func (s *state) archInit(r *calleeSavedRegs, fn uintptr, args unsafe.Pointer) {
-	// Store the initial sp for the startTask function (implemented in assembly).
-	s.sp = uintptr(unsafe.Pointer(r))
-
-	// Initialize the registers.
-	// These will be popped off of the stack on the first resume of the goroutine.
-
-	// Start the function at tinygo_startTask (defined in src/internal/task/task_stack_arm.S).
-	// This assembly code calls a function (passed in r4) with a single argument
-	// (passed in r5). After the function returns, it calls Pause().
-	r.pc = uintptr(unsafe.Pointer(&startTask))
-
-	// Pass the function to call in r4.
-	// This function is a compiler-generated wrapper which loads arguments out of a struct pointer.
-	// See createGoroutineStartWrapper (defined in compiler/goroutine.go) for more information.
-	r.r4 = fn
-
-	// Pass the pointer to the arguments struct in r5.
-	r.r5 = uintptr(args)
-}
-
-func (s *state) resume() {
-	swapTask(s.sp, &systemStack)
-}
-
-func (s *state) pause() {
-	newStack := systemStack
-	systemStack = 0
-	swapTask(newStack, &s.sp)
-}
-
-// SystemStack returns the system stack pointer when called from a task stack.
-// When called from the system stack, it returns 0.
-func SystemStack() uintptr {
-	return systemStack
-}
@@ -1,59 +0,0 @@
-.section .text.tinygo_startTask
-.global  tinygo_startTask
-.type    tinygo_startTask, %function
-tinygo_startTask:
-    .cfi_startproc
-    // Small assembly stub for starting a goroutine. This is already run on the
-    // new stack, with the callee-saved registers already loaded.
-    // Most importantly, x19 contains the pc of the to-be-started function and
-    // x20 contains the only argument it is given. Multiple arguments are packed
-    // into one by storing them in a new allocation.
-
-    // Indicate to the unwinder that there is nothing to unwind, this is the
-    // root frame. It avoids the following (bogus) error message in GDB:
-    //     Backtrace stopped: previous frame identical to this frame (corrupt stack?)
-    .cfi_undefined lr
-
-    // Set the first argument of the goroutine start wrapper, which contains all
-    // the arguments.
-    mov   x0, x20
-
-    // Branch to the "goroutine start" function. By using blx instead of bx,
-    // we'll return here instead of tail calling.
-    blr   x19
-
-    // After return, exit this goroutine. This is a tail call.
-    b     tinygo_pause
-    .cfi_endproc
-.size tinygo_startTask, .-tinygo_startTask
-
-.global tinygo_swapTask
-.type tinygo_swapTask, %function
-tinygo_swapTask:
-    // This function gets the following parameters:
-    // x0 = newStack uintptr
-    // x1 = oldStack *uintptr
-
-    // Save all callee-saved registers:
-    stp     x19, x20, [sp, #-96]!
-    stp     x21, x22, [sp, #16]
-    stp     x23, x24, [sp, #32]
-    stp     x25, x26, [sp, #48]
-    stp     x27, x28, [sp, #64]
-    stp     x29, x30, [sp, #80]
-
-    // Save the current stack pointer in oldStack.
-    mov x8, sp
-    str x8, [x1]
-
-    // Switch to the new stack pointer.
-    mov sp, x0
-
-    // Restore stack state and return.
-    ldp     x29, x30, [sp, #80]
-    ldp     x27, x28, [sp, #64]
-    ldp     x25, x26, [sp, #48]
-    ldp     x23, x24, [sp, #32]
-    ldp     x21, x22, [sp, #16]
-    ldp     x19, x20, [sp], #96
-    ret
@@ -1,64 +0,0 @@
-// +build scheduler.tasks,arm64
-
-package task
-
-import "unsafe"
-
-var systemStack uintptr
-
-// calleeSavedRegs is the list of registers that must be saved and restored when
-// switching between tasks. Also see task_stack_arm64.S that relies on the exact
-// layout of this struct.
-type calleeSavedRegs struct {
-	x19 uintptr
-	x20 uintptr
-	x21 uintptr
-	x22 uintptr
-	x23 uintptr
-	x24 uintptr
-	x25 uintptr
-	x26 uintptr
-	x27 uintptr
-	x28 uintptr
-	x29 uintptr
-
-	pc uintptr // aka x30 aka LR
-}
-
-// archInit runs architecture-specific setup for the goroutine startup.
-func (s *state) archInit(r *calleeSavedRegs, fn uintptr, args unsafe.Pointer) {
-	// Store the initial sp for the startTask function (implemented in assembly).
-	s.sp = uintptr(unsafe.Pointer(r))
-
-	// Initialize the registers.
-	// These will be popped off of the stack on the first resume of the goroutine.
-
-	// Start the function at tinygo_startTask (defined in src/internal/task/task_stack_arm64.S).
-	// This assembly code calls a function (passed in x19) with a single argument
-	// (passed in x20). After the function returns, it calls Pause().
-	r.pc = uintptr(unsafe.Pointer(&startTask))
-
-	// Pass the function to call in x19.
-	// This function is a compiler-generated wrapper which loads arguments out of a struct pointer.
-	// See createGoroutineStartWrapper (defined in compiler/goroutine.go) for more information.
-	r.x19 = fn
-
-	// Pass the pointer to the arguments struct in x20.
-	r.x20 = uintptr(args)
-}
-
-func (s *state) resume() {
-	swapTask(s.sp, &systemStack)
-}
-
-func (s *state) pause() {
-	newStack := systemStack
-	systemStack = 0
-	swapTask(newStack, &s.sp)
-}
-
-// SystemStack returns the system stack pointer when called from a task stack.
-// When called from the system stack, it returns 0.
-func SystemStack() uintptr {
-	return systemStack
-}
@@ -2,12 +2,6 @@

 package task

-// Note that this is almost the same as task_stack_arm.go, but it uses the MSP
-// register to store the system stack pointer instead of a global variable. The
-// big advantage of this is that interrupts always execute with MSP (and not
-// PSP, which is used for goroutines) so that goroutines do not need extra stack
-// space for interrupts.
-
 import (
 	"device/arm"
 	"unsafe"
@@ -9,11 +9,4 @@ type ADCConfig struct {
 	Reference  uint32 // analog reference voltage (AREF) in millivolts
 	Resolution uint32 // number of bits for a single conversion (e.g., 8, 10, 12)
 	Samples    uint32 // number of samples for a single conversion (e.g., 4, 8, 16, 32)
-	Bus        uint8  // bus Number of ADC
 }
-
-const (
-	AdcBusAuto = 0
-	AdcBus0    = 1
-	AdcBus1    = 2
-)
@@ -1,104 +0,0 @@
-// +build arduino_mega1280
-
-package machine
-
-// Return the current CPU frequency in hertz.
-func CPUFrequency() uint32 {
-	return 16000000
-}
-
-const (
-	AREF Pin = NoPin
-	LED  Pin = PB7
-
-	A0  Pin = PF0
-	A1  Pin = PF1
-	A2  Pin = PF2
-	A3  Pin = PF3
-	A4  Pin = PF4
-	A5  Pin = PF5
-	A6  Pin = PF6
-	A7  Pin = PF7
-	A8  Pin = PK0
-	A9  Pin = PK1
-	A10 Pin = PK2
-	A11 Pin = PK3
-	A12 Pin = PK4
-	A13 Pin = PK5
-	A14 Pin = PK6
-	A15 Pin = PK7
-
-	// Analog Input
-	ADC0  Pin = PF0
-	ADC1  Pin = PF1
-	ADC2  Pin = PF2
-	ADC3  Pin = PF3
-	ADC4  Pin = PF4
-	ADC5  Pin = PF5
-	ADC6  Pin = PF6
-	ADC7  Pin = PF7
-	ADC8  Pin = PK0
-	ADC9  Pin = PK1
-	ADC10 Pin = PK2
-	ADC11 Pin = PK3
-	ADC12 Pin = PK4
-	ADC13 Pin = PK5
-	ADC14 Pin = PK6
-	ADC15 Pin = PK7
-
-	// Digital pins
-	D0  Pin = PE0
-	D1  Pin = PE1
-	D2  Pin = PE4
-	D3  Pin = PE5
-	D4  Pin = PG5
-	D5  Pin = PE3
-	D6  Pin = PH3
-	D7  Pin = PH4
-	D8  Pin = PH5
-	D9  Pin = PH6
-	D10 Pin = PB4
-	D11 Pin = PB5
-	D12 Pin = PB6
-	D13 Pin = PB7
-	D14 Pin = PJ1
-	D15 Pin = PJ0
-	D16 Pin = PH1
-	D17 Pin = PH0
-	D18 Pin = PD3
-	D19 Pin = PD2
-	D20 Pin = PD1
-	D21 Pin = PD0
-	D22 Pin = PA0
-	D23 Pin = PA1
-	D24 Pin = PA2
-	D25 Pin = PA3
-	D26 Pin = PA4
-	D27 Pin = PA5
-	D28 Pin = PA6
-	D29 Pin = PA7
-	D30 Pin = PC7
-	D31 Pin = PC6
-	D32 Pin = PC5
-	D33 Pin = PC4
-	D34 Pin = PC3
-	D35 Pin = PC2
-	D36 Pin = PC1
-	D37 Pin = PC0
-	D38 Pin = PD7
-	D39 Pin = PG2
-	D40 Pin = PG1
-	D41 Pin = PG0
-	D42 Pin = PL7
-	D43 Pin = PL6
-	D44 Pin = PL5
-	D45 Pin = PL4
-	D46 Pin = PL3
-	D47 Pin = PL2
-	D48 Pin = PL1
-	D49 Pin = PL0
-	D50 Pin = PB3
-	D51 Pin = PB2
-	D52 Pin = PB1
-	D53 Pin = PB0
-)
@@ -1,330 +0,0 @@
-// +build atsame54_xpro
-
-package machine
-
-import (
-	"device/sam"
-	"runtime/interrupt"
-)
-
-// Definition for compatibility, but not used
-const RESET_MAGIC_VALUE = 0x00000000
-
-const (
-	LED    = PC18
-	BUTTON = PB31
-)
-
-const (
-	// https://ww1.microchip.com/downloads/en/DeviceDoc/70005321A.pdf
-
-	// Extension Header EXT1
-	EXT1_PIN3_ADC_P     = PB04
-	EXT1_PIN4_ADC_N     = PB05
-	EXT1_PIN5_GPIO1     = PA06
-	EXT1_PIN6_GPIO2     = PA07
-	EXT1_PIN7_PWM_P     = PB08
-	EXT1_PIN8_PWM_N     = PB09
-	EXT1_PIN9_IRQ       = PB07
-	EXT1_PIN9_GPIO      = PB07
-	EXT1_PIN10_SPI_SS_B = PA27
-	EXT1_PIN10_GPIO     = PA27
-	EXT1_PIN11_TWI_SDA  = PA22
-	EXT1_PIN12_TWI_SCL  = PA23
-	EXT1_PIN13_UART_RX  = PA05
-	EXT1_PIN14_UART_TX  = PA04
-	EXT1_PIN15_SPI_SS_A = PB28
-	EXT1_PIN16_SPI_SDO  = PB27
-	EXT1_PIN17_SPI_SDI  = PB29
-	EXT1_PIN18_SPI_SCK  = PB26
-
-	// Extension Header EXT2
-	EXT2_PIN3_ADC_P     = PB00
-	EXT2_PIN4_ADC_N     = PA03
-	EXT2_PIN5_GPIO1     = PB01
-	EXT2_PIN6_GPIO2     = PB06
-	EXT2_PIN7_PWM_P     = PB14
-	EXT2_PIN8_PWM_N     = PB15
-	EXT2_PIN9_IRQ       = PD00
-	EXT2_PIN9_GPIO      = PD00
-	EXT2_PIN10_SPI_SS_B = PB02
-	EXT2_PIN10_GPIO     = PB02
-	EXT2_PIN11_TWI_SDA  = PD08
-	EXT2_PIN12_TWI_SCL  = PD09
-	EXT2_PIN13_UART_RX  = PB17
-	EXT2_PIN14_UART_TX  = PB16
-	EXT2_PIN15_SPI_SS_A = PC06
-	EXT2_PIN16_SPI_SDO  = PC04
-	EXT2_PIN17_SPI_SDI  = PC07
-	EXT2_PIN18_SPI_SCK  = PC05
-
-	// Extension Header EXT3
-	EXT3_PIN3_ADC_P     = PC02
-	EXT3_PIN4_ADC_N     = PC03
-	EXT3_PIN5_GPIO1     = PC01
-	EXT3_PIN6_GPIO2     = PC10
-	EXT3_PIN7_PWM_P     = PD10
-	EXT3_PIN8_PWM_N     = PD11
-	EXT3_PIN9_IRQ       = PC30
-	EXT3_PIN9_GPIO      = PC30
-	EXT3_PIN10_SPI_SS_B = PC31
-	EXT3_PIN10_GPIO     = PC31
-	EXT3_PIN11_TWI_SDA  = PD08
-	EXT3_PIN12_TWI_SCL  = PD09
-	EXT3_PIN13_UART_RX  = PC23
-	EXT3_PIN14_UART_TX  = PC22
-	EXT3_PIN15_SPI_SS_A = PC14
-	EXT3_PIN16_SPI_SDO  = PC04
-	EXT3_PIN17_SPI_SDI  = PC07
-	EXT3_PIN18_SPI_SCK  = PC05
-
-	// SD_CARD
-	SD_CARD_MCDA0   = PB18
-	SD_CARD_MCDA1   = PB19
-	SD_CARD_MCDA2   = PB20
-	SD_CARD_MCDA3   = PB21
-	SD_CARD_MCCK    = PA21
-	SD_CARD_MCCDA   = PA20
-	SD_CARD_DETECT  = PD20
-	SD_CARD_PROTECT = PD21
-
-	// I2C
-	I2C_SDA = PD08
-	I2C_SCL = PD09
-
-	// CAN
-	CAN0_TX = PA22
-	CAN0_RX = PA23
-
-	CAN1_STANDBY = PC13
-	CAN1_TX      = PB12
-	CAN1_RX      = PB13
-
-	CAN_STANDBY = CAN1_STANDBY
-	CAN_TX      = CAN1_TX
-	CAN_RX      = CAN1_RX
-
-	// PDEC
-	PDEC_PHASE_A = PC16
-	PDEC_PHASE_B = PC17
-	PDEC_INDEX   = PC18
-
-	// PCC
-	PCC_I2C_SDA    = PD08
-	PCC_I2C_SCL    = PD09
-	PCC_VSYNC_DEN1 = PA12
-	PCC_HSYNC_DEN2 = PA13
-	PCC_CLK        = PA14
-	PCC_XCLK       = PA15
-	PCC_DATA00     = PA16
-	PCC_DATA01     = PA17
-	PCC_DATA02     = PA18
-	PCC_DATA03     = PA19
-	PCC_DATA04     = PA20
-	PCC_DATA05     = PA21
-	PCC_DATA06     = PA22
-	PCC_DATA07     = PA23
-	PCC_DATA08     = PB14
-	PCC_DATA09     = PB15
-	PCC_RESET      = PC12
-	PCC_PWDN       = PC11
-
-	// Ethernet
-	ETHERNET_TXCK  = PA14
-	ETHERNET_TXEN  = PA17
-	ETHERNET_TX0   = PA18
-	ETHERNET_TX1   = PA19
-	ETHERNET_RXER  = PA15
-	ETHERNET_RX0   = PA13
-	ETHERNET_RX1   = PA12
-	ETHERNET_RXDV  = PC20
-	ETHERNET_MDIO  = PC12
-	ETHERNET_MDC   = PC11
-	ETHERNET_INT   = PD12
-	ETHERNET_RESET = PC21
-
-	PIN_QT_BUTTON   = PA16
-	PIN_BTN0        = PB31
-	PIN_ETH_LED     = PC15
-	PIN_LED0        = PC18
-	PIN_ADC_DAC     = PA02
-	PIN_VBUS_DETECT = PC00
-	PIN_USB_ID      = PC19
-)
-
-// UART0 aka USBCDC pins
-const (
-	USBCDC_DM_PIN = PA24
-	USBCDC_DP_PIN = PA25
-)
-
-// UART pins
-const (
-	// Extension Header EXT1
-	UART_TX_PIN = PA04 // TX : SERCOM0/PAD[0]
-	UART_RX_PIN = PA05 // RX : SERCOM0/PAD[1]
-
-	// Extension Header EXT2
-	UART2_TX_PIN = PB16 // TX : SERCOM5/PAD[0]
-	UART2_RX_PIN = PB17 // RX : SERCOM5/PAD[1]
-
-	// Extension Header EXT3
-	UART3_TX_PIN = PC22 // TX : SERCOM1/PAD[0]
-	UART3_RX_PIN = PC23 // RX : SERCOM1/PAD[1]
-
-	// Virtual COM Port
-	UART4_TX_PIN = PB25 // TX : SERCOM2/PAD[0]
-	UART4_RX_PIN = PB24 // RX : SERCOM2/PAD[1]
-)
-
-// I2C pins
-const (
-	// Extension Header EXT1
-	SDA0_PIN = PA22 // SDA: SERCOM3/PAD[0]
-	SCL0_PIN = PA23 // SCL: SERCOM3/PAD[1]
-
-	// Extension Header EXT2
-	SDA1_PIN = PD08 // SDA: SERCOM7/PAD[0]
-	SCL1_PIN = PD09 // SCL: SERCOM7/PAD[1]
-
-	// Extension Header EXT3
-	SDA2_PIN = PD08 // SDA: SERCOM7/PAD[0]
-	SCL2_PIN = PD09 // SCL: SERCOM7/PAD[1]
-
-	// Data Gateway Interface
-	SDA_DGI_PIN = PD08 // SDA: SERCOM7/PAD[0]
-	SCL_DGI_PIN = PD09 // SCL: SERCOM7/PAD[1]
-
-	SDA_PIN = SDA0_PIN
-	SCL_PIN = SCL0_PIN
-)
-
-// SPI pins
-const (
-	// Extension Header EXT1
-	SPI0_SCK_PIN = PB26 // SCK: SERCOM4/PAD[1]
-	SPI0_SDO_PIN = PB27 // SDO: SERCOM4/PAD[0]
-	SPI0_SDI_PIN = PB29 // SDI: SERCOM4/PAD[3]
-	SPI0_SS_PIN  = PB28 // SS : SERCOM4/PAD[2]
-
-	// Extension Header EXT2
-	SPI1_SCK_PIN = PC05 // SCK: SERCOM6/PAD[1]
-	SPI1_SDO_PIN = PC04 // SDO: SERCOM6/PAD[0]
-	SPI1_SDI_PIN = PC07 // SDI: SERCOM6/PAD[3]
-	SPI1_SS_PIN  = PC06 // SS : SERCOM6/PAD[2]
-
-	// Extension Header EXT3
-	SPI2_SCK_PIN = PC05 // SCK: SERCOM6/PAD[1]
-	SPI2_SDO_PIN = PC04 // SDO: SERCOM6/PAD[0]
-	SPI2_SDI_PIN = PC07 // SDI: SERCOM6/PAD[3]
-	SPI2_SS_PIN  = PC14 // SS : GPIO
-
-	// Data Gateway Interface
-	SPI_DGI_SCK_PIN = PC05 // SCK: SERCOM6/PAD[1]
-	SPI_DGI_SDO_PIN = PC04 // SDO: SERCOM6/PAD[0]
-	SPI_DGI_SDI_PIN = PC07 // SDI: SERCOM6/PAD[3]
-	SPI_DGI_SS_PIN  = PD01 // SS : GPIO
-)
-
-// USB CDC identifiers
-const (
-	usb_STRING_PRODUCT      = "SAM E54 Xplained Pro"
-	usb_STRING_MANUFACTURER = "Atmel"
-)
-
-var (
-	usb_VID uint16 = 0x03EB
-	usb_PID uint16 = 0x2404
-)
-
-// UART on the SAM E54 Xplained Pro
-var (
-	// Extension Header EXT1
-	UART1 = UART{
-		Buffer: NewRingBuffer(),
-		Bus:    sam.SERCOM0_USART_INT,
-		SERCOM: 0,
-	}
-
-	// Extension Header EXT2
-	UART2 = UART{
-		Buffer: NewRingBuffer(),
-		Bus:    sam.SERCOM5_USART_INT,
-		SERCOM: 5,
-	}
-
-	// Extension Header EXT3
-	UART3 = UART{
-		Buffer: NewRingBuffer(),
-		Bus:    sam.SERCOM1_USART_INT,
-		SERCOM: 1,
-	}
-
-	// EDBG Virtual COM Port
-	UART4 = UART{
-		Buffer: NewRingBuffer(),
-		Bus:    sam.SERCOM2_USART_INT,
-		SERCOM: 2,
-	}
-)
-
-func init() {
-	UART1.Interrupt = interrupt.New(sam.IRQ_SERCOM0_2, UART1.handleInterrupt)
-	UART2.Interrupt = interrupt.New(sam.IRQ_SERCOM5_2, UART2.handleInterrupt)
-	UART3.Interrupt = interrupt.New(sam.IRQ_SERCOM1_2, UART3.handleInterrupt)
-	UART4.Interrupt = interrupt.New(sam.IRQ_SERCOM2_2, UART4.handleInterrupt)
-}
-
-// I2C on the SAM E54 Xplained Pro
-var (
-	// Extension Header EXT1
-	I2C0 = I2C{
-		Bus:    sam.SERCOM3_I2CM,
-		SERCOM: 3,
-	}
-
-	// Extension Header EXT2
-	I2C1 = I2C{
-		Bus:    sam.SERCOM7_I2CM,
-		SERCOM: 7,
-	}
-
-	// Extension Header EXT3
-	I2C2 = I2C{
-		Bus:    sam.SERCOM7_I2CM,
-		SERCOM: 7,
-	}
-
-	// Data Gateway Interface
-	I2C3 = I2C{
-		Bus:    sam.SERCOM7_I2CM,
-		SERCOM: 7,
-	}
-)
-
-// SPI on the SAM E54 Xplained Pro
-var (
-	// Extension Header EXT1
-	SPI0 = SPI{
-		Bus:    sam.SERCOM4_SPIM,
-		SERCOM: 4,
-	}
-
-	// Extension Header EXT2
-	SPI1 = SPI{
-		Bus:    sam.SERCOM6_SPIM,
-		SERCOM: 6,
-	}
-
-	// Extension Header EXT3
-	SPI2 = SPI{
-		Bus:    sam.SERCOM6_SPIM,
-		SERCOM: 6,
-	}
-
-	// Data Gateway Interface
-	SPI3 = SPI{
-		Bus:    sam.SERCOM6_SPIM,
-		SERCOM: 6,
-	}
-)
@@ -25,8 +25,8 @@ const (

 // Analog Pins
 const (
-	A0  = PA02 // ADC/AIN[0]
-	A1  = PA05 // PWM available, also ADC/AIN[5]
+	A0  = PA02 // PWM available, also ADC/AIN[0]
+	A1  = PA05 // ADC/AIN[5]
 	A2  = PA06 // PWM available, also ADC/AIN[6]
 	A3  = PA07 // PWM available, also ADC/AIN[7]
 	A4  = PB03 // PORTB
@@ -1,142 +0,0 @@
-// +build feather_m4_can
-
-package machine
-
-import (
-	"device/sam"
-	"runtime/interrupt"
-)
-
-// used to reset into bootloader
-const RESET_MAGIC_VALUE = 0xf01669ef
-
-// GPIO Pins
-const (
-	D0  = PB17 // UART0 RX/PWM available
-	D1  = PB16 // UART0 TX/PWM available
-	D4  = PA14 // PWM available
-	D5  = PA16 // PWM available
-	D6  = PA18 // PWM available
-	D7  = PB03 // neopixel power
-	D8  = PB02 // built-in neopixel
-	D9  = PA19 // PWM available
-	D10 = PA20 // can be used for PWM or UART1 TX
-	D11 = PA21 // can be used for PWM or UART1 RX
-	D12 = PA22 // PWM available
-	D13 = PA23 // PWM available
-	D21 = PA13 // PWM available
-	D22 = PA12 // PWM available
-	D23 = PB22 // PWM available
-	D24 = PB23 // PWM available
-	D25 = PA17 // PWM available
-)
-
-// Analog pins
-const (
-	A0 = PA02 // ADC/AIN[0]
-	A1 = PA05 // ADC/AIN[2]
-	A2 = PB08 // ADC/AIN[3]
-	A3 = PB09 // ADC/AIN[4]
-	A4 = PA04 // ADC/AIN[5]
-	A5 = PA06 // ADC/AIN[10]
-)
-
-const (
-	LED       = D13
-	NEOPIXELS = D8
-)
-
-// UART0 aka USBCDC pins
-const (
-	USBCDC_DM_PIN = PA24
-	USBCDC_DP_PIN = PA25
-)
-
-const (
-	UART_TX_PIN = D1
-	UART_RX_PIN = D0
-)
-
-const (
-	UART2_TX_PIN = A4
-	UART2_RX_PIN = A5
-)
-
-// I2C pins
-const (
-	SDA_PIN = D22 // SDA: SERCOM2/PAD[0]
-	SCL_PIN = D21 // SCL: SERCOM2/PAD[1]
-)
-
-// SPI pins
-const (
-	SPI0_SCK_PIN = D25 // SCK: SERCOM1/PAD[1]
-	SPI0_SDO_PIN = D24 // SDO: SERCOM1/PAD[3]
-	SPI0_SDI_PIN = D23 // SDI: SERCOM1/PAD[2]
-)
-
-// CAN pins
-const (
-	CAN0_TX = PA22
-	CAN0_RX = PA23
-
-	CAN1_STANDBY = PB12
-	CAN1_TX      = PB14
-	CAN1_RX      = PB15
-	BOOST_EN     = PB13 // power control of CAN1's TCAN1051HGV (H: enable)
-
-	CAN_STANDBY = CAN1_STANDBY
-	CAN_S       = CAN1_STANDBY
-	CAN_TX      = CAN1_TX
-	CAN_RX      = CAN1_RX
-)
-
-// USB CDC identifiers
-const (
-	usb_STRING_PRODUCT      = "Adafruit Feather M4 CAN"
-	usb_STRING_MANUFACTURER = "Adafruit"
-)
-
-var (
-	usb_VID uint16 = 0x239A
-	usb_PID uint16 = 0x80CD
-)
-
-var (
-	UART1 = UART{
-		Buffer: NewRingBuffer(),
-		Bus:    sam.SERCOM5_USART_INT,
-		SERCOM: 5,
-	}
-
-	UART2 = UART{
-		Buffer: NewRingBuffer(),
-		Bus:    sam.SERCOM0_USART_INT,
-		SERCOM: 0,
-	}
-)
-
-func init() {
-	UART1.Interrupt = interrupt.New(sam.IRQ_SERCOM5_2, UART1.handleInterrupt)
-	UART2.Interrupt = interrupt.New(sam.IRQ_SERCOM0_2, UART2.handleInterrupt)
-
-	// turn on neopixel
-	D7.Configure(PinConfig{Mode: PinOutput})
-	D7.High()
-}
-
-// I2C on the Feather M4.
-var (
-	I2C0 = &I2C{
-		Bus:    sam.SERCOM2_I2CM,
-		SERCOM: 2,
-	}
-)
-
-// SPI on the Feather M4.
-var (
-	SPI0 = SPI{
-		Bus:    sam.SERCOM1_SPIM,
-		SERCOM: 1,
-	}
-)
@@ -41,17 +41,13 @@ const (
 	// LORA RFM95 Radio
 	RFM95_DIO0_PIN = PC13

-	// TinyGo UART is MCU LPUSART1
+	//TinyGo UART is MCU LPUSART1
 	UART_RX_PIN = PA13
 	UART_TX_PIN = PA14

-	// TinyGo UART1 is MCU USART1
+	//TinyGo UART1 is MCU USART1
 	UART1_RX_PIN = PB6
 	UART1_TX_PIN = PB7
-
-	// MPU9250 Nine-Axis (Gyro + Accelerometer + Compass)
-	I2C0_SCL_PIN = PA9
-	I2C0_SDA_PIN = PA10
 )

 var (
@@ -72,13 +68,6 @@ var (
 		RxAltFuncSelector: 0,
 	}

-	// MPU9250 Nine-Axis (Gyro + Accelerometer + Compass)
-	I2C1 = &I2C{
-		Bus:             stm32.I2C1,
-		AltFuncSelector: 6,
-	}
-	I2C0 = I2C1
-
 	// SPI
 	SPI0 = SPI{
 		Bus: stm32.SPI1,
@@ -5,6 +5,11 @@ package machine
 // The micro:bit does not have a 32kHz crystal on board.
 const HasLowFrequencyCrystal = false

+const (
+	LED  = P13
+	LED1 = LED
+)
+
 // Buttons on the micro:bit v2 (A and B)
 const (
 	BUTTON  Pin = BUTTONA
@@ -1,92 +0,0 @@
-// +build nucleol031k6
-
-package machine
-
-import (
-	"device/stm32"
-	"runtime/interrupt"
-)
-
-const (
-	LED         = LED_BUILTIN
-	LED_BUILTIN = LED_GREEN
-	LED_GREEN   = PB3
-)
-
-const (
-	// Arduino Pins
-	A0 = PA0 // ADC_IN0
-	A1 = PA1 // ADC_IN1
-	A2 = PA3 // ADC_IN3
-	A3 = PA4 // ADC_IN4
-	A4 = PA5 // ADC_IN5 || I2C1_SDA
-	A5 = PA6 // ADC_IN6 || I2C1_SCL
-	A6 = PA7 // ADC_IN7
-	A7 = PA2 // ADC_IN2
-
-	D0  = PA10 // USART1_TX
-	D1  = PA9  // USART1_RX
-	D2  = PA12
-	D3  = PB0 // TIM2_CH3
-	D4  = PB7
-	D5  = PB6  // TIM16_CH1N
-	D6  = PB1  // TIM14_CH1
-	D9  = PA8  // TIM1_CH1
-	D10 = PA11 // SPI_CS || TIM1_CH4
-	D11 = PB5  // SPI1_MOSI || TIM3_CH2
-	D12 = PB4  // SPI1_MISO
-	D13 = PB3  // SPI1_SCK
-)
-
-const (
-	// UART pins
-	// PA2 and PA15 are connected to the ST-Link Virtual Com Port (VCP)
-	UART_TX_PIN = PA2
-	UART_RX_PIN = PA15
-
-	// SPI
-	SPI1_SCK_PIN = PB3
-	SPI1_SDI_PIN = PB5
-	SPI1_SDO_PIN = PB4
-	SPI0_SCK_PIN = SPI1_SCK_PIN
-	SPI0_SDI_PIN = SPI1_SDI_PIN
-	SPI0_SDO_PIN = SPI1_SDO_PIN
-
-	// I2C pins
-	// PB6 and PB7 are mapped to CN4 pin 7 and CN4 pin 8 respectively with the
-	// default solder bridge settings
-	I2C0_SCL_PIN  = PB7
-	I2C0_SDA_PIN  = PB6
-	I2C0_ALT_FUNC = 1
-)
-
-var (
-	// USART2 is the hardware serial port connected to the onboard ST-LINK
-	// debugger to be exposed as virtual COM port over USB on Nucleo boards.
-	// Both UART0 and UART1 refer to USART2.
-	UART0 = UART{
-		Buffer:            NewRingBuffer(),
-		Bus:               stm32.USART2,
-		TxAltFuncSelector: 4,
-		RxAltFuncSelector: 4,
-	}
-	UART1 = &UART0
-
-	// I2C1 is documented, alias to I2C0 as well
-	I2C1 = &I2C{
-		Bus:             stm32.I2C1,
-		AltFuncSelector: 1,
-	}
-	I2C0 = I2C1
-
-	// SPI
-	SPI0 = SPI{
-		Bus:             stm32.SPI1,
-		AltFuncSelector: 0,
-	}
-	SPI1 = &SPI0
-)
-
-func init() {
-	UART0.Interrupt = interrupt.New(stm32.IRQ_USART2, UART0.handleInterrupt)
-}
@@ -13,53 +13,20 @@ const (
 	LED_GREEN   = PB3
 )

+// UART pins
 const (
-	// Arduino Pins
-	A0 = PA0
-	A1 = PA1
-	A2 = PA3
-	A3 = PA4
-	A4 = PA5
-	A5 = PA6
-	A6 = PA7
-	A7 = PA2
-
-	D0  = PA10
-	D1  = PA9
-	D2  = PA12
-	D3  = PB0
-	D4  = PB7
-	D5  = PB6
-	D6  = PB1
-	D7  = PC14
-	D8  = PC15
-	D9  = PA8
-	D10 = PA11
-	D11 = PB5
-	D12 = PB4
-	D13 = PB3
-)
-
-const (
-	// UART pins
 	// PA2 and PA15 are connected to the ST-Link Virtual Com Port (VCP)
 	UART_TX_PIN = PA2
 	UART_RX_PIN = PA15
+)

-	// I2C pins
+// I2C pins
+const (
 	// With default solder bridge settings:
 	//    PB6 / Arduino D5 / CN3 Pin 8 is SCL
 	//    PB7 / Arduino D4 / CN3 Pin 7 is SDA
 	I2C0_SCL_PIN = PB6
 	I2C0_SDA_PIN = PB7
-
-	// SPI pins
-	SPI1_SCK_PIN = PB3
-	SPI1_SDI_PIN = PB5
-	SPI1_SDO_PIN = PB4
-	SPI0_SCK_PIN = SPI1_SCK_PIN
-	SPI0_SDI_PIN = SPI1_SDI_PIN
-	SPI0_SDO_PIN = SPI1_SDO_PIN
 )

 var (
@@ -73,20 +40,15 @@ var (
 		RxAltFuncSelector: 3,
 	}
 	UART1 = &UART0
+)

+var (
 	// I2C1 is documented, alias to I2C0 as well
 	I2C1 = &I2C{
 		Bus:             stm32.I2C1,
 		AltFuncSelector: 4,
 	}
 	I2C0 = I2C1
-
-	// SPI1 is documented, alias to SPI0 as well
-	SPI1 = &SPI{
-		Bus:             stm32.SPI1,
-		AltFuncSelector: 5,
-	}
-	SPI0 = SPI1
 )

 func init() {
@@ -94,8 +94,8 @@ const (
 // I2C on the QT Py M0.
 var (
 	I2C0 = &I2C{
-		Bus:    sam.SERCOM1_I2CM,
-		SERCOM: 1,
+		Bus:    sam.SERCOM2_I2CM,
+		SERCOM: 2,
 	}
 )

@@ -1,4 +1,4 @@
-// +build atmega nrf sam stm32 fe310 k210
+// +build atmega nrf sam stm32,!stm32l0 fe310 k210

 package machine

@@ -10,11 +10,6 @@ var (
 	ErrNoPinChangeChannel = errors.New("machine: no channel available for pin interrupt")
 )

-// PinMode sets the direction and pull mode of the pin. For example, PinOutput
-// sets the pin as an output and PinInputPullup sets the pin as an input with a
-// pull-up.
-type PinMode uint8
-
 type PinConfig struct {
 	Mode PinMode
 }
@@ -42,7 +37,10 @@ func (p Pin) Low() {
 	p.Set(false)
 }

+type PWM struct {
+	Pin Pin
+}
+
 type ADC struct {
 	Pin Pin
-	Bus uint8
 }
@@ -1,931 +0,0 @@
-// +build avr,atmega1280
-
-package machine
-
-import (
-	"device/avr"
-	"runtime/interrupt"
-	"runtime/volatile"
-)
-
-const irq_USART0_RX = avr.IRQ_USART0_RX
-
-const (
-	portA Pin = iota * 8
-	portB
-	portC
-	portD
-	portE
-	portF
-	portG
-	portH
-	portJ
-	portK
-	portL
-)
-
-const (
-	PA0 = portA + 0
-	PA1 = portA + 1
-	PA2 = portA + 2
-	PA3 = portA + 3
-	PA4 = portA + 4
-	PA5 = portA + 5
-	PA6 = portA + 6
-	PA7 = portA + 7
-	PB0 = portB + 0
-	PB1 = portB + 1
-	PB2 = portB + 2
-	PB3 = portB + 3
-	PB4 = portB + 4
-	PB5 = portB + 5
-	PB6 = portB + 6
-	PB7 = portB + 7
-	PC0 = portC + 0
-	PC1 = portC + 1
-	PC2 = portC + 2
-	PC3 = portC + 3
-	PC4 = portC + 4
-	PC5 = portC + 5
-	PC6 = portC + 6
-	PC7 = portC + 7
-	PD0 = portD + 0
-	PD1 = portD + 1
-	PD2 = portD + 2
-	PD3 = portD + 3
-	PD7 = portD + 7
-	PE0 = portE + 0
-	PE1 = portE + 1
-	PE3 = portE + 3
-	PE4 = portE + 4
-	PE5 = portE + 5
-	PE6 = portE + 6
-	PF0 = portF + 0
-	PF1 = portF + 1
-	PF2 = portF + 2
-	PF3 = portF + 3
-	PF4 = portF + 4
-	PF5 = portF + 5
-	PF6 = portF + 6
-	PF7 = portF + 7
-	PG0 = portG + 0
-	PG1 = portG + 1
-	PG2 = portG + 2
-	PG5 = portG + 5
-	PH0 = portH + 0
-	PH1 = portH + 1
-	PH3 = portH + 3
-	PH4 = portH + 4
-	PH5 = portH + 5
-	PH6 = portH + 6
-	PJ0 = portJ + 0
-	PJ1 = portJ + 1
-	PK0 = portK + 0
-	PK1 = portK + 1
-	PK2 = portK + 2
-	PK3 = portK + 3
-	PK4 = portH + 4
-	PK5 = portH + 5
-	PK6 = portH + 6
-	PK7 = portH + 7
-	PL0 = portL + 0
-	PL1 = portL + 1
-	PL2 = portL + 2
-	PL3 = portL + 3
-	PL4 = portL + 4
-	PL5 = portL + 5
-	PL6 = portL + 6
-	PL7 = portL + 7
-)
-
-// getPortMask returns the PORTx register and mask for the pin.
-func (p Pin) getPortMask() (*volatile.Register8, uint8) {
-	switch {
-	case p >= PA0 && p <= PA7:
-		return avr.PORTA, 1 << uint8(p-portA)
-	case p >= PB0 && p <= PB7:
-		return avr.PORTB, 1 << uint8(p-portB)
-	case p >= PC0 && p <= PC7:
-		return avr.PORTC, 1 << uint8(p-portC)
-	case p >= PD0 && p <= PD7:
-		return avr.PORTD, 1 << uint8(p-portD)
-	case p >= PE0 && p <= PE6:
-		return avr.PORTE, 1 << uint8(p-portE)
-	case p >= PF0 && p <= PF7:
-		return avr.PORTF, 1 << uint8(p-portF)
-	case p >= PG0 && p <= PG5:
-		return avr.PORTG, 1 << uint8(p-portG)
-	case p >= PH0 && p <= PH6:
-		return avr.PORTH, 1 << uint8(p-portH)
-	case p >= PJ0 && p <= PJ1:
-		return avr.PORTJ, 1 << uint8(p-portJ)
-	case p >= PK0 && p <= PK7:
-		return avr.PORTK, 1 << uint8(p-portK)
-	case p >= PL0 && p <= PL7:
-		return avr.PORTL, 1 << uint8(p-portL)
-	default:
-		return avr.PORTA, 255
-	}
-}
-
-// PWM is one PWM peripheral, which consists of a counter and two output
-// channels (that can be connected to two fixed pins). You can set the frequency
-// using SetPeriod, but only for all the channels in this PWM peripheral at
-// once.
-type PWM struct {
-	num uint8
-}
-
-var (
-	Timer0 = PWM{0} // 8 bit timer for PB7 and PG5
-	Timer1 = PWM{1} // 16 bit timer for PB5 and PB6
-	Timer2 = PWM{2} // 8 bit timer for PB4 and PH6
-	Timer3 = PWM{3} // 16 bit timer for PE3, PE4 and PE5
-	Timer4 = PWM{4} // 16 bit timer for PH3, PH4 and PH5
-	Timer5 = PWM{5} // 16 bit timer for PL3, PL4 and PL5
-)
-
-// Configure enables and configures this PWM.
-//
-// For the two 8 bit timers, there is only a limited number of periods
-// available, namely the CPU frequency divided by 256 and again divided by 1, 8,
-// 64, 256, or 1024. For a MCU running at 16MHz, this would be a period of 16µs,
-// 128µs, 1024µs, 4096µs, or 16384µs.
-func (pwm PWM) Configure(config PWMConfig) error {
-
-	switch pwm.num {
-	case 0, 2: // 8-bit timers (Timer/counter 0 and Timer/counter 2)
-		// Calculate the timer prescaler.
-		// While we could configure a flexible top, that would sacrifice one of
-		// the PWM output compare registers and thus a PWM channel. I've chosen
-		// to instead limit this timer to a fixed number of frequencies.
-		var prescaler uint8
-		switch config.Period {
-		case 0, (uint64(1e9) * 256 * 1) / uint64(CPUFrequency()):
-			prescaler = 1
-		case (uint64(1e9) * 256 * 8) / uint64(CPUFrequency()):
-			prescaler = 2
-		case (uint64(1e9) * 256 * 64) / uint64(CPUFrequency()):
-			prescaler = 3
-		case (uint64(1e9) * 256 * 256) / uint64(CPUFrequency()):
-			prescaler = 4
-		case (uint64(1e9) * 256 * 1024) / uint64(CPUFrequency()):
-			prescaler = 5
-		default:
-			return ErrPWMPeriodTooLong
-		}
-
-		if pwm.num == 0 {
-			avr.TCCR0B.Set(prescaler)
-			// Set the PWM mode to fast PWM (mode = 3).
-			avr.TCCR0A.Set(avr.TCCR0A_WGM00 | avr.TCCR0A_WGM01)
-		} else {
-			avr.TCCR2B.Set(prescaler)
-			// Set the PWM mode to fast PWM (mode = 3).
-			avr.TCCR2A.Set(avr.TCCR2A_WGM20 | avr.TCCR2A_WGM21)
-		}
-	case 1, 3, 4, 5:
-		// The top value is the number of PWM ticks a PWM period takes. It is
-		// initially picked assuming an unlimited counter top and no PWM
-		// prescaler.
-		var top uint64
-		if config.Period == 0 {
-			// Use a top appropriate for LEDs. Picking a relatively low period
-			// here (0xff) for consistency with the other timers.
-			top = 0xff
-		} else {
-			// The formula below calculates the following formula, optimized:
-			//     top = period * (CPUFrequency() / 1e9)
-			// By dividing the CPU frequency first (an operation that is easily
-			// optimized away) the period has less chance of overflowing.
-			top = config.Period * (uint64(CPUFrequency()) / 1000000) / 1000
-		}
-
-		// The ideal PWM period may be larger than would fit in the PWM counter,
-		// which is 16 bits (see maxTop). Therefore, try to make the PWM clock
-		// speed lower with a prescaler to make the top value fit the maximum
-		// top value.
-
-		const maxTop = 0x10000
-		var prescalingTop uint8
-		switch {
-		case top <= maxTop:
-			prescalingTop = 3<<3 | 1 // no prescaling
-		case top/8 <= maxTop:
-			prescalingTop = 3<<3 | 2 // divide by 8
-			top /= 8
-		case top/64 <= maxTop:
-			prescalingTop = 3<<3 | 3 // divide by 64
-			top /= 64
-		case top/256 <= maxTop:
-			prescalingTop = 3<<3 | 4 // divide by 256
-			top /= 256
-		case top/1024 <= maxTop:
-			prescalingTop = 3<<3 | 5 // divide by 1024
-			top /= 1024
-		default:
-			return ErrPWMPeriodTooLong
-		}
-
-		// A top of 0x10000 is at 100% duty cycle. Subtract one because the
-		// counter counts from 0, not 1 (avoiding an off-by-one).
-		top -= 1
-
-		switch pwm.num {
-		case 1:
-			avr.TCCR1A.Set(avr.TCCR1A_WGM11)
-			avr.TCCR1B.Set(prescalingTop)
-			avr.ICR1H.Set(uint8(top >> 8))
-			avr.ICR1L.Set(uint8(top))
-		case 3:
-			avr.TCCR3A.Set(avr.TCCR3A_WGM31)
-			avr.TCCR3B.Set(prescalingTop)
-			avr.ICR3H.Set(uint8(top >> 8))
-			avr.ICR3L.Set(uint8(top))
-		case 4:
-			avr.TCCR4A.Set(avr.TCCR4A_WGM41)
-			avr.TCCR4B.Set(prescalingTop)
-			avr.ICR4H.Set(uint8(top >> 8))
-			avr.ICR4L.Set(uint8(top))
-		case 5:
-			avr.TCCR5A.Set(avr.TCCR5A_WGM51)
-			avr.TCCR5B.Set(prescalingTop)
-			avr.ICR5H.Set(uint8(top >> 8))
-			avr.ICR5L.Set(uint8(top))
-		}
-	}
-	return nil
-}
-
-// SetPeriod updates the period of this PWM peripheral.
-// To set a particular frequency, use the following formula:
-//
-//     period = 1e9 / frequency
-//
-// If you use a period of 0, a period that works well for LEDs will be picked.
-//
-// SetPeriod will not change the prescaler, but also won't change the current
-// value in any of the channels. This means that you may need to update the
-// value for the particular channel.
-//
-// Note that you cannot pick any arbitrary period after the PWM peripheral has
-// been configured. If you want to switch between frequencies, pick the lowest
-// frequency (longest period) once when calling Configure and adjust the
-// frequency here as needed.
-func (pwm PWM) SetPeriod(period uint64) error {
-	if pwm.num == 0 || pwm.num == 2 {
-		return ErrPWMPeriodTooLong // TODO better error message
-	}
-
-	// The top value is the number of PWM ticks a PWM period takes. It is
-	// initially picked assuming an unlimited counter top and no PWM
-	// prescaler.
-	var top uint64
-	if period == 0 {
-		// Use a top appropriate for LEDs. Picking a relatively low period
-		// here (0xff) for consistency with the other timers.
-		top = 0xff
-	} else {
-		// The formula below calculates the following formula, optimized:
-		//     top = period * (CPUFrequency() / 1e9)
-		// By dividing the CPU frequency first (an operation that is easily
-		// optimized away) the period has less chance of overflowing.
-		top = period * (uint64(CPUFrequency()) / 1000000) / 1000
-	}
-
-	var prescaler uint8
-
-	switch pwm.num {
-	case 1:
-		prescaler = avr.TCCR1B.Get() & 0x7
-	case 3:
-		prescaler = avr.TCCR3B.Get() & 0x7
-	case 4:
-		prescaler = avr.TCCR4B.Get() & 0x7
-	case 5:
-		prescaler = avr.TCCR5B.Get() & 0x7
-	}
-
-	switch prescaler {
-	case 1:
-		top /= 1
-	case 2:
-		top /= 8
-	case 3:
-		top /= 64
-	case 4:
-		top /= 256
-	case 5:
-		top /= 1024
-	}
-
-	// A top of 0x10000 is at 100% duty cycle. Subtract one because the counter
-	// counts from 0, not 1 (avoiding an off-by-one).
-	top -= 1
-
-	if top > 0xffff {
-		return ErrPWMPeriodTooLong
-	}
-
-	switch pwm.num {
-	case 1:
-		// Warning: this change is not atomic!
-		avr.ICR1H.Set(uint8(top >> 8))
-		avr.ICR1L.Set(uint8(top))
-
-		// ... and because of that, set the counter back to zero to avoid most of
-		// the effects of this non-atomicity.
-		avr.TCNT1H.Set(0)
-		avr.TCNT1L.Set(0)
-	case 3:
-		// Warning: this change is not atomic!
-		avr.ICR3H.Set(uint8(top >> 8))
-		avr.ICR3L.Set(uint8(top))
-
-		// ... and because of that, set the counter back to zero to avoid most of
-		// the effects of this non-atomicity.
-		avr.TCNT3H.Set(0)
-		avr.TCNT3L.Set(0)
-	case 4:
-		// Warning: this change is not atomic!
-		avr.ICR4H.Set(uint8(top >> 8))
-		avr.ICR4L.Set(uint8(top))
-
-		// ... and because of that, set the counter back to zero to avoid most of
-		// the effects of this non-atomicity.
-		avr.TCNT4H.Set(0)
-		avr.TCNT4L.Set(0)
-	case 5:
-		// Warning: this change is not atomic!
-		avr.ICR5H.Set(uint8(top >> 8))
-		avr.ICR5L.Set(uint8(top))
-
-		// ... and because of that, set the counter back to zero to avoid most of
-		// the effects of this non-atomicity.
-		avr.TCNT5H.Set(0)
-		avr.TCNT5L.Set(0)
-	}
-
-	return nil
-}
-
-// Top returns the current counter top, for use in duty cycle calculation. It
-// will only change with a call to Configure or SetPeriod, otherwise it is
-// constant.
-//
-// The value returned here is hardware dependent. In general, it's best to treat
-// it as an opaque value that can be divided by some number and passed to Set
-// (see Set documentation for more information).
-func (pwm PWM) Top() uint32 {
-	switch pwm.num {
-	case 1:
-		// Timer 1 has a configurable top value.
-		low := avr.ICR1L.Get()
-		high := avr.ICR1H.Get()
-		return uint32(high)<<8 | uint32(low) + 1
-	case 3:
-		// Timer 3 has a configurable top value.
-		low := avr.ICR3L.Get()
-		high := avr.ICR3H.Get()
-		return uint32(high)<<8 | uint32(low) + 1
-	case 4:
-		// Timer 4 has a configurable top value.
-		low := avr.ICR4L.Get()
-		high := avr.ICR4H.Get()
-		return uint32(high)<<8 | uint32(low) + 1
-	case 5:
-		// Timer 5 has a configurable top value.
-		low := avr.ICR5L.Get()
-		high := avr.ICR5H.Get()
-		return uint32(high)<<8 | uint32(low) + 1
-	}
-
-	// Other timers go from 0 to 0xff (0x100 or 256 in total).
-	return 256
-}
-
-// Counter returns the current counter value of the timer in this PWM
-// peripheral. It may be useful for debugging.
-func (pwm PWM) Counter() uint32 {
-	switch pwm.num {
-	case 0:
-		return uint32(avr.TCNT0.Get())
-	case 1:
-		mask := interrupt.Disable()
-		low := avr.TCNT1L.Get()
-		high := avr.TCNT1H.Get()
-		interrupt.Restore(mask)
-		return uint32(high)<<8 | uint32(low)
-	case 2:
-		return uint32(avr.TCNT2.Get())
-	case 3:
-		mask := interrupt.Disable()
-		low := avr.TCNT3L.Get()
-		high := avr.TCNT3H.Get()
-		interrupt.Restore(mask)
-		return uint32(high)<<8 | uint32(low)
-	case 4:
-		mask := interrupt.Disable()
-		low := avr.TCNT4L.Get()
-		high := avr.TCNT4H.Get()
-		interrupt.Restore(mask)
-		return uint32(high)<<8 | uint32(low)
-	case 5:
-		mask := interrupt.Disable()
-		low := avr.TCNT5L.Get()
-		high := avr.TCNT5H.Get()
-		interrupt.Restore(mask)
-		return uint32(high)<<8 | uint32(low)
-	}
-
-	// Unknown PWM.
-	return 0
-}
-
-// Period returns the used PWM period in nanoseconds. It might deviate slightly
-// from the configured period due to rounding.
-func (pwm PWM) Period() uint64 {
-	var prescaler uint8
-	switch pwm.num {
-	case 0:
-		prescaler = avr.TCCR0B.Get() & 0x7
-	case 1:
-		prescaler = avr.TCCR1B.Get() & 0x7
-	case 2:
-		prescaler = avr.TCCR2B.Get() & 0x7
-	case 3:
-		prescaler = avr.TCCR3B.Get() & 0x7
-	case 4:
-		prescaler = avr.TCCR4B.Get() & 0x7
-	case 5:
-		prescaler = avr.TCCR5B.Get() & 0x7
-	}
-	top := uint64(pwm.Top())
-	switch prescaler {
-	case 1: // prescaler 1
-		return 1 * top * 1000 / uint64(CPUFrequency()/1e6)
-	case 2: // prescaler 8
-		return 8 * top * 1000 / uint64(CPUFrequency()/1e6)
-	case 3: // prescaler 64
-		return 64 * top * 1000 / uint64(CPUFrequency()/1e6)
-	case 4: // prescaler 256
-		return 256 * top * 1000 / uint64(CPUFrequency()/1e6)
-	case 5: // prescaler 1024
-		return 1024 * top * 1000 / uint64(CPUFrequency()/1e6)
-	default: // unknown clock source
-		return 0
-	}
-}
-
-// Channel returns a PWM channel for the given pin.
-func (pwm PWM) Channel(pin Pin) (uint8, error) {
-	pin.Configure(PinConfig{Mode: PinOutput})
-	pin.Low()
-	switch pwm.num {
-	case 0:
-		switch pin {
-		case PB7: // channel A
-			avr.TCCR0A.SetBits(avr.TCCR0A_COM0A1)
-			return 0, nil
-		case PG5: // channel B
-			avr.TCCR0A.SetBits(avr.TCCR0A_COM0B1)
-			return 1, nil
-		}
-	case 1:
-		switch pin {
-		case PB5: // channel A
-			avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1)
-			return 0, nil
-		case PB6: // channel B
-			avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1)
-			return 1, nil
-		}
-	case 2:
-		switch pin {
-		case PB4: // channel A
-			avr.TCCR2A.SetBits(avr.TCCR2A_COM2A1)
-			return 0, nil
-		case PH6: // channel B
-			avr.TCCR2A.SetBits(avr.TCCR2A_COM2B1)
-			return 1, nil
-		}
-	case 3:
-		switch pin {
-		case PE3: // channel A
-			avr.TCCR3A.SetBits(avr.TCCR3A_COM3A1)
-			return 0, nil
-		case PE4: //channel B
-			avr.TCCR3A.SetBits(avr.TCCR3A_COM3B1)
-			return 1, nil
-		case PE5: //channel C
-			avr.TCCR3A.SetBits(avr.TCCR3A_COM3C1)
-			return 2, nil
-		}
-	case 4:
-		switch pin {
-		case PH3: // channel A
-			avr.TCCR4A.SetBits(avr.TCCR4A_COM4A1)
-			return 0, nil
-		case PH4: //channel B
-			avr.TCCR4A.SetBits(avr.TCCR4A_COM4B1)
-			return 1, nil
-		case PH5: //channel C
-			avr.TCCR4A.SetBits(avr.TCCR4A_COM4C1)
-			return 2, nil
-		}
-	case 5:
-		switch pin {
-		case PL3: // channel A
-			avr.TCCR5A.SetBits(avr.TCCR5A_COM5A1)
-			return 0, nil
-		case PL4: //channel B
-			avr.TCCR5A.SetBits(avr.TCCR5A_COM5B1)
-			return 1, nil
-		case PL5: //channel C
-			avr.TCCR5A.SetBits(avr.TCCR5A_COM5C1)
-			return 2, nil
-		}
-	}
-	return 0, ErrInvalidOutputPin
-}
-
-// SetInverting sets whether to invert the output of this channel.
-// Without inverting, a 25% duty cycle would mean the output is high for 25% of
-// the time and low for the rest. Inverting flips the output as if a NOT gate
-// was placed at the output, meaning that the output would be 25% low and 75%
-// high with a duty cycle of 25%.
-//
-// Note: the invert state may not be applied on the AVR until the next call to
-// ch.Set().
-func (pwm PWM) SetInverting(channel uint8, inverting bool) {
-	switch pwm.num {
-	case 0:
-		switch channel {
-		case 0: // channel A, PB7
-			if inverting {
-				avr.PORTB.SetBits(1 << 7) // PB7 high
-				avr.TCCR0A.SetBits(avr.TCCR0A_COM0A0)
-			} else {
-				avr.PORTB.ClearBits(1 << 7) // PB7 low
-				avr.TCCR0A.ClearBits(avr.TCCR0A_COM0A0)
-			}
-		case 1: // channel B, PG5
-			if inverting {
-				avr.PORTG.SetBits(1 << 5) // PG5 high
-				avr.TCCR0A.SetBits(avr.TCCR0A_COM0B0)
-			} else {
-				avr.PORTG.ClearBits(1 << 5) // PG5 low
-				avr.TCCR0A.ClearBits(avr.TCCR0A_COM0B0)
-			}
-		}
-	case 1:
-		// Note: the COM1A0/COM1B0 bit is not set with the configuration below.
-		// It will be set the following call to Set(), however.
-		switch channel {
-		case 0: // channel A, PB5
-			if inverting {
-				avr.PORTB.SetBits(1 << 5) // PB5 high
-			} else {
-				avr.PORTB.ClearBits(1 << 5) // PB5 low
-			}
-		case 1: // channel B, PB6
-			if inverting {
-				avr.PORTB.SetBits(1 << 6) // PB6 high
-			} else {
-				avr.PORTB.ClearBits(1 << 6) // PB6 low
-			}
-		}
-	case 2:
-		switch channel {
-		case 0: // channel A, PB4
-			if inverting {
-				avr.PORTB.SetBits(1 << 4) // PB4 high
-				avr.TCCR2A.SetBits(avr.TCCR2A_COM2A0)
-			} else {
-				avr.PORTB.ClearBits(1 << 4) // PB4 low
-				avr.TCCR2A.ClearBits(avr.TCCR2A_COM2A0)
-			}
-		case 1: // channel B, PH6
-			if inverting {
-				avr.PORTH.SetBits(1 << 6) // PH6 high
-				avr.TCCR2A.SetBits(avr.TCCR2A_COM2B0)
-			} else {
-				avr.PORTH.ClearBits(1 << 6) // PH6 low
-				avr.TCCR2A.ClearBits(avr.TCCR2A_COM2B0)
-			}
-		}
-	case 3:
-		// Note: the COM3A0/COM3B0 bit is not set with the configuration below.
-		// It will be set the following call to Set(), however.
-		switch channel {
-		case 0: // channel A, PE3
-			if inverting {
-				avr.PORTE.SetBits(1 << 3) // PE3 high
-			} else {
-				avr.PORTE.ClearBits(1 << 3) // PE3 low
-			}
-		case 1: // channel B, PE4
-			if inverting {
-				avr.PORTE.SetBits(1 << 4) // PE4 high
-			} else {
-				avr.PORTE.ClearBits(1 << 4) // PE4 low
-			}
-		case 2: // channel C, PE5
-			if inverting {
-				avr.PORTE.SetBits(1 << 5) // PE4 high
-			} else {
-				avr.PORTE.ClearBits(1 << 5) // PE4 low
-			}
-		}
-	case 4:
-		// Note: the COM3A0/COM3B0 bit is not set with the configuration below.
-		// It will be set the following call to Set(), however.
-		switch channel {
-		case 0: // channel A, PH3
-			if inverting {
-				avr.PORTH.SetBits(1 << 3) // PH3 high
-			} else {
-				avr.PORTH.ClearBits(1 << 3) // PH3 low
-			}
-		case 1: // channel B, PH4
-			if inverting {
-				avr.PORTH.SetBits(1 << 4) // PH4 high
-			} else {
-				avr.PORTH.ClearBits(1 << 4) // PH4 low
-			}
-		case 2: // channel C, PH5
-			if inverting {
-				avr.PORTH.SetBits(1 << 5) // PH4 high
-			} else {
-				avr.PORTH.ClearBits(1 << 5) // PH4 low
-			}
-		}
-	case 5:
-		// Note: the COM3A0/COM3B0 bit is not set with the configuration below.
-		// It will be set the following call to Set(), however.
-		switch channel {
-		case 0: // channel A, PL3
-			if inverting {
-				avr.PORTL.SetBits(1 << 3) // PL3 high
-			} else {
-				avr.PORTL.ClearBits(1 << 3) // PL3 low
-			}
-		case 1: // channel B, PL4
-			if inverting {
-				avr.PORTL.SetBits(1 << 4) // PL4 high
-			} else {
-				avr.PORTL.ClearBits(1 << 4) // PL4 low
-			}
-		case 2: // channel C, PH5
-			if inverting {
-				avr.PORTL.SetBits(1 << 5) // PL4 high
-			} else {
-				avr.PORTL.ClearBits(1 << 5) // PL4 low
-			}
-		}
-	}
-}
-
-// Set updates the channel value. This is used to control the channel duty
-// cycle, in other words the fraction of time the channel output is high (or low
-// when inverted). For example, to set it to a 25% duty cycle, use:
-//
-//     pwm.Set(channel, pwm.Top() / 4)
-//
-// pwm.Set(channel, 0) will set the output to low and pwm.Set(channel,
-// pwm.Top()) will set the output to high, assuming the output isn't inverted.
-func (pwm PWM) Set(channel uint8, value uint32) {
-	switch pwm.num {
-	case 0:
-		value := uint16(value)
-		switch channel {
-		case 0: // channel A
-			if value == 0 {
-				avr.TCCR0A.ClearBits(avr.TCCR0A_COM0A1)
-			} else {
-				avr.OCR0A.Set(uint8(value - 1))
-				avr.TCCR0A.SetBits(avr.TCCR0A_COM0A1)
-			}
-		case 1: // channel B
-			if value == 0 {
-				avr.TCCR0A.ClearBits(avr.TCCR0A_COM0B1)
-			} else {
-				avr.OCR0B.Set(uint8(value) - 1)
-				avr.TCCR0A.SetBits(avr.TCCR0A_COM0B1)
-			}
-		}
-	case 1:
-		mask := interrupt.Disable()
-		switch channel {
-		case 0: // channel A, PB5
-			if value == 0 {
-				avr.TCCR1A.ClearBits(avr.TCCR1A_COM1A1 | avr.TCCR1A_COM1A0)
-			} else {
-				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
-				avr.OCR1AH.Set(uint8(value >> 8))
-				avr.OCR1AL.Set(uint8(value))
-				if avr.PORTB.HasBits(1 << 5) { // is PB1 high?
-					// Yes, set the inverting bit.
-					avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1 | avr.TCCR1A_COM1A0)
-				} else {
-					// No, output is non-inverting.
-					avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1)
-				}
-			}
-		case 1: // channel B, PB6
-			if value == 0 {
-				avr.TCCR1A.ClearBits(avr.TCCR1A_COM1B1 | avr.TCCR1A_COM1B0)
-			} else {
-				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
-				avr.OCR1BH.Set(uint8(value >> 8))
-				avr.OCR1BL.Set(uint8(value))
-				if avr.PORTB.HasBits(1 << 6) { // is PB6 high?
-					// Yes, set the inverting bit.
-					avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1 | avr.TCCR1A_COM1B0)
-				} else {
-					// No, output is non-inverting.
-					avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1)
-				}
-			}
-		}
-		interrupt.Restore(mask)
-	case 2:
-		value := uint16(value)
-		switch channel {
-		case 0: // channel A
-			if value == 0 {
-				avr.TCCR2A.ClearBits(avr.TCCR2A_COM2A1)
-			} else {
-				avr.OCR2A.Set(uint8(value - 1))
-				avr.TCCR2A.SetBits(avr.TCCR2A_COM2A1)
-			}
-		case 1: // channel B
-			if value == 0 {
-				avr.TCCR2A.ClearBits(avr.TCCR2A_COM2B1)
-			} else {
-				avr.OCR2B.Set(uint8(value - 1))
-				avr.TCCR2A.SetBits(avr.TCCR2A_COM2B1)
-			}
-		}
-	case 3:
-		mask := interrupt.Disable()
-		switch channel {
-		case 0: // channel A, PE3
-			if value == 0 {
-				avr.TCCR3A.ClearBits(avr.TCCR3A_COM3A1 | avr.TCCR3A_COM3A0)
-			} else {
-				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
-				avr.OCR3AH.Set(uint8(value >> 8))
-				avr.OCR3AL.Set(uint8(value))
-				if avr.PORTE.HasBits(1 << 3) { // is PE3 high?
-					// Yes, set the inverting bit.
-					avr.TCCR3A.SetBits(avr.TCCR3A_COM3A1 | avr.TCCR3A_COM3A0)
-				} else {
-					// No, output is non-inverting.
-					avr.TCCR3A.SetBits(avr.TCCR3A_COM3A1)
-				}
-			}
-		case 1: // channel B, PE4
-			if value == 0 {
-				avr.TCCR3A.ClearBits(avr.TCCR3A_COM3B1 | avr.TCCR3A_COM3B0)
-			} else {
-				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
-				avr.OCR3BH.Set(uint8(value >> 8))
-				avr.OCR3BL.Set(uint8(value))
-				if avr.PORTE.HasBits(1 << 4) { // is PE4 high?
-					// Yes, set the inverting bit.
-					avr.TCCR3A.SetBits(avr.TCCR3A_COM3B1 | avr.TCCR3A_COM3B0)
-				} else {
-					// No, output is non-inverting.
-					avr.TCCR3A.SetBits(avr.TCCR3A_COM3B1)
-				}
-			}
-		case 2: // channel C, PE5
-			if value == 0 {
-				avr.TCCR3A.ClearBits(avr.TCCR3A_COM3C1 | avr.TCCR3A_COM3C0)
-			} else {
-				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
-				avr.OCR3CH.Set(uint8(value >> 8))
-				avr.OCR3CL.Set(uint8(value))
-				if avr.PORTE.HasBits(1 << 5) { // is PE5 high?
-					// Yes, set the inverting bit.
-					avr.TCCR3A.SetBits(avr.TCCR3A_COM3C1 | avr.TCCR3A_COM3C0)
-				} else {
-					// No, output is non-inverting.
-					avr.TCCR3A.SetBits(avr.TCCR3A_COM3C1)
-				}
-			}
-		}
-		interrupt.Restore(mask)
-	case 4:
-		mask := interrupt.Disable()
-		switch channel {
-		case 0: // channel A, PH3
-			if value == 0 {
-				avr.TCCR4A.ClearBits(avr.TCCR4A_COM4A1 | avr.TCCR4A_COM4A0)
-			} else {
-				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
-				avr.OCR4AH.Set(uint8(value >> 8))
-				avr.OCR4AL.Set(uint8(value))
-				if avr.PORTH.HasBits(1 << 3) { // is PH3 high?
-					// Yes, set the inverting bit.
-					avr.TCCR4A.SetBits(avr.TCCR4A_COM4A1 | avr.TCCR4A_COM4A0)
-				} else {
-					// No, output is non-inverting.
-					avr.TCCR4A.SetBits(avr.TCCR4A_COM4A1)
-				}
-			}
-		case 1: // channel B, PH4
-			if value == 0 {
-				avr.TCCR4A.ClearBits(avr.TCCR4A_COM4B1 | avr.TCCR4A_COM4B0)
-			} else {
-				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
-				avr.OCR4BH.Set(uint8(value >> 8))
-				avr.OCR4BL.Set(uint8(value))
-				if avr.PORTH.HasBits(1 << 4) { // is PH4 high?
-					// Yes, set the inverting bit.
-					avr.TCCR4A.SetBits(avr.TCCR4A_COM4B1 | avr.TCCR4A_COM4B0)
-				} else {
-					// No, output is non-inverting.
-					avr.TCCR4A.SetBits(avr.TCCR4A_COM4B1)
-				}
-			}
-		case 2: // channel C, PH5
-			if value == 0 {
-				avr.TCCR4A.ClearBits(avr.TCCR4A_COM4C1 | avr.TCCR4A_COM4C0)
-			} else {
-				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
-				avr.OCR4CH.Set(uint8(value >> 8))
-				avr.OCR4CL.Set(uint8(value))
-				if avr.PORTH.HasBits(1 << 5) { // is PH5 high?
-					// Yes, set the inverting bit.
-					avr.TCCR4A.SetBits(avr.TCCR4A_COM4C1 | avr.TCCR4A_COM4C0)
-				} else {
-					// No, output is non-inverting.
-					avr.TCCR4A.SetBits(avr.TCCR4A_COM4C1)
-				}
-			}
-		}
-		interrupt.Restore(mask)
-	case 5:
-		mask := interrupt.Disable()
-		switch channel {
-		case 0: // channel A, PL3
-			if value == 0 {
-				avr.TCCR5A.ClearBits(avr.TCCR5A_COM5A1 | avr.TCCR5A_COM5A0)
-			} else {
-				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
-				avr.OCR5AH.Set(uint8(value >> 8))
-				avr.OCR5AL.Set(uint8(value))
-				if avr.PORTL.HasBits(1 << 3) { // is PL3 high?
-					// Yes, set the inverting bit.
-					avr.TCCR5A.SetBits(avr.TCCR5A_COM5A1 | avr.TCCR5A_COM5A0)
-				} else {
-					// No, output is non-inverting.
-					avr.TCCR5A.SetBits(avr.TCCR5A_COM5A1)
-				}
-			}
-		case 1: // channel B, PL4
-			if value == 0 {
-				avr.TCCR5A.ClearBits(avr.TCCR5A_COM5B1 | avr.TCCR5A_COM5B0)
-			} else {
-				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
-				avr.OCR5BH.Set(uint8(value >> 8))
-				avr.OCR5BL.Set(uint8(value))
-				if avr.PORTL.HasBits(1 << 4) { // is PL4 high?
-					// Yes, set the inverting bit.
-					avr.TCCR5A.SetBits(avr.TCCR5A_COM5B1 | avr.TCCR5A_COM5B0)
-				} else {
-					// No, output is non-inverting.
-					avr.TCCR5A.SetBits(avr.TCCR5A_COM5B1)
-				}
-			}
-		case 2: // channel C, PL5
-			if value == 0 {
-				avr.TCCR5A.ClearBits(avr.TCCR5A_COM5C1 | avr.TCCR5A_COM5C0)
-			} else {
-				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
-				avr.OCR5CH.Set(uint8(value >> 8))
-				avr.OCR5CL.Set(uint8(value))
-				if avr.PORTL.HasBits(1 << 5) { // is PL5 high?
-					// Yes, set the inverting bit.
-					avr.TCCR5A.SetBits(avr.TCCR5A_COM5C1 | avr.TCCR5A_COM5C0)
-				} else {
-					// No, output is non-inverting.
-					avr.TCCR5A.SetBits(avr.TCCR5A_COM5C1)
-				}
-			}
-		}
-		interrupt.Restore(mask)
-	}
-}
-
-// SPI configuration
-var SPI0 = SPI{
-	spcr: avr.SPCR,
-	spdr: avr.SPDR,
-	spsr: avr.SPSR,
-	sck:  PB1,
-	sdo:  PB2,
-	sdi:  PB3,
-	cs:   PB0}
@@ -4,7 +4,6 @@ package machine

 import (
 	"device/avr"
-	"runtime/interrupt"
 	"runtime/volatile"
 )

@@ -22,432 +21,71 @@ func (p Pin) getPortMask() (*volatile.Register8, uint8) {
 	}
 }

-// PWM is one PWM peripheral, which consists of a counter and two output
-// channels (that can be connected to two fixed pins). You can set the frequency
-// using SetPeriod, but only for all the channels in this PWM peripheral at
-// once.
-type PWM struct {
-	num uint8
+// InitPWM initializes the registers needed for PWM.
+func InitPWM() {
+	// use waveform generation
+	avr.TCCR0A.SetBits(avr.TCCR0A_WGM00)
+
+	// set timer 0 prescale factor to 64
+	avr.TCCR0B.SetBits(avr.TCCR0B_CS01 | avr.TCCR0B_CS00)
+
+	// set timer 1 prescale factor to 64
+	avr.TCCR1B.SetBits(avr.TCCR1B_CS11)
+
+	// put timer 1 in 8-bit phase correct pwm mode
+	avr.TCCR1A.SetBits(avr.TCCR1A_WGM10)
+
+	// set timer 2 prescale factor to 64
+	avr.TCCR2B.SetBits(avr.TCCR2B_CS22)
+
+	// configure timer 2 for phase correct pwm (8-bit)
+	avr.TCCR2A.SetBits(avr.TCCR2A_WGM20)
 }

-var (
-	Timer0 = PWM{0} // 8 bit timer for PD5 and PD6
-	Timer1 = PWM{1} // 16 bit timer for PB1 and PB2
-	Timer2 = PWM{2} // 8 bit timer for PB3 and PD3
-)
-
-// Configure enables and configures this PWM.
-//
-// For the two 8 bit timers, there is only a limited number of periods
-// available, namely the CPU frequency divided by 256 and again divided by 1, 8,
-// 64, 256, or 1024. For a MCU running at 16MHz, this would be a period of 16µs,
-// 128µs, 1024µs, 4096µs, or 16384µs.
-func (pwm PWM) Configure(config PWMConfig) error {
-	switch pwm.num {
-	case 0, 2: // 8-bit timers (Timer/counter 0 and Timer/counter 2)
-		// Calculate the timer prescaler.
-		// While we could configure a flexible top, that would sacrifice one of
-		// the PWM output compare registers and thus a PWM channel. I've chosen
-		// to instead limit this timer to a fixed number of frequencies.
-		var prescaler uint8
-		switch config.Period {
-		case 0, (uint64(1e9) * 256 * 1) / uint64(CPUFrequency()):
-			prescaler = 1
-		case (uint64(1e9) * 256 * 8) / uint64(CPUFrequency()):
-			prescaler = 2
-		case (uint64(1e9) * 256 * 64) / uint64(CPUFrequency()):
-			prescaler = 3
-		case (uint64(1e9) * 256 * 256) / uint64(CPUFrequency()):
-			prescaler = 4
-		case (uint64(1e9) * 256 * 1024) / uint64(CPUFrequency()):
-			prescaler = 5
-		default:
-			return ErrPWMPeriodTooLong
-		}
-
-		if pwm.num == 0 {
-			avr.TCCR0B.Set(prescaler)
-			// Set the PWM mode to fast PWM (mode = 3).
-			avr.TCCR0A.Set(avr.TCCR0A_WGM00 | avr.TCCR0A_WGM01)
-		} else {
-			avr.TCCR2B.Set(prescaler)
-			// Set the PWM mode to fast PWM (mode = 3).
-			avr.TCCR2A.Set(avr.TCCR2A_WGM20 | avr.TCCR2A_WGM21)
-		}
-	case 1: // Timer/counter 1
-		// The top value is the number of PWM ticks a PWM period takes. It is
-		// initially picked assuming an unlimited counter top and no PWM
-		// prescaler.
-		var top uint64
-		if config.Period == 0 {
-			// Use a top appropriate for LEDs. Picking a relatively low period
-			// here (0xff) for consistency with the other timers.
-			top = 0xff
-		} else {
-			// The formula below calculates the following formula, optimized:
-			//     top = period * (CPUFrequency() / 1e9)
-			// By dividing the CPU frequency first (an operation that is easily
-			// optimized away) the period has less chance of overflowing.
-			top = config.Period * (uint64(CPUFrequency()) / 1000000) / 1000
-		}
-
-		avr.TCCR1A.Set(avr.TCCR1A_WGM11)
-
-		// The ideal PWM period may be larger than would fit in the PWM counter,
-		// which is 16 bits (see maxTop). Therefore, try to make the PWM clock
-		// speed lower with a prescaler to make the top value fit the maximum
-		// top value.
-		const maxTop = 0x10000
-		switch {
-		case top <= maxTop:
-			avr.TCCR1B.Set(3<<3 | 1) // no prescaling
-		case top/8 <= maxTop:
-			avr.TCCR1B.Set(3<<3 | 2) // divide by 8
-			top /= 8
-		case top/64 <= maxTop:
-			avr.TCCR1B.Set(3<<3 | 3) // divide by 64
-			top /= 64
-		case top/256 <= maxTop:
-			avr.TCCR1B.Set(3<<3 | 4) // divide by 256
-			top /= 256
-		case top/1024 <= maxTop:
-			avr.TCCR1B.Set(3<<3 | 5) // divide by 1024
-			top /= 1024
-		default:
-			return ErrPWMPeriodTooLong
-		}
-
-		// A top of 0x10000 is at 100% duty cycle. Subtract one because the
-		// counter counts from 0, not 1 (avoiding an off-by-one).
-		top -= 1
-
-		avr.ICR1H.Set(uint8(top >> 8))
-		avr.ICR1L.Set(uint8(top))
+// Configure configures a PWM pin for output.
+func (pwm PWM) Configure() error {
+	switch pwm.Pin / 8 {
+	case 0: // port B
+		avr.DDRB.SetBits(1 << uint8(pwm.Pin))
+	case 2: // port D
+		avr.DDRD.SetBits(1 << uint8(pwm.Pin-16))
 	}
 	return nil
 }

-// SetPeriod updates the period of this PWM peripheral.
-// To set a particular frequency, use the following formula:
-//
-//     period = 1e9 / frequency
-//
-// If you use a period of 0, a period that works well for LEDs will be picked.
-//
-// SetPeriod will not change the prescaler, but also won't change the current
-// value in any of the channels. This means that you may need to update the
-// value for the particular channel.
-//
-// Note that you cannot pick any arbitrary period after the PWM peripheral has
-// been configured. If you want to switch between frequencies, pick the lowest
-// frequency (longest period) once when calling Configure and adjust the
-// frequency here as needed.
-func (pwm PWM) SetPeriod(period uint64) error {
-	if pwm.num != 1 {
-		return ErrPWMPeriodTooLong // TODO better error message
-	}
-
-	// The top value is the number of PWM ticks a PWM period takes. It is
-	// initially picked assuming an unlimited counter top and no PWM
-	// prescaler.
-	var top uint64
-	if period == 0 {
-		// Use a top appropriate for LEDs. Picking a relatively low period
-		// here (0xff) for consistency with the other timers.
-		top = 0xff
-	} else {
-		// The formula below calculates the following formula, optimized:
-		//     top = period * (CPUFrequency() / 1e9)
-		// By dividing the CPU frequency first (an operation that is easily
-		// optimized away) the period has less chance of overflowing.
-		top = period * (uint64(CPUFrequency()) / 1000000) / 1000
-	}
-
-	prescaler := avr.TCCR1B.Get() & 0x7
-	switch prescaler {
-	case 1:
-		top /= 1
-	case 2:
-		top /= 8
-	case 3:
-		top /= 64
-	case 4:
-		top /= 256
-	case 5:
-		top /= 1024
-	}
-
-	// A top of 0x10000 is at 100% duty cycle. Subtract one because the counter
-	// counts from 0, not 1 (avoiding an off-by-one).
-	top -= 1
-
-	if top > 0xffff {
-		return ErrPWMPeriodTooLong
-	}
-
-	// Warning: this change is not atomic!
-	avr.ICR1H.Set(uint8(top >> 8))
-	avr.ICR1L.Set(uint8(top))
-
-	// ... and because of that, set the counter back to zero to avoid most of
-	// the effects of this non-atomicity.
-	avr.TCNT1H.Set(0)
-	avr.TCNT1L.Set(0)
-
-	return nil
-}
-
-// Top returns the current counter top, for use in duty cycle calculation. It
-// will only change with a call to Configure or SetPeriod, otherwise it is
-// constant.
-//
-// The value returned here is hardware dependent. In general, it's best to treat
-// it as an opaque value that can be divided by some number and passed to Set
-// (see Set documentation for more information).
-func (pwm PWM) Top() uint32 {
-	if pwm.num == 1 {
-		// Timer 1 has a configurable top value.
-		low := avr.ICR1L.Get()
-		high := avr.ICR1H.Get()
-		return uint32(high)<<8 | uint32(low) + 1
-	}
-	// Other timers go from 0 to 0xff (0x100 or 256 in total).
-	return 256
-}
-
-// Counter returns the current counter value of the timer in this PWM
-// peripheral. It may be useful for debugging.
-func (pwm PWM) Counter() uint32 {
-	switch pwm.num {
-	case 0:
-		return uint32(avr.TCNT0.Get())
-	case 1:
-		mask := interrupt.Disable()
-		low := avr.TCNT1L.Get()
-		high := avr.TCNT1H.Get()
-		interrupt.Restore(mask)
-		return uint32(high)<<8 | uint32(low)
-	case 2:
-		return uint32(avr.TCNT2.Get())
-	}
-	// Unknown PWM.
-	return 0
-}
-
-// Period returns the used PWM period in nanoseconds. It might deviate slightly
-// from the configured period due to rounding.
-func (pwm PWM) Period() uint64 {
-	var prescaler uint8
-	switch pwm.num {
-	case 0:
-		prescaler = avr.TCCR0B.Get() & 0x7
-	case 1:
-		prescaler = avr.TCCR1B.Get() & 0x7
-	case 2:
-		prescaler = avr.TCCR2B.Get() & 0x7
-	}
-	top := uint64(pwm.Top())
-	switch prescaler {
-	case 1: // prescaler 1
-		return 1 * top * 1000 / uint64(CPUFrequency()/1e6)
-	case 2: // prescaler 8
-		return 8 * top * 1000 / uint64(CPUFrequency()/1e6)
-	case 3: // prescaler 64
-		return 64 * top * 1000 / uint64(CPUFrequency()/1e6)
-	case 4: // prescaler 256
-		return 256 * top * 1000 / uint64(CPUFrequency()/1e6)
-	case 5: // prescaler 1024
-		return 1024 * top * 1000 / uint64(CPUFrequency()/1e6)
-	default: // unknown clock source
-		return 0
-	}
-}
-
-// Channel returns a PWM channel for the given pin.
-func (pwm PWM) Channel(pin Pin) (uint8, error) {
-	pin.Configure(PinConfig{Mode: PinOutput})
-	pin.Low()
-	switch pwm.num {
-	case 0:
-		switch pin {
-		case PD6: // channel A
-			avr.TCCR0A.SetBits(avr.TCCR0A_COM0A1)
-			return 0, nil
-		case PD5: // channel B
-			avr.TCCR0A.SetBits(avr.TCCR0A_COM0B1)
-			return 1, nil
-		}
-	case 1:
-		switch pin {
-		case PB1: // channel A
-			avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1)
-			return 0, nil
-		case PB2: // channel B
-			avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1)
-			return 1, nil
-		}
-	case 2:
-		switch pin {
-		case PB3: // channel A
-			avr.TCCR2A.SetBits(avr.TCCR2A_COM2A1)
-			return 0, nil
-		case PD3: // channel B
-			avr.TCCR2A.SetBits(avr.TCCR2A_COM2B1)
-			return 1, nil
-		}
-	}
-	return 0, ErrInvalidOutputPin
-}
-
-// SetInverting sets whether to invert the output of this channel.
-// Without inverting, a 25% duty cycle would mean the output is high for 25% of
-// the time and low for the rest. Inverting flips the output as if a NOT gate
-// was placed at the output, meaning that the output would be 25% low and 75%
-// high with a duty cycle of 25%.
-//
-// Note: the invert state may not be applied on the AVR until the next call to
-// ch.Set().
-func (pwm PWM) SetInverting(channel uint8, inverting bool) {
-	switch pwm.num {
-	case 0:
-		switch channel {
-		case 0: // channel A
-			if inverting {
-				avr.PORTB.SetBits(1 << 6) // PB6 high
-				avr.TCCR0A.SetBits(avr.TCCR0A_COM0A0)
-			} else {
-				avr.PORTB.ClearBits(1 << 6) // PB6 low
-				avr.TCCR0A.ClearBits(avr.TCCR0A_COM0A0)
-			}
-		case 1: // channel B
-			if inverting {
-				avr.PORTB.SetBits(1 << 5) // PB5 high
-				avr.TCCR0A.SetBits(avr.TCCR0A_COM0B0)
-			} else {
-				avr.PORTB.ClearBits(1 << 5) // PB5 low
-				avr.TCCR0A.ClearBits(avr.TCCR0A_COM0B0)
-			}
-		}
-	case 1:
-		// Note: the COM1A0/COM1B0 bit is not set with the configuration below.
-		// It will be set the following call to Set(), however.
-		switch channel {
-		case 0: // channel A, PB1
-			if inverting {
-				avr.PORTB.SetBits(1 << 1) // PB1 high
-			} else {
-				avr.PORTB.ClearBits(1 << 1) // PB1 low
-			}
-		case 1: // channel B, PB2
-			if inverting {
-				avr.PORTB.SetBits(1 << 2) // PB2 high
-			} else {
-				avr.PORTB.ClearBits(1 << 2) // PB2 low
-			}
-		}
-	case 2:
-		switch channel {
-		case 0: // channel A
-			if inverting {
-				avr.PORTB.SetBits(1 << 3) // PB3 high
-				avr.TCCR2A.SetBits(avr.TCCR2A_COM2A0)
-			} else {
-				avr.PORTB.ClearBits(1 << 3) // PB3 low
-				avr.TCCR2A.ClearBits(avr.TCCR2A_COM2A0)
-			}
-		case 1: // channel B
-			if inverting {
-				avr.PORTD.SetBits(1 << 3) // PD3 high
-				avr.TCCR2A.SetBits(avr.TCCR2A_COM2B0)
-			} else {
-				avr.PORTD.ClearBits(1 << 3) // PD3 low
-				avr.TCCR2A.ClearBits(avr.TCCR2A_COM2B0)
-			}
-		}
-	}
-}
-
-// Set updates the channel value. This is used to control the channel duty
-// cycle, in other words the fraction of time the channel output is high (or low
-// when inverted). For example, to set it to a 25% duty cycle, use:
-//
-//     pwm.Set(channel, pwm.Top() / 4)
-//
-// pwm.Set(channel, 0) will set the output to low and pwm.Set(channel,
-// pwm.Top()) will set the output to high, assuming the output isn't inverted.
-func (pwm PWM) Set(channel uint8, value uint32) {
-	switch pwm.num {
-	case 0:
-		value := uint16(value)
-		switch channel {
-		case 0: // channel A
-			if value == 0 {
-				avr.TCCR0A.ClearBits(avr.TCCR0A_COM0A1)
-			} else {
-				avr.OCR0A.Set(uint8(value - 1))
-				avr.TCCR0A.SetBits(avr.TCCR0A_COM0A1)
-			}
-		case 1: // channel B
-			if value == 0 {
-				avr.TCCR0A.ClearBits(avr.TCCR0A_COM0B1)
-			} else {
-				avr.OCR0B.Set(uint8(value) - 1)
-				avr.TCCR0A.SetBits(avr.TCCR0A_COM0B1)
-			}
-		}
-	case 1:
-		mask := interrupt.Disable()
-		switch channel {
-		case 0: // channel A, PB1
-			if value == 0 {
-				avr.TCCR1A.ClearBits(avr.TCCR1A_COM1A1 | avr.TCCR1A_COM1A0)
-			} else {
-				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
-				avr.OCR1AH.Set(uint8(value >> 8))
-				avr.OCR1AL.Set(uint8(value))
-				if avr.PORTB.HasBits(1 << 1) { // is PB1 high?
-					// Yes, set the inverting bit.
-					avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1 | avr.TCCR1A_COM1A0)
-				} else {
-					// No, output is non-inverting.
-					avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1)
-				}
-			}
-		case 1: // channel B, PB2
-			if value == 0 {
-				avr.TCCR1A.ClearBits(avr.TCCR1A_COM1B1 | avr.TCCR1A_COM1B0)
-			} else {
-				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
-				avr.OCR1BH.Set(uint8(value >> 8))
-				avr.OCR1BL.Set(uint8(value))
-				if avr.PORTB.HasBits(1 << 2) { // is PB2 high?
-					// Yes, set the inverting bit.
-					avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1 | avr.TCCR1A_COM1B0)
-				} else {
-					// No, output is non-inverting.
-					avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1)
-				}
-			}
-		}
-		interrupt.Restore(mask)
-	case 2:
-		value := uint16(value)
-		switch channel {
-		case 0: // channel A
-			if value == 0 {
-				avr.TCCR2A.ClearBits(avr.TCCR2A_COM2A1)
-			} else {
-				avr.OCR2A.Set(uint8(value - 1))
-				avr.TCCR2A.SetBits(avr.TCCR2A_COM2A1)
-			}
-		case 1: // channel B
-			if value == 0 {
-				avr.TCCR2A.ClearBits(avr.TCCR2A_COM2B1)
-			} else {
-				avr.OCR2B.Set(uint8(value - 1))
-				avr.TCCR2A.SetBits(avr.TCCR2A_COM2B1)
-			}
-		}
+// Set turns on the duty cycle for a PWM pin using the provided value. On the AVR this is normally a
+// 8-bit value ranging from 0 to 255.
+func (pwm PWM) Set(value uint16) {
+	value8 := uint8(value >> 8)
+	switch pwm.Pin {
+	case PD3:
+		// connect pwm to pin on timer 2, channel B
+		avr.TCCR2A.SetBits(avr.TCCR2A_COM2B1)
+		avr.OCR2B.Set(value8) // set pwm duty
+	case PD5:
+		// connect pwm to pin on timer 0, channel B
+		avr.TCCR0A.SetBits(avr.TCCR0A_COM0B1)
+		avr.OCR0B.Set(value8) // set pwm duty
+	case PD6:
+		// connect pwm to pin on timer 0, channel A
+		avr.TCCR0A.SetBits(avr.TCCR0A_COM0A1)
+		avr.OCR0A.Set(value8) // set pwm duty
+	case PB1:
+		// connect pwm to pin on timer 1, channel A
+		avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1)
+		// this is a 16-bit value, but we only currently allow the low order bits to be set
+		avr.OCR1AL.Set(value8) // set pwm duty
+	case PB2:
+		// connect pwm to pin on timer 1, channel B
+		avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1)
+		// this is a 16-bit value, but we only currently allow the low order bits to be set
+		avr.OCR1BL.Set(value8) // set pwm duty
+	case PB3:
+		// connect pwm to pin on timer 2, channel A
+		avr.TCCR2A.SetBits(avr.TCCR2A_COM2A1)
+		avr.OCR2A.Set(value8) // set pwm duty
+	default:
+		panic("Invalid PWM pin")
 	}
 }

@@ -8,6 +8,7 @@
 package machine

 import (
+	"device"
 	"device/arm"
 	"device/sam"
 	"errors"
@@ -16,6 +17,8 @@ import (
 	"unsafe"
 )

+type PinMode uint8
+
 const (
 	PinAnalog    PinMode = 1
 	PinSERCOM    PinMode = 2
@@ -28,8 +31,8 @@ const (
 	PinInput         PinMode = 9
 	PinInputPullup   PinMode = 10
 	PinOutput        PinMode = 11
-	PinTCC           PinMode = PinTimer
-	PinTCCAlt        PinMode = PinTimerAlt
+	PinPWM           PinMode = PinTimer
+	PinPWMAlt        PinMode = PinTimerAlt
 	PinInputPulldown PinMode = 12
 )

@@ -430,18 +433,7 @@ func (a ADC) Get() uint16 {
 	sam.ADC.CTRLA.ClearBits(sam.ADC_CTRLA_ENABLE)
 	waitADCSync()

-	// scales to 16-bit result
-	switch (sam.ADC.CTRLB.Get() & sam.ADC_CTRLB_RESSEL_Msk) >> sam.ADC_CTRLB_RESSEL_Pos {
-	case sam.ADC_CTRLB_RESSEL_8BIT:
-		val = val << 8
-	case sam.ADC_CTRLB_RESSEL_10BIT:
-		val = val << 6
-	case sam.ADC_CTRLB_RESSEL_16BIT:
-		val = val << 4
-	case sam.ADC_CTRLB_RESSEL_12BIT:
-		val = val << 4
-	}
-	return val
+	return uint16(val) << 4 // scales from 12 to 16-bit result
 }

 func (a ADC) getADCChannel() uint8 {
@@ -1298,21 +1290,43 @@ var (
 // 		spi.Tx(nil, rx)
 //
 func (spi SPI) Tx(w, r []byte) error {
-	switch {
-	case w == nil:
-		// read only, so write zero and read a result.
-		spi.rx(r)
-	case r == nil:
-		// write only
-		spi.tx(w)
+	if spi.Bus.BAUD.Get() == 0x00 {
+		// When the SPI Freq is 24MHz, special processing is performed to improve the speed.

-	default:
-		// write/read
-		if len(w) != len(r) {
-			return ErrTxInvalidSliceSize
+		switch {
+		case w == nil:
+			// read only, so write zero and read a result.
+			spi.rx(r)
+		case r == nil:
+			// write only
+			spi.tx24mhz(w)
+
+		default:
+			// write/read
+			if len(w) != len(r) {
+				return ErrTxInvalidSliceSize
+			}
+
+			spi.txrx24mhz(w, r)
 		}

-		spi.txrx(w, r)
+	} else {
+		switch {
+		case w == nil:
+			// read only, so write zero and read a result.
+			spi.rx(r)
+		case r == nil:
+			// write only
+			spi.tx(w)
+
+		default:
+			// write/read
+			if len(w) != len(r) {
+				return ErrTxInvalidSliceSize
+			}
+
+			spi.txrx(w, r)
+		}
 	}

 	return nil
@@ -1365,373 +1379,243 @@ func (spi SPI) txrx(tx, rx []byte) {
 	rx[len(rx)-1] = byte(spi.Bus.DATA.Get())
 }

-// TCC is one timer/counter peripheral, which consists of a counter and multiple
-// output channels (that can be connected to actual pins). You can set the
-// frequency using SetPeriod, but only for all the channels in this TCC
-// peripheral at once.
-type TCC sam.TCC_Type
+// tx24mhz is a special tx/rx function for CPU Clock 48 Mhz and SPI Freq 24 Mhz
+func (spi SPI) tx24mhz(tx []byte) {
+	spi.Bus.DATA.Set(uint32(tx[0]))
+	device.Asm("nop")
+	device.Asm("nop")
+	device.Asm("nop")
+	device.Asm("nop")
+	device.Asm("nop")
+	device.Asm("nop")

-// The SAM D21 has three TCC peripherals, which have PWM as one feature.
-var (
-	TCC0 = (*TCC)(sam.TCC0)
-	TCC1 = (*TCC)(sam.TCC1)
-	TCC2 = (*TCC)(sam.TCC2)
-)
-
-//go:inline
-func (tcc *TCC) timer() *sam.TCC_Type {
-	return (*sam.TCC_Type)(tcc)
+	for i := 1; i < len(tx); i++ {
+		spi.Bus.DATA.Set(uint32(tx[i]))
+		device.Asm("nop")
+		device.Asm("nop")
+		spi.Bus.DATA.Get()
+	}
+	for !spi.Bus.INTFLAG.HasBits(sam.SERCOM_SPI_INTFLAG_RXC) {
+	}
+	spi.Bus.DATA.Get()
 }

-// Configure enables and configures this TCC.
-func (tcc *TCC) Configure(config PWMConfig) error {
-	// Enable the clock source for this timer.
-	switch tcc.timer() {
-	case sam.TCC0:
-		sam.PM.APBCMASK.SetBits(sam.PM_APBCMASK_TCC0_)
-		// Use GCLK0 for TCC0/TCC1
-		sam.GCLK.CLKCTRL.Set((sam.GCLK_CLKCTRL_ID_TCC0_TCC1 << sam.GCLK_CLKCTRL_ID_Pos) |
-			(sam.GCLK_CLKCTRL_GEN_GCLK0 << sam.GCLK_CLKCTRL_GEN_Pos) |
-			sam.GCLK_CLKCTRL_CLKEN)
-		for sam.GCLK.STATUS.HasBits(sam.GCLK_STATUS_SYNCBUSY) {
-		}
-	case sam.TCC1:
-		sam.PM.APBCMASK.SetBits(sam.PM_APBCMASK_TCC1_)
-		// Use GCLK0 for TCC0/TCC1
-		sam.GCLK.CLKCTRL.Set((sam.GCLK_CLKCTRL_ID_TCC0_TCC1 << sam.GCLK_CLKCTRL_ID_Pos) |
-			(sam.GCLK_CLKCTRL_GEN_GCLK0 << sam.GCLK_CLKCTRL_GEN_Pos) |
-			sam.GCLK_CLKCTRL_CLKEN)
-		for sam.GCLK.STATUS.HasBits(sam.GCLK_STATUS_SYNCBUSY) {
-		}
-	case sam.TCC2:
-		sam.PM.APBCMASK.SetBits(sam.PM_APBCMASK_TCC2_)
-		// Use GCLK0 for TCC2/TC3
-		sam.GCLK.CLKCTRL.Set((sam.GCLK_CLKCTRL_ID_TCC2_TC3 << sam.GCLK_CLKCTRL_ID_Pos) |
-			(sam.GCLK_CLKCTRL_GEN_GCLK0 << sam.GCLK_CLKCTRL_GEN_Pos) |
-			sam.GCLK_CLKCTRL_CLKEN)
-		for sam.GCLK.STATUS.HasBits(sam.GCLK_STATUS_SYNCBUSY) {
-		}
+// txrx24mhz is a special tx/rx function for CPU Clock 48 Mhz and SPI Freq 24 Mhz
+func (spi SPI) txrx24mhz(tx, rx []byte) {
+	spi.Bus.DATA.Set(uint32(tx[0]))
+	device.Asm("nop")
+	device.Asm("nop")
+	device.Asm("nop")
+	device.Asm("nop")
+	device.Asm("nop")
+	device.Asm("nop")
+
+	for i := 1; i < len(rx); i++ {
+		spi.Bus.DATA.Set(uint32(tx[i]))
+		device.Asm("nop")
+		device.Asm("nop")
+		rx[i-1] = byte(spi.Bus.DATA.Get())
+	}
+	for !spi.Bus.INTFLAG.HasBits(sam.SERCOM_SPI_INTFLAG_RXC) {
+	}
+	rx[len(rx)-1] = byte(spi.Bus.DATA.Get())
+}
+
+// PWM
+const period = 0xFFFF
+
+// InitPWM initializes the PWM interface.
+func InitPWM() {
+	// turn on timer clocks used for PWM
+	sam.PM.APBCMASK.SetBits(sam.PM_APBCMASK_TCC0_ | sam.PM_APBCMASK_TCC1_ | sam.PM_APBCMASK_TCC2_)
+
+	// Use GCLK0 for TCC0/TCC1
+	sam.GCLK.CLKCTRL.Set((sam.GCLK_CLKCTRL_ID_TCC0_TCC1 << sam.GCLK_CLKCTRL_ID_Pos) |
+		(sam.GCLK_CLKCTRL_GEN_GCLK0 << sam.GCLK_CLKCTRL_GEN_Pos) |
+		sam.GCLK_CLKCTRL_CLKEN)
+	for sam.GCLK.STATUS.HasBits(sam.GCLK_STATUS_SYNCBUSY) {
 	}

-	// Disable timer (if it was enabled). This is necessary because
-	// tcc.setPeriod may want to change the prescaler bits in CTRLA, which is
-	// only allowed when the TCC is disabled.
-	tcc.timer().CTRLA.ClearBits(sam.TCC_CTRLA_ENABLE)
+	// Use GCLK0 for TCC2/TC3
+	sam.GCLK.CLKCTRL.Set((sam.GCLK_CLKCTRL_ID_TCC2_TC3 << sam.GCLK_CLKCTRL_ID_Pos) |
+		(sam.GCLK_CLKCTRL_GEN_GCLK0 << sam.GCLK_CLKCTRL_GEN_Pos) |
+		sam.GCLK_CLKCTRL_CLKEN)
+	for sam.GCLK.STATUS.HasBits(sam.GCLK_STATUS_SYNCBUSY) {
+	}
+}
+
+// Configure configures a PWM pin for output.
+func (pwm PWM) Configure() error {
+	// figure out which TCCX timer for this pin
+	timer := pwm.getTimer()
+	if timer == nil {
+		return ErrInvalidOutputPin
+	}
+
+	// disable timer
+	timer.CTRLA.ClearBits(sam.TCC_CTRLA_ENABLE)
+	// Wait for synchronization
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_ENABLE) {
+	}

 	// Use "Normal PWM" (single-slope PWM)
-	tcc.timer().WAVE.Set(sam.TCC_WAVE_WAVEGEN_NPWM)
-
-	// Wait for synchronization of all changed registers.
-	for tcc.timer().SYNCBUSY.Get() != 0 {
+	timer.WAVE.SetBits(sam.TCC_WAVE_WAVEGEN_NPWM)
+	// Wait for synchronization
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_WAVE) {
 	}

-	// Set the period and prescaler.
-	err := tcc.setPeriod(config.Period, true)
-
-	// Enable the timer.
-	tcc.timer().CTRLA.SetBits(sam.TCC_CTRLA_ENABLE)
-
-	// Wait for synchronization of all changed registers.
-	for tcc.timer().SYNCBUSY.Get() != 0 {
+	// Set the period (the number to count to (TOP) before resetting timer)
+	//TCC0->PER.reg = period;
+	timer.PER.Set(period)
+	// Wait for synchronization
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_PER) {
 	}

-	// Return any error that might have occured in the tcc.setPeriod call.
-	return err
-}
+	// Set pin as output
+	sam.PORT.DIRSET0.Set(1 << uint8(pwm.Pin))
+	// Set pin to low
+	sam.PORT.OUTCLR0.Set(1 << uint8(pwm.Pin))

-// SetPeriod updates the period of this TCC peripheral.
-// To set a particular frequency, use the following formula:
-//
-//     period = 1e9 / frequency
-//
-// If you use a period of 0, a period that works well for LEDs will be picked.
-//
-// SetPeriod will not change the prescaler, but also won't change the current
-// value in any of the channels. This means that you may need to update the
-// value for the particular channel.
-//
-// Note that you cannot pick any arbitrary period after the TCC peripheral has
-// been configured. If you want to switch between frequencies, pick the lowest
-// frequency (longest period) once when calling Configure and adjust the
-// frequency here as needed.
-func (tcc *TCC) SetPeriod(period uint64) error {
-	err := tcc.setPeriod(period, false)
-	if err == nil {
-		if tcc.Counter() >= tcc.Top() {
-			// When setting the timer to a shorter period, there is a chance
-			// that it passes the counter value and thus goes all the way to MAX
-			// before wrapping back to zero.
-			// To avoid this, reset the counter back to 0.
-			tcc.timer().COUNT.Set(0)
-		}
+	// Enable the port multiplexer for pin
+	pwm.setPinCfg(sam.PORT_PINCFG0_PMUXEN)
+
+	// Connect TCCX timer to pin.
+	// we normally use the F channel aka ALT
+	pwmConfig := PinPWMAlt
+
+	// in the case of PA6 or PA7 we have to use E channel
+	if pwm.Pin == 6 || pwm.Pin == 7 {
+		pwmConfig = PinPWM
 	}
-	return err
-}

-// setPeriod sets the period of this TCC, possibly updating the prescaler as
-// well. The prescaler can only modified when the TCC is disabled, that is, in
-// the Configure function.
-func (tcc *TCC) setPeriod(period uint64, updatePrescaler bool) error {
-	var top uint64
-	if period == 0 {
-		// Make sure the TOP value is at 0xffff (enough for a 16-bit timer).
-		top = 0xffff
+	if pwm.Pin&1 > 0 {
+		// odd pin, so save the even pins
+		val := pwm.getPMux() & sam.PORT_PMUX0_PMUXE_Msk
+		pwm.setPMux(val | uint8(pwmConfig<<sam.PORT_PMUX0_PMUXO_Pos))
 	} else {
-		// The formula below calculates the following formula, optimized:
-		//     period * (48e6 / 1e9)
-		// This assumes that the chip is running at the (default) 48MHz speed.
-		top = period * 6 / 125
-	}
-
-	maxTop := uint64(0xffffff)
-	if tcc.timer() == sam.TCC2 {
-		// TCC2 is a 16-bit timer, not a 24-bit timer.
-		maxTop = 0xffff
-	}
-
-	if updatePrescaler {
-		// This function was called during Configure(), with the timer disabled.
-		// Note that updating the prescaler can only happen while the peripheral
-		// is disabled.
-		var prescaler uint32
-		switch {
-		case top <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV1
-		case top/2 <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV2
-			top = top / 2
-		case top/4 <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV4
-			top = top / 4
-		case top/8 <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV8
-			top = top / 8
-		case top/16 <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV16
-			top = top / 16
-		case top/64 <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV64
-			top = top / 64
-		case top/256 <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV256
-			top = top / 256
-		case top/1024 <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV1024
-			top = top / 1024
-		default:
-			return ErrPWMPeriodTooLong
-		}
-		tcc.timer().CTRLA.Set((tcc.timer().CTRLA.Get() &^ sam.TCC_CTRLA_PRESCALER_Msk) | (prescaler << sam.TCC_CTRLA_PRESCALER_Pos))
-	} else {
-		// Do not update the prescaler, but use the already-configured
-		// prescaler. This is the normal SetPeriod case, where the prescaler
-		// must not be changed.
-		prescaler := (tcc.timer().CTRLA.Get() & sam.TCC_CTRLA_PRESCALER_Msk) >> sam.TCC_CTRLA_PRESCALER_Pos
-		switch prescaler {
-		case sam.TCC_CTRLA_PRESCALER_DIV1:
-			top /= 1 // no-op
-		case sam.TCC_CTRLA_PRESCALER_DIV2:
-			top /= 2
-		case sam.TCC_CTRLA_PRESCALER_DIV4:
-			top /= 4
-		case sam.TCC_CTRLA_PRESCALER_DIV8:
-			top /= 8
-		case sam.TCC_CTRLA_PRESCALER_DIV16:
-			top /= 16
-		case sam.TCC_CTRLA_PRESCALER_DIV64:
-			top /= 64
-		case sam.TCC_CTRLA_PRESCALER_DIV256:
-			top /= 256
-		case sam.TCC_CTRLA_PRESCALER_DIV1024:
-			top /= 1024
-		default:
-			// unreachable
-		}
-		if top > maxTop {
-			return ErrPWMPeriodTooLong
-		}
-	}
-
-	// Set the period (the counter top).
-	tcc.timer().PER.Set(uint32(top) - 1)
-
-	// Wait for synchronization of CTRLA.PRESCALER and PER registers.
-	for tcc.timer().SYNCBUSY.Get() != 0 {
+		// even pin, so save the odd pins
+		val := pwm.getPMux() & sam.PORT_PMUX0_PMUXO_Msk
+		pwm.setPMux(val | uint8(pwmConfig<<sam.PORT_PMUX0_PMUXE_Pos))
 	}

 	return nil
 }

-// Top returns the current counter top, for use in duty cycle calculation. It
-// will only change with a call to Configure or SetPeriod, otherwise it is
-// constant.
-//
-// The value returned here is hardware dependent. In general, it's best to treat
-// it as an opaque value that can be divided by some number and passed to Set
-// (see Set documentation for more information).
-func (tcc *TCC) Top() uint32 {
-	return tcc.timer().PER.Get() + 1
-}
-
-// Counter returns the current counter value of the timer in this TCC
-// peripheral. It may be useful for debugging.
-func (tcc *TCC) Counter() uint32 {
-	tcc.timer().CTRLBSET.Set(sam.TCC_CTRLBSET_CMD_READSYNC << sam.TCC_CTRLBSET_CMD_Pos)
-	for tcc.timer().SYNCBUSY.Get() != 0 {
-	}
-	return tcc.timer().COUNT.Get()
-}
-
-// Some constans to make pinTimerMapping below easier to read.
-const (
-	pinTCC0     = 1
-	pinTCC1     = 2
-	pinTCC2     = 3
-	pinTimerCh0 = 0 << 3
-	pinTimerCh2 = 1 << 3
-	pinTCC0Ch0  = pinTCC0 | pinTimerCh0
-	pinTCC0Ch2  = pinTCC0 | pinTimerCh2
-	pinTCC1Ch0  = pinTCC1 | pinTimerCh0
-	pinTCC1Ch2  = pinTCC1 | pinTimerCh2
-	pinTCC2Ch0  = pinTCC2 | pinTimerCh0
-)
-
-// Mapping from pin number to TCC peripheral and channel using a special
-// encoding. Note that only TCC0-TCC2 are included, not TC3 and up.
-// Every byte is split in two nibbles where the low nibble describes PinTCC and
-// the high nibble describes PinTCCAlt. Within a nibble, there is one bit that
-// indicates Ch0/Ch1 or Ch2/Ch3, and three other bits that contain the TCC
-// peripheral number plus one (to distinguish between TCC0Ch0 and 0).
-//
-// The encoding can be so compact because all pins are configured in pairs, so
-// if you know PA00 you can infer the configuration of PA01. And only channel 0
-// or 2 need to be included (taking up just one bit), because channel 0 and 2
-// are only ever used on odd pins and channel 1 and 3 on even pins, again using
-// the pin pair pattern to reduce the amount of information needed to be stored.
-//
-// Datasheet: https://cdn.sparkfun.com/datasheets/Dev/Arduino/Boards/Atmel-42181-SAM-D21_Datasheet.pdf
-var pinTimerMapping = [...]uint8{
-	// page 21
-	PA00 / 2: pinTCC2Ch0 | 0,
-	PA04 / 2: pinTCC0Ch0 | 0,
-	PA06 / 2: pinTCC1Ch0 | 0,
-	PA08 / 2: pinTCC0Ch0 | pinTCC1Ch2<<4,
-	PA10 / 2: pinTCC1Ch0 | pinTCC0Ch2<<4,
-	// page 22
-	PB10 / 2: 0 | pinTCC0Ch0<<4,
-	PB12 / 2: 0 | pinTCC0Ch2<<4,
-	PA12 / 2: pinTCC2Ch0 | pinTCC0Ch2<<4,
-	PA14 / 2: 0 | pinTCC0Ch0<<4,
-	PA16 / 2: pinTCC2Ch0 | pinTCC0Ch2<<4,
-	PA18 / 2: 0 | pinTCC0Ch2<<4,
-	PB16 / 2: 0 | pinTCC0Ch0<<4,
-	PA20 / 2: 0 | pinTCC0Ch2<<4,
-	PA22 / 2: 0 | pinTCC0Ch0<<4,
-	PA24 / 2: 0 | pinTCC1Ch2<<4,
-	// page 23
-	PA30 / 2: 0 | pinTCC1Ch0<<4,
-	PB30 / 2: pinTCC0Ch0 | pinTCC1Ch2<<4,
-}
-
-// findPinPadMapping returns the pin mode (PinTCC or PinTCCAlt) and the channel
-// number for a given timer and pin. A zero PinMode is returned if no mapping
-// could be found.
-func findPinTimerMapping(timer uint8, pin Pin) (PinMode, uint8) {
-	mapping := pinTimerMapping[pin/2]
-	// evenChannel below indicates the channel 0 or 2, for the even part of the
-	// pin pair. The next pin will also have the next channel (1 or 3).
-	if mapping&0x07 == timer+1 {
-		// PWM output is on peripheral function E.
-		evenChannel := ((mapping >> 3) & 1) * 2
-		return PinTCC, evenChannel + uint8(pin&1)
-	}
-	if (mapping&0x70)>>4 == timer+1 {
-		// PWM output is on peripheral function F.
-		evenChannel := ((mapping >> 7) & 1) * 2
-		return PinTCCAlt, evenChannel + uint8(pin&1)
-	}
-	return 0, 0
-}
-
-// Channel returns a PWM channel for the given pin. Note that one channel may be
-// shared between multiple pins, and so will have the same duty cycle. If this
-// is not desirable, look for a different TCC peripheral or consider using a
-// different pin.
-func (tcc *TCC) Channel(pin Pin) (uint8, error) {
-	var pinMode PinMode
-	var channel uint8
-	switch tcc.timer() {
-	case sam.TCC0:
-		pinMode, channel = findPinTimerMapping(0, pin)
-	case sam.TCC1:
-		pinMode, channel = findPinTimerMapping(1, pin)
-	case sam.TCC2:
-		pinMode, channel = findPinTimerMapping(2, pin)
+// Set turns on the duty cycle for a PWM pin using the provided value.
+func (pwm PWM) Set(value uint16) {
+	// figure out which TCCX timer for this pin
+	timer := pwm.getTimer()
+	if timer == nil {
+		// The Configure call above cannot have succeeded, so simply ignore this
+		// error.
+		return
 	}

-	if pinMode == 0 {
-		// No pin could be found.
-		return 0, ErrInvalidOutputPin
+	// disable output
+	timer.CTRLA.ClearBits(sam.TCC_CTRLA_ENABLE)
+
+	// Wait for synchronization
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_ENABLE) {
 	}

-	// Enable the port multiplexer for pin
-	pin.setPinCfg(sam.PORT_PINCFG0_PMUXEN)
-
-	if pin&1 > 0 {
-		// odd pin, so save the even pins
-		val := pin.getPMux() & sam.PORT_PMUX0_PMUXE_Msk
-		pin.setPMux(val | uint8(pinMode<<sam.PORT_PMUX0_PMUXO_Pos))
-	} else {
-		// even pin, so save the odd pins
-		val := pin.getPMux() & sam.PORT_PMUX0_PMUXO_Msk
-		pin.setPMux(val | uint8(pinMode<<sam.PORT_PMUX0_PMUXE_Pos))
-	}
-	return channel, nil
-}
-
-// SetInverting sets whether to invert the output of this channel.
-// Without inverting, a 25% duty cycle would mean the output is high for 25% of
-// the time and low for the rest. Inverting flips the output as if a NOT gate
-// was placed at the output, meaning that the output would be 25% low and 75%
-// high with a duty cycle of 25%.
-func (tcc *TCC) SetInverting(channel uint8, inverting bool) {
-	if inverting {
-		tcc.timer().WAVE.SetBits(1 << (sam.TCC_WAVE_POL0_Pos + channel))
-	} else {
-		tcc.timer().WAVE.ClearBits(1 << (sam.TCC_WAVE_POL0_Pos + channel))
-	}
-
-	// Wait for synchronization of the WAVE register.
-	for tcc.timer().SYNCBUSY.Get() != 0 {
-	}
-}
-
-// Set updates the channel value. This is used to control the channel duty
-// cycle, in other words the fraction of time the channel output is high (or low
-// when inverted). For example, to set it to a 25% duty cycle, use:
-//
-//     tcc.Set(channel, tcc.Top() / 4)
-//
-// tcc.Set(channel, 0) will set the output to low and tcc.Set(channel,
-// tcc.Top()) will set the output to high, assuming the output isn't inverted.
-func (tcc *TCC) Set(channel uint8, value uint32) {
 	// Set PWM signal to output duty cycle
-	switch channel {
-	case 0:
-		tcc.timer().CC0.Set(value)
-	case 1:
-		tcc.timer().CC1.Set(value)
-	case 2:
-		tcc.timer().CC2.Set(value)
-	case 3:
-		tcc.timer().CC3.Set(value)
-	default:
-		// invalid PWM channel, ignore.
+	pwm.setChannel(timer, uint32(value))
+
+	// Wait for synchronization on all channels
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_CC0 |
+		sam.TCC_SYNCBUSY_CC1 |
+		sam.TCC_SYNCBUSY_CC2 |
+		sam.TCC_SYNCBUSY_CC3) {
 	}

-	// Wait for synchronization on all channels (or anything in this peripheral,
-	// really).
-	for tcc.timer().SYNCBUSY.Get() != 0 {
+	// enable
+	timer.CTRLA.SetBits(sam.TCC_CTRLA_ENABLE)
+	// Wait for synchronization
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_ENABLE) {
+	}
+}
+
+// getPMux returns the value for the correct PMUX register for this pin.
+func (pwm PWM) getPMux() uint8 {
+	return pwm.Pin.getPMux()
+}
+
+// setPMux sets the value for the correct PMUX register for this pin.
+func (pwm PWM) setPMux(val uint8) {
+	pwm.Pin.setPMux(val)
+}
+
+// getPinCfg returns the value for the correct PINCFG register for this pin.
+func (pwm PWM) getPinCfg() uint8 {
+	return pwm.Pin.getPinCfg()
+}
+
+// setPinCfg sets the value for the correct PINCFG register for this pin.
+func (pwm PWM) setPinCfg(val uint8) {
+	pwm.Pin.setPinCfg(val)
+}
+
+// getTimer returns the timer to be used for PWM on this pin
+func (pwm PWM) getTimer() *sam.TCC_Type {
+	switch pwm.Pin {
+	case 6:
+		return sam.TCC1
+	case 7:
+		return sam.TCC1
+	case 8:
+		return sam.TCC1
+	case 9:
+		return sam.TCC1
+	case 14:
+		return sam.TCC0
+	case 15:
+		return sam.TCC0
+	case 16:
+		return sam.TCC0
+	case 17:
+		return sam.TCC0
+	case 18:
+		return sam.TCC0
+	case 19:
+		return sam.TCC0
+	case 20:
+		return sam.TCC0
+	case 21:
+		return sam.TCC0
+	default:
+		return nil // not supported on this pin
+	}
+}
+
+// setChannel sets the value for the correct channel for PWM on this pin
+func (pwm PWM) setChannel(timer *sam.TCC_Type, val uint32) {
+	switch pwm.Pin {
+	case 6:
+		timer.CC0.Set(val)
+	case 7:
+		timer.CC1.Set(val)
+	case 8:
+		timer.CC0.Set(val)
+	case 9:
+		timer.CC1.Set(val)
+	case 14:
+		timer.CC0.Set(val)
+	case 15:
+		timer.CC1.Set(val)
+	case 16:
+		timer.CC2.Set(val)
+	case 17:
+		timer.CC3.Set(val)
+	case 18:
+		timer.CC2.Set(val)
+	case 19:
+		timer.CC3.Set(val)
+	case 20:
+		timer.CC2.Set(val)
+	case 21:
+		timer.CC3.Set(val)
+	default:
+		return // not supported on this pin
 	}
 }

@@ -2242,7 +2126,7 @@ func handleStandardSetup(setup usbSetup) bool {
 func cdcSetup(setup usbSetup) bool {
 	if setup.bmRequestType == usb_REQUEST_DEVICETOHOST_CLASS_INTERFACE {
 		if setup.bRequest == usb_CDC_GET_LINE_CODING {
-			var b [cdcLineInfoSize]byte
+			b := make([]byte, 7)
 			b[0] = byte(usbLineInfo.dwDTERate)
 			b[1] = byte(usbLineInfo.dwDTERate >> 8)
 			b[2] = byte(usbLineInfo.dwDTERate >> 16)
@@ -2251,18 +2135,14 @@ func cdcSetup(setup usbSetup) bool {
 			b[5] = byte(usbLineInfo.bParityType)
 			b[6] = byte(usbLineInfo.bDataBits)

-			sendUSBPacket(0, b[:])
+			sendUSBPacket(0, b)
 			return true
 		}
 	}

 	if setup.bmRequestType == usb_REQUEST_HOSTTODEVICE_CLASS_INTERFACE {
 		if setup.bRequest == usb_CDC_SET_LINE_CODING {
-			b, err := receiveUSBControlPacket()
-			if err != nil {
-				return false
-			}
-
+			b := receiveUSBControlPacket()
 			usbLineInfo.dwDTERate = uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
 			usbLineInfo.bCharFormat = b[4]
 			usbLineInfo.bParityType = b[5]
@@ -2309,9 +2189,7 @@ func sendUSBPacket(ep uint32, data []byte) {
 	usbEndpointDescriptors[ep].DeviceDescBank[1].PCKSIZE.SetBits(uint32((len(data) & usb_DEVICE_PCKSIZE_BYTE_COUNT_Mask) << usb_DEVICE_PCKSIZE_BYTE_COUNT_Pos))
 }

-func receiveUSBControlPacket() ([cdcLineInfoSize]byte, error) {
-	var b [cdcLineInfoSize]byte
-
+func receiveUSBControlPacket() []byte {
 	// address
 	usbEndpointDescriptors[0].DeviceDescBank[0].ADDR.Set(uint32(uintptr(unsafe.Pointer(&udd_ep_out_cache_buffer[0]))))

@@ -2326,7 +2204,7 @@ func receiveUSBControlPacket() ([cdcLineInfoSize]byte, error) {
 	for (getEPSTATUS(0) & sam.USB_DEVICE_EPSTATUS_BK0RDY) == 0 {
 		timeout--
 		if timeout == 0 {
-			return b, errUSBCDCReadTimeout
+			return []byte{}
 		}
 	}

@@ -2335,7 +2213,7 @@ func receiveUSBControlPacket() ([cdcLineInfoSize]byte, error) {
 	for (getEPINTFLAG(0) & sam.USB_DEVICE_EPINTFLAG_TRCPT0) == 0 {
 		timeout--
 		if timeout == 0 {
-			return b, errUSBCDCReadTimeout
+			return []byte{}
 		}
 	}

@@ -2343,13 +2221,10 @@ func receiveUSBControlPacket() ([cdcLineInfoSize]byte, error) {
 	bytesread := uint32((usbEndpointDescriptors[0].DeviceDescBank[0].PCKSIZE.Get() >>
 		usb_DEVICE_PCKSIZE_BYTE_COUNT_Pos) & usb_DEVICE_PCKSIZE_BYTE_COUNT_Mask)

-	if bytesread != cdcLineInfoSize {
-		return b, errUSBCDCBytesRead
-	}
+	data := make([]byte, bytesread)
+	copy(data, udd_ep_out_cache_buffer[0][:])

-	copy(b[:7], udd_ep_out_cache_buffer[0][:7])
-
-	return b, nil
+	return data
 }

 func handleEndpoint(ep uint32) {
@@ -1,4 +1,4 @@
-// +build sam,atsamd51 sam,atsame5x
+// +build sam,atsamd51

 // Peripheral abstraction layer for the atsamd51.
 //
@@ -20,6 +20,8 @@ func CPUFrequency() uint32 {
 	return 120000000
 }

+type PinMode uint8
+
 const (
 	PinAnalog        PinMode = 1
 	PinSERCOM        PinMode = 2
@@ -38,13 +40,10 @@ const (
 	PinInput         PinMode = 15
 	PinInputPullup   PinMode = 16
 	PinOutput        PinMode = 17
-	PinTCCE          PinMode = PinTimer
-	PinTCCF          PinMode = PinTimerAlt
-	PinTCCG          PinMode = PinTCCPDEC
+	PinPWME          PinMode = PinTimer
+	PinPWMF          PinMode = PinTimerAlt
+	PinPWMG          PinMode = PinTCCPDEC
 	PinInputPulldown PinMode = 18
-	PinCAN           PinMode = 19
-	PinCAN0          PinMode = PinSDHC
-	PinCAN1          PinMode = PinCom
 )

 type PinChange uint8
@@ -628,18 +627,6 @@ func (p Pin) Configure(config PinConfig) {
 		}
 		// enable port config
 		p.setPinCfg(sam.PORT_GROUP_PINCFG_PMUXEN | sam.PORT_GROUP_PINCFG_DRVSTR)
-	case PinSDHC:
-		if p&1 > 0 {
-			// odd pin, so save the even pins
-			val := p.getPMux() & sam.PORT_GROUP_PMUX_PMUXE_Msk
-			p.setPMux(val | (uint8(PinSDHC) << sam.PORT_GROUP_PMUX_PMUXO_Pos))
-		} else {
-			// even pin, so save the odd pins
-			val := p.getPMux() & sam.PORT_GROUP_PMUX_PMUXO_Msk
-			p.setPMux(val | (uint8(PinSDHC) << sam.PORT_GROUP_PMUX_PMUXE_Pos))
-		}
-		// enable port config
-		p.setPinCfg(sam.PORT_GROUP_PINCFG_PMUXEN)
 	}
 }

@@ -813,18 +800,6 @@ func (a ADC) Configure(config ADCConfig) {
 	}

 	a.Pin.Configure(PinConfig{Mode: PinAnalog})
-
-	switch config.Bus {
-	case AdcBusAuto:
-		bus := a.getADCBus()
-		if bus == sam.ADC0 {
-			a.Bus = 0
-		} else {
-			a.Bus = 1
-		}
-	default:
-		a.Bus = config.Bus
-	}
 }

 // Get returns the current value of a ADC pin, in the range 0..0xffff.
@@ -873,27 +848,10 @@ func (a ADC) Get() uint16 {
 	for bus.SYNCBUSY.HasBits(sam.ADC_SYNCBUSY_ENABLE) {
 	}

-	// scales to 16-bit result
-	switch (bus.CTRLB.Get() & sam.ADC_CTRLB_RESSEL_Msk) >> sam.ADC_CTRLB_RESSEL_Pos {
-	case sam.ADC_CTRLB_RESSEL_8BIT:
-		val = val << 8
-	case sam.ADC_CTRLB_RESSEL_10BIT:
-		val = val << 6
-	case sam.ADC_CTRLB_RESSEL_16BIT:
-		val = val << 4
-	case sam.ADC_CTRLB_RESSEL_12BIT:
-		val = val << 4
-	}
-	return val
+	return uint16(val) << 4 // scales from 12 to 16-bit result
 }

 func (a ADC) getADCBus() *sam.ADC_Type {
-	if a.Bus == AdcBus0 {
-		return sam.ADC0
-	} else if a.Bus == AdcBus1 {
-		return sam.ADC1
-	}
-
 	if (a.Pin >= PB04 && a.Pin <= PB07) || (a.Pin >= PC00) {
 		return sam.ADC1
 	}
@@ -905,17 +863,9 @@ func (a ADC) getADCChannel() uint8 {
 	case PA02:
 		return 0
 	case PB08:
-		if a.Bus == AdcBus1 {
-			return 0
-		} else {
-			return 2
-		}
+		return 2
 	case PB09:
-		if a.Bus == AdcBus1 {
-			return 1
-		} else {
-			return 3
-		}
+		return 3
 	case PA04:
 		return 4
 	case PA05:
@@ -1620,350 +1570,256 @@ const (
 	QSPI_DATA3 = PA11
 )

-// TCC is one timer peripheral, which consists of a counter and multiple output
-// channels (that can be connected to actual pins). You can set the frequency
-// using SetPeriod, but only for all the channels in this timer peripheral at
-// once.
-type TCC sam.TCC_Type
+// PWM
+const period = 0xFFFF

-//go:inline
-func (tcc *TCC) timer() *sam.TCC_Type {
-	return (*sam.TCC_Type)(tcc)
-}
+// Configure configures a PWM pin for output.
+func (pwm PWM) Configure() error {
+	// Set pin as output
+	sam.PORT.GROUP[0].DIRSET.Set(1 << uint8(pwm.Pin))
+	// Set pin to low
+	sam.PORT.GROUP[0].OUTCLR.Set(1 << uint8(pwm.Pin))

-// Configure enables and configures this TCC.
-func (tcc *TCC) Configure(config PWMConfig) error {
-	// Enable the TCC clock to be able to use the TCC.
-	tcc.configureClock()
+	// Enable the port multiplexer for pin
+	pwm.setPinCfg(sam.PORT_GROUP_PINCFG_PMUXEN)

-	// Disable timer (if it was enabled). This is necessary because
-	// tcc.setPeriod may want to change the prescaler bits in CTRLA, which is
-	// only allowed when the TCC is disabled.
-	tcc.timer().CTRLA.ClearBits(sam.TCC_CTRLA_ENABLE)
+	// Connect timer/mux to pin.
+	pwmConfig := pwm.getMux()
+
+	if pwm.Pin&1 > 0 {
+		// odd pin, so save the even pins
+		val := pwm.getPMux() & sam.PORT_GROUP_PMUX_PMUXE_Msk
+		pwm.setPMux(val | uint8(pwmConfig<<sam.PORT_GROUP_PMUX_PMUXO_Pos))
+	} else {
+		// even pin, so save the odd pins
+		val := pwm.getPMux() & sam.PORT_GROUP_PMUX_PMUXO_Msk
+		pwm.setPMux(val | uint8(pwmConfig<<sam.PORT_GROUP_PMUX_PMUXE_Pos))
+	}
+
+	// figure out which TCCX timer for this pin
+	timer := pwm.getTimer()
+	if timer == nil {
+		return ErrInvalidOutputPin
+	}
+
+	// disable timer
+	timer.CTRLA.ClearBits(sam.TCC_CTRLA_ENABLE)
+	// Wait for synchronization
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_ENABLE) {
+	}
+
+	// Set prescaler to 1/256
+	// TCCx->CTRLA.reg = TCC_CTRLA_PRESCALER_DIV256 | TCC_CTRLA_PRESCSYNC_GCLK;
+	timer.CTRLA.SetBits(sam.TCC_CTRLA_PRESCALER_DIV256 | sam.TCC_CTRLA_PRESCSYNC_GCLK)

 	// Use "Normal PWM" (single-slope PWM)
-	tcc.timer().WAVE.Set(sam.TCC_WAVE_WAVEGEN_NPWM)
-
-	// Wait for synchronization of all changed registers.
-	for tcc.timer().SYNCBUSY.Get() != 0 {
+	timer.WAVE.SetBits(sam.TCC_WAVE_WAVEGEN_NPWM)
+	// Wait for synchronization
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_WAVE) {
 	}

-	// Set the period and prescaler.
-	err := tcc.setPeriod(config.Period, true)
-
-	// Enable the timer.
-	tcc.timer().CTRLA.SetBits(sam.TCC_CTRLA_ENABLE)
-
-	// Wait for synchronization of all changed registers.
-	for tcc.timer().SYNCBUSY.Get() != 0 {
+	// while (TCCx->SYNCBUSY.bit.CC0 || TCCx->SYNCBUSY.bit.CC1);
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_CC0) ||
+		timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_CC1) {
 	}

-	// Return any error that might have occured in the tcc.setPeriod call.
-	return err
-}
+	// Set the initial value
+	// TCCx->CC[tcChannel].reg = (uint32_t) value;
+	pwm.setChannel(timer, 0)

-// SetPeriod updates the period of this TCC peripheral.
-// To set a particular frequency, use the following formula:
-//
-//     period = 1e9 / frequency
-//
-// If you use a period of 0, a period that works well for LEDs will be picked.
-//
-// SetPeriod will not change the prescaler, but also won't change the current
-// value in any of the channels. This means that you may need to update the
-// value for the particular channel.
-//
-// Note that you cannot pick any arbitrary period after the TCC peripheral has
-// been configured. If you want to switch between frequencies, pick the lowest
-// frequency (longest period) once when calling Configure and adjust the
-// frequency here as needed.
-func (tcc *TCC) SetPeriod(period uint64) error {
-	return tcc.setPeriod(period, false)
-}
-
-// setPeriod sets the period of this TCC, possibly updating the prescaler as
-// well. The prescaler can only modified when the TCC is disabled, that is, in
-// the Configure function.
-func (tcc *TCC) setPeriod(period uint64, updatePrescaler bool) error {
-	var top uint64
-	if period == 0 {
-		// Make sure the TOP value is at 0xffff (enough for a 16-bit timer).
-		top = 0xffff
-	} else {
-		// The formula below calculates the following formula, optimized:
-		//     period * (120e6 / 1e9)
-		// This assumes that the chip is running from generic clock generator 0
-		// at 120MHz.
-		top = period * 3 / 25
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_CC0) ||
+		timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_CC1) {
 	}

-	maxTop := uint64(0xffff)
-	if tcc.timer() == sam.TCC0 || tcc.timer() == sam.TCC1 {
-		// Only TCC0 and TCC1 are 24-bit timers, the rest are 16-bit.
-		maxTop = 0xffffff
+	// Set the period (the number to count to (TOP) before resetting timer)
+	//TCC0->PER.reg = period;
+	timer.PER.Set(period)
+	// Wait for synchronization
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_PER) {
 	}

-	if updatePrescaler {
-		// This function was called during Configure(), with the timer disabled.
-		// Note that updating the prescaler can only happen while the peripheral
-		// is disabled.
-		var prescaler uint32
-		switch {
-		case top <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV1
-		case top/2 <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV2
-			top = top / 2
-		case top/4 <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV4
-			top = top / 4
-		case top/8 <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV8
-			top = top / 8
-		case top/16 <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV16
-			top = top / 16
-		case top/64 <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV64
-			top = top / 64
-		case top/256 <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV256
-			top = top / 256
-		case top/1024 <= maxTop:
-			prescaler = sam.TCC_CTRLA_PRESCALER_DIV1024
-			top = top / 1024
-		default:
-			return ErrPWMPeriodTooLong
-		}
-		tcc.timer().CTRLA.Set((tcc.timer().CTRLA.Get() &^ sam.TCC_CTRLA_PRESCALER_Msk) | (prescaler << sam.TCC_CTRLA_PRESCALER_Pos))
-	} else {
-		// Do not update the prescaler, but use the already-configured
-		// prescaler. This is the normal SetPeriod case, where the prescaler
-		// must not be changed.
-		prescaler := (tcc.timer().CTRLA.Get() & sam.TCC_CTRLA_PRESCALER_Msk) >> sam.TCC_CTRLA_PRESCALER_Pos
-		switch prescaler {
-		case sam.TCC_CTRLA_PRESCALER_DIV1:
-			top /= 1 // no-op
-		case sam.TCC_CTRLA_PRESCALER_DIV2:
-			top /= 2
-		case sam.TCC_CTRLA_PRESCALER_DIV4:
-			top /= 4
-		case sam.TCC_CTRLA_PRESCALER_DIV8:
-			top /= 8
-		case sam.TCC_CTRLA_PRESCALER_DIV16:
-			top /= 16
-		case sam.TCC_CTRLA_PRESCALER_DIV64:
-			top /= 64
-		case sam.TCC_CTRLA_PRESCALER_DIV256:
-			top /= 256
-		case sam.TCC_CTRLA_PRESCALER_DIV1024:
-			top /= 1024
-		default:
-			// unreachable
-		}
-		if top > maxTop {
-			return ErrPWMPeriodTooLong
-		}
-	}
-
-	// Set the period (the counter top).
-	tcc.timer().PER.Set(uint32(top) - 1)
-
-	// Wait for synchronization of CTRLA.PRESCALER and PER registers.
-	for tcc.timer().SYNCBUSY.Get() != 0 {
+	// enable timer
+	timer.CTRLA.SetBits(sam.TCC_CTRLA_ENABLE)
+	// Wait for synchronization
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_ENABLE) {
 	}

 	return nil
 }

-// Top returns the current counter top, for use in duty cycle calculation. It
-// will only change with a call to Configure or SetPeriod, otherwise it is
-// constant.
-//
-// The value returned here is hardware dependent. In general, it's best to treat
-// it as an opaque value that can be divided by some number and passed to
-// tcc.Set (see tcc.Set for more information).
-func (tcc *TCC) Top() uint32 {
-	return tcc.timer().PER.Get() + 1
-}
-
-// Counter returns the current counter value of the timer in this TCC
-// peripheral. It may be useful for debugging.
-func (tcc *TCC) Counter() uint32 {
-	tcc.timer().CTRLBSET.Set(sam.TCC_CTRLBSET_CMD_READSYNC << sam.TCC_CTRLBSET_CMD_Pos)
-	for tcc.timer().SYNCBUSY.Get() != 0 {
-	}
-	return tcc.timer().COUNT.Get()
-}
-
-// Constants that encode a TCC number and WO number together in a single byte.
-const (
-	pinTCC0   = 1 << 4 // keep the value 0 usable as "no value"
-	pinTCC1   = 2 << 4
-	pinTCC2   = 3 << 4
-	pinTCC3   = 4 << 4
-	pinTCC4   = 5 << 4
-	pinTCC0_0 = pinTCC0 | 0
-	pinTCC0_1 = pinTCC0 | 1
-	pinTCC0_2 = pinTCC0 | 2
-	pinTCC0_3 = pinTCC0 | 3
-	pinTCC0_4 = pinTCC0 | 4
-	pinTCC0_5 = pinTCC0 | 5
-	pinTCC0_6 = pinTCC0 | 6
-	pinTCC1_0 = pinTCC1 | 0
-	pinTCC1_2 = pinTCC1 | 2
-	pinTCC1_4 = pinTCC1 | 4
-	pinTCC1_6 = pinTCC1 | 6
-	pinTCC2_0 = pinTCC2 | 0
-	pinTCC2_2 = pinTCC2 | 2
-	pinTCC3_0 = pinTCC3 | 0
-	pinTCC4_0 = pinTCC4 | 0
-)
-
-// This is a copy of columns F and G (the TCC columns) of table 6-1 in the
-// datasheet:
-// http://ww1.microchip.com/downloads/en/DeviceDoc/60001507E.pdf
-// For example, "TCC0/WO[2]" is converted to pinTCC0_2.
-// Only the even pin numbers are stored here. The odd pin numbers are left out,
-// because their PWM output can be determined from the even number: just add one
-// to the wave output (WO) number.
-var pinTimerMapping = [...]struct{ F, G uint8 }{
-	// page 33
-	PC04 / 2: {pinTCC0_0, 0},
-	PA08 / 2: {pinTCC0_0, pinTCC1_4},
-	PA10 / 2: {pinTCC0_2, pinTCC1_6},
-	PB10 / 2: {pinTCC0_4, pinTCC1_0},
-	PB12 / 2: {pinTCC3_0, pinTCC0_0},
-	PB14 / 2: {pinTCC4_0, pinTCC0_2},
-	PD08 / 2: {pinTCC0_1, 0},
-	PD10 / 2: {pinTCC0_3, 0},
-	PD12 / 2: {pinTCC0_5, 0},
-	PC10 / 2: {pinTCC0_0, pinTCC1_4},
-	// page 34
-	PC12 / 2: {pinTCC0_2, pinTCC1_6},
-	PC14 / 2: {pinTCC0_4, pinTCC1_0},
-	PA12 / 2: {pinTCC0_6, pinTCC1_2},
-	PA14 / 2: {pinTCC2_0, pinTCC1_2},
-	PA16 / 2: {pinTCC1_0, pinTCC0_4},
-	PA18 / 2: {pinTCC1_2, pinTCC0_6},
-	PC16 / 2: {pinTCC0_0, 0},
-	PC18 / 2: {pinTCC0_2, 0},
-	PC20 / 2: {pinTCC0_4, 0},
-	PC22 / 2: {pinTCC0_6, 0},
-	PD20 / 2: {pinTCC1_0, 0},
-	PB16 / 2: {pinTCC3_0, pinTCC0_4},
-	PB18 / 2: {pinTCC1_0, 0},
-	// page 35
-	PB20 / 2: {pinTCC1_2, 0},
-	PA20 / 2: {pinTCC1_4, pinTCC0_0},
-	PA22 / 2: {pinTCC1_6, pinTCC0_2},
-	PA24 / 2: {pinTCC2_2, 0},
-	PB26 / 2: {pinTCC1_2, 0},
-	PB28 / 2: {pinTCC1_4, 0},
-	PA30 / 2: {pinTCC2_0, 0},
-	// page 36
-	PB30 / 2: {pinTCC4_0, pinTCC0_6},
-	PB02 / 2: {pinTCC2_2, 0},
-}
-
-// findPinPadMapping returns the pin mode (PinTCCF or PinTCCG) and the channel
-// number for a given timer and pin. A zero PinMode is returned if no mapping
-// could be found.
-func findPinTimerMapping(timer uint8, pin Pin) (PinMode, uint8) {
-	if int(pin/2) >= len(pinTimerMapping) {
-		return 0, 0 // invalid pin number
+// Set turns on the duty cycle for a PWM pin using the provided value.
+func (pwm PWM) Set(value uint16) {
+	// figure out which TCCX timer for this pin
+	timer := pwm.getTimer()
+	if timer == nil {
+		// The Configure call above cannot have succeeded, so simply ignore this
+		// error.
+		return
 	}

-	mapping := pinTimerMapping[pin/2]
-
-	// Check for column F in the datasheet.
-	if mapping.F>>4-1 == timer {
-		return PinTCCF, mapping.F&0x0f + uint8(pin)&1
+	// Wait for synchronization
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_CTRLB) {
+	}
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_CC0) ||
+		timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_CC1) {
 	}

-	// Check for column G in the datasheet.
-	if mapping.G>>4-1 == timer {
-		return PinTCCG, mapping.G&0x0f + uint8(pin)&1
+	// TCCx->CCBUF[tcChannel].reg = (uint32_t) value;
+	pwm.setChannelBuffer(timer, uint32(value))
+
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_CC0) ||
+		timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_CC1) {
 	}

-	// Nothing found.
-	return 0, 0
-}
-
-// Channel returns a PWM channel for the given pin. Note that one channel may be
-// shared between multiple pins, and so will have the same duty cycle. If this
-// is not desirable, look for a different TCC or consider using a different pin.
-func (tcc *TCC) Channel(pin Pin) (uint8, error) {
-	pinMode, woOutput := findPinTimerMapping(tcc.timerNum(), pin)
-
-	if pinMode == 0 {
-		// No pin could be found.
-		return 0, ErrInvalidOutputPin
-	}
-
-	// Convert from waveform output to channel, assuming WEXCTRL.OTMX equals 0.
-	// See table 49-4 "Output Matrix Channel Pin Routing Configuration" on page
-	// 1829 of the datasheet.
-	// The number of channels varies by TCC instance, hence the need to switch
-	// over them. For TCC2-4 the number of channels is equal to the number of
-	// waveform outputs, so the WO number maps directly to the channel number.
-	// For TCC0 and TCC1 this is not the case so they will need some special
-	// handling.
-	channel := woOutput
-	switch tcc.timer() {
-	case sam.TCC0:
-		channel = woOutput % 6
-	case sam.TCC1:
-		channel = woOutput % 4
-	}
-
-	// Enable the port multiplexer for pin
-	pin.setPinCfg(sam.PORT_GROUP_PINCFG_PMUXEN)
-
-	// Connect timer/mux to pin.
-	if pin&1 > 0 {
-		// odd pin, so save the even pins
-		val := pin.getPMux() & sam.PORT_GROUP_PMUX_PMUXE_Msk
-		pin.setPMux(val | uint8(pinMode<<sam.PORT_GROUP_PMUX_PMUXO_Pos))
-	} else {
-		// even pin, so save the odd pins
-		val := pin.getPMux() & sam.PORT_GROUP_PMUX_PMUXO_Msk
-		pin.setPMux(val | uint8(pinMode<<sam.PORT_GROUP_PMUX_PMUXE_Pos))
-	}
-
-	return channel, nil
-}
-
-// SetInverting sets whether to invert the output of this channel.
-// Without inverting, a 25% duty cycle would mean the output is high for 25% of
-// the time and low for the rest. Inverting flips the output as if a NOT gate
-// was placed at the output, meaning that the output would be 25% low and 75%
-// high with a duty cycle of 25%.
-func (tcc *TCC) SetInverting(channel uint8, inverting bool) {
-	if inverting {
-		tcc.timer().WAVE.SetBits(1 << (sam.TCC_WAVE_POL0_Pos + channel))
-	} else {
-		tcc.timer().WAVE.ClearBits(1 << (sam.TCC_WAVE_POL0_Pos + channel))
-	}
-
-	// Wait for synchronization of the WAVE register.
-	for tcc.timer().SYNCBUSY.Get() != 0 {
+	// TCCx->CTRLBCLR.bit.LUPD = 1;
+	timer.CTRLBCLR.SetBits(sam.TCC_CTRLBCLR_LUPD)
+	for timer.SYNCBUSY.HasBits(sam.TCC_SYNCBUSY_CTRLB) {
 	}
 }

-// Set updates the channel value. This is used to control the channel duty
-// cycle, in other words the fraction of time the channel output is high (or low
-// when inverted). For example, to set it to a 25% duty cycle, use:
-//
-//     tcc.Set(channel, tcc.Top() / 4)
-//
-// tcc.Set(channel, 0) will set the output to low and tcc.Set(channel,
-// tcc.Top()) will set the output to high, assuming the output isn't inverted.
-func (tcc *TCC) Set(channel uint8, value uint32) {
-	// Update CCBUF, which provides double buffering. The update is applied on
-	// the next cycle.
-	tcc.timer().CCBUF[channel].Set(value)
-	for tcc.timer().SYNCBUSY.Get() != 0 {
+// getPMux returns the value for the correct PMUX register for this pin.
+func (pwm PWM) getPMux() uint8 {
+	return pwm.Pin.getPMux()
+}
+
+// setPMux sets the value for the correct PMUX register for this pin.
+func (pwm PWM) setPMux(val uint8) {
+	pwm.Pin.setPMux(val)
+}
+
+// getPinCfg returns the value for the correct PINCFG register for this pin.
+func (pwm PWM) getPinCfg() uint8 {
+	return pwm.Pin.getPinCfg()
+}
+
+// setPinCfg sets the value for the correct PINCFG register for this pin.
+func (pwm PWM) setPinCfg(val uint8) {
+	pwm.Pin.setPinCfg(val)
+}
+
+// setChannel sets the value for the correct channel for PWM on this pin.
+func (pwm PWM) setChannel(timer *sam.TCC_Type, val uint32) {
+	switch pwm.Pin {
+	case PA14:
+		timer.CC[0].Set(val)
+	case PA15:
+		timer.CC[1].Set(val)
+	case PA16:
+		timer.CC[0].Set(val)
+	case PA17:
+		timer.CC[1].Set(val)
+	case PA18:
+		timer.CC[2].Set(val)
+	case PA19:
+		timer.CC[3].Set(val)
+	case PA20:
+		timer.CC[0].Set(val)
+	case PA21:
+		timer.CC[1].Set(val)
+	case PA22:
+		timer.CC[2].Set(val)
+	case PA23:
+		timer.CC[3].Set(val)
+	case PB12:
+		timer.CC[0].Set(val)
+	case PB13:
+		timer.CC[1].Set(val)
+	case PB14:
+		timer.CC[0].Set(val)
+	case PB15:
+		timer.CC[1].Set(val)
+	case PB16:
+		timer.CC[4].Set(val)
+	case PB17:
+		timer.CC[5].Set(val)
+	case PB31:
+		timer.CC[1].Set(val)
+	default:
+		return // not supported on this pin
+	}
+}
+
+// setChannelBuffer sets the value for the correct channel buffer for PWM on this pin
+func (pwm PWM) setChannelBuffer(timer *sam.TCC_Type, val uint32) {
+	switch pwm.Pin {
+	case PA14:
+		timer.CCBUF[0].Set(val)
+	case PA15:
+		timer.CCBUF[1].Set(val)
+	case PA16:
+		timer.CCBUF[0].Set(val)
+	case PA17:
+		timer.CCBUF[1].Set(val)
+	case PA18:
+		timer.CCBUF[2].Set(val)
+	case PA19:
+		timer.CCBUF[3].Set(val)
+	case PA20:
+		timer.CCBUF[0].Set(val)
+	case PA21:
+		timer.CCBUF[1].Set(val)
+	case PA22:
+		timer.CCBUF[2].Set(val)
+	case PA23:
+		timer.CCBUF[3].Set(val)
+	case PB12:
+		timer.CCBUF[0].Set(val)
+	case PB13:
+		timer.CCBUF[1].Set(val)
+	case PB14:
+		timer.CCBUF[0].Set(val)
+	case PB15:
+		timer.CCBUF[1].Set(val)
+	case PB16:
+		timer.CCBUF[4].Set(val)
+	case PB17:
+		timer.CCBUF[5].Set(val)
+	case PB31:
+		timer.CCBUF[1].Set(val)
+	default:
+		return // not supported on this pin
+	}
+}
+
+// getMux returns the pin mode mux to be used for PWM on this pin.
+func (pwm PWM) getMux() PinMode {
+	switch pwm.Pin {
+	case PA14:
+		return PinPWMF
+	case PA15:
+		return PinPWMF
+	case PA16:
+		return PinPWMF
+	case PA17:
+		return PinPWMF
+	case PA18:
+		return PinPWMF
+	case PA19:
+		return PinPWMF
+	case PA20:
+		return PinPWMG
+	case PA21:
+		return PinPWMG
+	case PA22:
+		return PinPWMG
+	case PA23:
+		return PinPWMG
+	case PB12:
+		return PinPWMF
+	case PB13:
+		return PinPWMF
+	case PB14:
+		return PinPWMF
+	case PB15:
+		return PinPWMF
+	case PB16:
+		return PinPWMG
+	case PB17:
+		return PinPWMG
+	case PB31:
+		return PinPWMF
+	default:
+		return 0 // not supported on this pin
 	}
 }

@@ -2476,7 +2332,7 @@ func handleStandardSetup(setup usbSetup) bool {
 func cdcSetup(setup usbSetup) bool {
 	if setup.bmRequestType == usb_REQUEST_DEVICETOHOST_CLASS_INTERFACE {
 		if setup.bRequest == usb_CDC_GET_LINE_CODING {
-			var b [cdcLineInfoSize]byte
+			b := make([]byte, 7)
 			b[0] = byte(usbLineInfo.dwDTERate)
 			b[1] = byte(usbLineInfo.dwDTERate >> 8)
 			b[2] = byte(usbLineInfo.dwDTERate >> 16)
@@ -2485,18 +2341,14 @@ func cdcSetup(setup usbSetup) bool {
 			b[5] = byte(usbLineInfo.bParityType)
 			b[6] = byte(usbLineInfo.bDataBits)

-			sendUSBPacket(0, b[:])
+			sendUSBPacket(0, b)
 			return true
 		}
 	}

 	if setup.bmRequestType == usb_REQUEST_HOSTTODEVICE_CLASS_INTERFACE {
 		if setup.bRequest == usb_CDC_SET_LINE_CODING {
-			b, err := receiveUSBControlPacket()
-			if err != nil {
-				return false
-			}
-
+			b := receiveUSBControlPacket()
 			usbLineInfo.dwDTERate = uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
 			usbLineInfo.bCharFormat = b[4]
 			usbLineInfo.bParityType = b[5]
@@ -2543,9 +2395,7 @@ func sendUSBPacket(ep uint32, data []byte) {
 	usbEndpointDescriptors[ep].DeviceDescBank[1].PCKSIZE.SetBits(uint32((len(data) & usb_DEVICE_PCKSIZE_BYTE_COUNT_Mask) << usb_DEVICE_PCKSIZE_BYTE_COUNT_Pos))
 }

-func receiveUSBControlPacket() ([cdcLineInfoSize]byte, error) {
-	var b [cdcLineInfoSize]byte
-
+func receiveUSBControlPacket() []byte {
 	// address
 	usbEndpointDescriptors[0].DeviceDescBank[0].ADDR.Set(uint32(uintptr(unsafe.Pointer(&udd_ep_out_cache_buffer[0]))))

@@ -2560,7 +2410,7 @@ func receiveUSBControlPacket() ([cdcLineInfoSize]byte, error) {
 	for (getEPSTATUS(0) & sam.USB_DEVICE_ENDPOINT_EPSTATUS_BK0RDY) == 0 {
 		timeout--
 		if timeout == 0 {
-			return b, errUSBCDCReadTimeout
+			return []byte{}
 		}
 	}

@@ -2569,7 +2419,7 @@ func receiveUSBControlPacket() ([cdcLineInfoSize]byte, error) {
 	for (getEPINTFLAG(0) & sam.USB_DEVICE_ENDPOINT_EPINTFLAG_TRCPT1) == 0 {
 		timeout--
 		if timeout == 0 {
-			return b, errUSBCDCReadTimeout
+			return []byte{}
 		}
 	}

@@ -2577,13 +2427,10 @@ func receiveUSBControlPacket() ([cdcLineInfoSize]byte, error) {
 	bytesread := uint32((usbEndpointDescriptors[0].DeviceDescBank[0].PCKSIZE.Get() >>
 		usb_DEVICE_PCKSIZE_BYTE_COUNT_Pos) & usb_DEVICE_PCKSIZE_BYTE_COUNT_Mask)

-	if bytesread != cdcLineInfoSize {
-		return b, errUSBCDCBytesRead
-	}
+	data := make([]byte, bytesread)
+	copy(data, udd_ep_out_cache_buffer[0][:])

-	copy(b[:7], udd_ep_out_cache_buffer[0][:7])
-
-	return b, nil
+	return data
 }

 func handleEndpoint(ep uint32) {
@@ -11,37 +11,43 @@ import "device/sam"

 const HSRAM_SIZE = 0x00030000

-// This chip has three TCC peripherals, which have PWM as one feature.
-var (
-	TCC0 = (*TCC)(sam.TCC0)
-	TCC1 = (*TCC)(sam.TCC1)
-	TCC2 = (*TCC)(sam.TCC2)
-)
+// InitPWM initializes the PWM interface.
+func InitPWM() {
+	// turn on timer clocks used for PWM
+	sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_ | sam.MCLK_APBBMASK_TCC1_)
+	sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_)

-func (tcc *TCC) configureClock() {
-	// Turn on timer clocks used for TCC and use generic clock generator 0.
-	switch tcc.timer() {
-	case sam.TCC0:
-		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC1:
-		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC1_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC1].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC2:
-		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	}
+	//use clock generator 0
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
 }

-func (tcc *TCC) timerNum() uint8 {
-	switch tcc.timer() {
-	case sam.TCC0:
-		return 0
-	case sam.TCC1:
-		return 1
-	case sam.TCC2:
-		return 2
+// getTimer returns the timer to be used for PWM on this pin
+func (pwm PWM) getTimer() *sam.TCC_Type {
+	switch pwm.Pin {
+	case PA14:
+		return sam.TCC2
+	case PA15:
+		return sam.TCC2
+	case PA16:
+		return sam.TCC1
+	case PA17:
+		return sam.TCC1
+	case PA18:
+		return sam.TCC1
+	case PA19:
+		return sam.TCC1
+	case PA20:
+		return sam.TCC0
+	case PA21:
+		return sam.TCC0
+	case PA22:
+		return sam.TCC0
+	case PA23:
+		return sam.TCC0
 	default:
-		return 0x0f // should not happen
+		return nil // not supported on this pin
 	}
 }
@@ -11,49 +11,60 @@ import "device/sam"

 const HSRAM_SIZE = 0x00030000

-// This chip has five TCC peripherals, which have PWM as one feature.
-var (
-	TCC0 = (*TCC)(sam.TCC0)
-	TCC1 = (*TCC)(sam.TCC1)
-	TCC2 = (*TCC)(sam.TCC2)
-	TCC3 = (*TCC)(sam.TCC3)
-	TCC4 = (*TCC)(sam.TCC4)
-)
+// InitPWM initializes the PWM interface.
+func InitPWM() {
+	// turn on timer clocks used for PWM
+	sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_ | sam.MCLK_APBBMASK_TCC1_)
+	sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_ | sam.MCLK_APBCMASK_TCC3_)
+	sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_TCC4_)

-func (tcc *TCC) configureClock() {
-	// Turn on timer clocks used for the TCC and use generic clock generator 0.
-	switch tcc.timer() {
-	case sam.TCC0:
-		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC1:
-		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC1_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC1].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC2:
-		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC3:
-		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC3_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC3].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC4:
-		sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_TCC4_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC4].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	}
+	//use clock generator 0
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC4].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
 }

-func (tcc *TCC) timerNum() uint8 {
-	switch tcc.timer() {
-	case sam.TCC0:
-		return 0
-	case sam.TCC1:
-		return 1
-	case sam.TCC2:
-		return 2
-	case sam.TCC3:
-		return 3
-	case sam.TCC4:
-		return 4
+// getTimer returns the timer to be used for PWM on this pin
+func (pwm PWM) getTimer() *sam.TCC_Type {
+	switch pwm.Pin {
+	case PA14:
+		return sam.TCC2
+	case PA15:
+		return sam.TCC2
+	case PA16:
+		return sam.TCC1
+	case PA17:
+		return sam.TCC1
+	case PA18:
+		return sam.TCC1
+	case PA19:
+		return sam.TCC1
+	case PA20:
+		return sam.TCC0
+	case PA21:
+		return sam.TCC0
+	case PA22:
+		return sam.TCC0
+	case PA23:
+		return sam.TCC0
+	case PB12:
+		return sam.TCC3
+	case PB13:
+		return sam.TCC3
+	case PB14:
+		return sam.TCC4
+	case PB15:
+		return sam.TCC4
+	case PB16:
+		return sam.TCC0
+	case PB17:
+		return sam.TCC0
+	case PB31:
+		return sam.TCC4
 	default:
-		return 0x0f // should not happen
+		return nil // not supported on this pin
 	}
 }
@@ -11,49 +11,60 @@ import "device/sam"

 const HSRAM_SIZE = 0x00040000

-// This chip has five TCC peripherals, which have PWM as one feature.
-var (
-	TCC0 = (*TCC)(sam.TCC0)
-	TCC1 = (*TCC)(sam.TCC1)
-	TCC2 = (*TCC)(sam.TCC2)
-	TCC3 = (*TCC)(sam.TCC3)
-	TCC4 = (*TCC)(sam.TCC4)
-)
+// InitPWM initializes the PWM interface.
+func InitPWM() {
+	// turn on timer clocks used for PWM
+	sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_ | sam.MCLK_APBBMASK_TCC1_)
+	sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_ | sam.MCLK_APBCMASK_TCC3_)
+	sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_TCC4_)

-func (tcc *TCC) configureClock() {
-	// Turn on timer clocks used for TCC and use generic clock generator 0.
-	switch tcc.timer() {
-	case sam.TCC0:
-		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC1:
-		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC1_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC1].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC2:
-		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC3:
-		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC3_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC3].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC4:
-		sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_TCC4_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC4].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	}
+	//use clock generator 0
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC4].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
 }

-func (tcc *TCC) timerNum() uint8 {
-	switch tcc.timer() {
-	case sam.TCC0:
-		return 0
-	case sam.TCC1:
-		return 1
-	case sam.TCC2:
-		return 2
-	case sam.TCC3:
-		return 3
-	case sam.TCC4:
-		return 4
+// getTimer returns the timer to be used for PWM on this pin
+func (pwm PWM) getTimer() *sam.TCC_Type {
+	switch pwm.Pin {
+	case PA14:
+		return sam.TCC2
+	case PA15:
+		return sam.TCC2
+	case PA16:
+		return sam.TCC1
+	case PA17:
+		return sam.TCC1
+	case PA18:
+		return sam.TCC1
+	case PA19:
+		return sam.TCC1
+	case PA20:
+		return sam.TCC0
+	case PA21:
+		return sam.TCC0
+	case PA22:
+		return sam.TCC0
+	case PA23:
+		return sam.TCC0
+	case PB12:
+		return sam.TCC3
+	case PB13:
+		return sam.TCC3
+	case PB14:
+		return sam.TCC4
+	case PB15:
+		return sam.TCC4
+	case PB16:
+		return sam.TCC0
+	case PB17:
+		return sam.TCC0
+	case PB31:
+		return sam.TCC4
 	default:
-		return 0x0f // should not happen
+		return nil // not supported on this pin
 	}
 }
@@ -11,49 +11,60 @@ import "device/sam"

 const HSRAM_SIZE = 0x00030000

-// This chip has five TCC peripherals, which have PWM as one feature.
-var (
-	TCC0 = (*TCC)(sam.TCC0)
-	TCC1 = (*TCC)(sam.TCC1)
-	TCC2 = (*TCC)(sam.TCC2)
-	TCC3 = (*TCC)(sam.TCC3)
-	TCC4 = (*TCC)(sam.TCC4)
-)
+// InitPWM initializes the PWM interface.
+func InitPWM() {
+	// turn on timer clocks used for PWM
+	sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_ | sam.MCLK_APBBMASK_TCC1_)
+	sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_ | sam.MCLK_APBCMASK_TCC3_)
+	sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_TCC4_)

-func (tcc *TCC) configureClock() {
-	// Turn on timer clocks used for TCC and use generic clock generator 0.
-	switch tcc.timer() {
-	case sam.TCC0:
-		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC1:
-		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC1_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC1].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC2:
-		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC3:
-		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC3_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC3].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC4:
-		sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_TCC4_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC4].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	}
+	//use clock generator 0
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC4].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
 }

-func (tcc *TCC) timerNum() uint8 {
-	switch tcc.timer() {
-	case sam.TCC0:
-		return 0
-	case sam.TCC1:
-		return 1
-	case sam.TCC2:
-		return 2
-	case sam.TCC3:
-		return 3
-	case sam.TCC4:
-		return 4
+// getTimer returns the timer to be used for PWM on this pin
+func (pwm PWM) getTimer() *sam.TCC_Type {
+	switch pwm.Pin {
+	case PA14:
+		return sam.TCC2
+	case PA15:
+		return sam.TCC2
+	case PA16:
+		return sam.TCC1
+	case PA17:
+		return sam.TCC1
+	case PA18:
+		return sam.TCC1
+	case PA19:
+		return sam.TCC1
+	case PA20:
+		return sam.TCC0
+	case PA21:
+		return sam.TCC0
+	case PA22:
+		return sam.TCC0
+	case PA23:
+		return sam.TCC0
+	case PB12:
+		return sam.TCC3
+	case PB13:
+		return sam.TCC3
+	case PB14:
+		return sam.TCC4
+	case PB15:
+		return sam.TCC4
+	case PB16:
+		return sam.TCC0
+	case PB17:
+		return sam.TCC0
+	case PB31:
+		return sam.TCC4
 	default:
-		return 0x0f // should not happen
+		return nil // not supported on this pin
 	}
 }
@@ -11,49 +11,60 @@ import "device/sam"

 const HSRAM_SIZE = 0x00040000

-// This chip has five TCC peripherals, which have PWM as one feature.
-var (
-	TCC0 = (*TCC)(sam.TCC0)
-	TCC1 = (*TCC)(sam.TCC1)
-	TCC2 = (*TCC)(sam.TCC2)
-	TCC3 = (*TCC)(sam.TCC3)
-	TCC4 = (*TCC)(sam.TCC4)
-)
+// InitPWM initializes the PWM interface.
+func InitPWM() {
+	// turn on timer clocks used for PWM
+	sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_ | sam.MCLK_APBBMASK_TCC1_)
+	sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_ | sam.MCLK_APBCMASK_TCC3_)
+	sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_TCC4_)

-func (tcc *TCC) configureClock() {
-	// Turn on timer clocks used for TCC and use generic clock generator 0.
-	switch tcc.timer() {
-	case sam.TCC0:
-		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC1:
-		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC1_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC1].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC2:
-		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC3:
-		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC3_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC3].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC4:
-		sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_TCC4_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC4].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	}
+	//use clock generator 0
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC4].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
 }

-func (tcc *TCC) timerNum() uint8 {
-	switch tcc.timer() {
-	case sam.TCC0:
-		return 0
-	case sam.TCC1:
-		return 1
-	case sam.TCC2:
-		return 2
-	case sam.TCC3:
-		return 3
-	case sam.TCC4:
-		return 4
+// getTimer returns the timer to be used for PWM on this pin
+func (pwm PWM) getTimer() *sam.TCC_Type {
+	switch pwm.Pin {
+	case PC18:
+		return sam.TCC0
+	case PC19:
+		return sam.TCC0
+	case PC20:
+		return sam.TCC0
+	case PC21:
+		return sam.TCC0
+	case PD20:
+		return sam.TCC1
+	case PD21:
+		return sam.TCC1
+	case PB18:
+		return sam.TCC1
+	case PB12:
+		return sam.TCC3
+	case PB13:
+		return sam.TCC3
+	case PA15:
+		return sam.TCC2
+	case PC17:
+		return sam.TCC0
+	case PC16:
+		return sam.TCC0
+	case PA14:
+		return sam.TCC2
+	case PB15:
+		return sam.TCC4
+	case PB14:
+		return sam.TCC4
+	case PB20:
+		return sam.TCC1
+	case PB21:
+		return sam.TCC1
 	default:
-		return 0x0f // should not happen
+		return nil // not supported on this pin
 	}
 }
@@ -1,59 +0,0 @@
-// +build sam,atsame51,atsame51j19
-
-// Peripheral abstraction layer for the atsame51.
-//
-// Datasheet:
-// http://ww1.microchip.com/downloads/en/DeviceDoc/SAM_D5xE5x_Family_Data_Sheet_DS60001507F.pdf
-//
-package machine
-
-import "device/sam"
-
-const HSRAM_SIZE = 0x00030000
-
-// This chip has five TCC peripherals, which have PWM as one feature.
-var (
-	TCC0 = (*TCC)(sam.TCC0)
-	TCC1 = (*TCC)(sam.TCC1)
-	TCC2 = (*TCC)(sam.TCC2)
-	TCC3 = (*TCC)(sam.TCC3)
-	TCC4 = (*TCC)(sam.TCC4)
-)
-
-func (tcc *TCC) configureClock() {
-	// Turn on timer clocks used for the TCC and use generic clock generator 0.
-	switch tcc.timer() {
-	case sam.TCC0:
-		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC1:
-		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC1_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC1].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC2:
-		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC3:
-		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC3_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC3].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC4:
-		sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_TCC4_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC4].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	}
-}
-
-func (tcc *TCC) timerNum() uint8 {
-	switch tcc.timer() {
-	case sam.TCC0:
-		return 0
-	case sam.TCC1:
-		return 1
-	case sam.TCC2:
-		return 2
-	case sam.TCC3:
-		return 3
-	case sam.TCC4:
-		return 4
-	default:
-		return 0x0f // should not happen
-	}
-}
@@ -1,59 +0,0 @@
-// +build sam,atsame5x,atsame54p20
-
-// Peripheral abstraction layer for the atsame54.
-//
-// Datasheet:
-// http://ww1.microchip.com/downloads/en/DeviceDoc/60001507C.pdf
-//
-package machine
-
-import "device/sam"
-
-const HSRAM_SIZE = 0x00040000
-
-// This chip has five TCC peripherals, which have PWM as one feature.
-var (
-	TCC0 = (*TCC)(sam.TCC0)
-	TCC1 = (*TCC)(sam.TCC1)
-	TCC2 = (*TCC)(sam.TCC2)
-	TCC3 = (*TCC)(sam.TCC3)
-	TCC4 = (*TCC)(sam.TCC4)
-)
-
-func (tcc *TCC) configureClock() {
-	// Turn on timer clocks used for TCC and use generic clock generator 0.
-	switch tcc.timer() {
-	case sam.TCC0:
-		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC1:
-		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC1_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC1].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC2:
-		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC3:
-		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC3_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC3].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	case sam.TCC4:
-		sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_TCC4_)
-		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC4].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
-	}
-}
-
-func (tcc *TCC) timerNum() uint8 {
-	switch tcc.timer() {
-	case sam.TCC0:
-		return 0
-	case sam.TCC1:
-		return 1
-	case sam.TCC2:
-		return 2
-	case sam.TCC3:
-		return 3
-	case sam.TCC4:
-		return 4
-	default:
-		return 0x0f // should not happen
-	}
-}
@@ -8,6 +8,8 @@ import (
 	"unsafe"
 )

+type PinMode uint8
+
 const (
 	PinInput PinMode = iota
 	PinInputPullup
@@ -21,6 +21,8 @@ var (
 	ErrInvalidSPIBus = errors.New("machine: invalid SPI bus")
 )

+type PinMode uint8
+
 const (
 	PinOutput PinMode = iota
 	PinInput
@@ -11,6 +11,8 @@ func CPUFrequency() uint32 {
 	return 80000000 // 80MHz
 }

+type PinMode uint8
+
 const (
 	PinOutput PinMode = iota
 	PinInput
@@ -12,6 +12,8 @@ func CPUFrequency() uint32 {
 	return 16000000
 }

+type PinMode uint8
+
 const (
 	PinInput PinMode = iota
 	PinOutput
@@ -30,6 +30,8 @@ const (
 // Make it easier to directly write to I/O RAM.
 var ioram = (*[0x400]volatile.Register8)(unsafe.Pointer(uintptr(0x04000000)))

+type PinMode uint8
+
 // Set has not been implemented.
 func (p Pin) Set(value bool) {
 	// do nothing
@@ -52,7 +54,7 @@ func (d FramebufDisplay) Size() (x, y int16) {
 }

 func (d FramebufDisplay) SetPixel(x, y int16, c color.RGBA) {
-	d.port[y][x].Set((uint16(c.R) >> 3) | ((uint16(c.G) >> 3) << 5) | ((uint16(c.B) >> 3) << 10))
+	d.port[y][x].Set(uint16(c.R)&0x1f | uint16(c.G)&0x1f<<5 | uint16(c.B)&0x1f<<10)
 }

 func (d FramebufDisplay) Display() error {
@@ -10,6 +10,8 @@ var (
 	UART0 = UART{0}
 )

+type PinMode uint8
+
 const (
 	PinInput PinMode = iota
 	PinOutput
@@ -82,6 +84,24 @@ func (adc ADC) Get() uint16 {
 //export __tinygo_adc_read
 func adcRead(pin Pin) uint16

+// InitPWM enables support for PWM peripherals.
+func InitPWM() {
+	// Nothing to do here.
+}
+
+// Configure configures a PWM pin for output.
+func (pwm PWM) Configure() error {
+	return nil
+}
+
+// Set turns on the duty cycle for a PWM pin using the provided value.
+func (pwm PWM) Set(value uint16) {
+	pwmSet(pwm.Pin, value)
+}
+
+//export __tinygo_pwm_set
+func pwmSet(pin Pin, value uint16)
+
 // I2C is a generic implementation of the Inter-IC communication protocol.
 type I2C struct {
 	Bus uint8
@@ -14,6 +14,7 @@ func CPUFrequency() uint32 {
 	return 390000000
 }

+type PinMode uint8
 type fpioaPullMode uint8
 type PinChange uint8

@@ -15,6 +15,8 @@ func CPUFrequency() uint32 {
 	return 600000000
 }

+type PinMode uint8
+
 const (
 	// GPIO
 	PinInput PinMode = iota
@@ -13,6 +13,8 @@ var (
 	ErrTxInvalidSliceSize = errors.New("SPI write and read slices must be same size")
 )

+type PinMode uint8
+
 const (
 	PinInput         PinMode = (nrf.GPIO_PIN_CNF_DIR_Input << nrf.GPIO_PIN_CNF_DIR_Pos) | (nrf.GPIO_PIN_CNF_INPUT_Connect << nrf.GPIO_PIN_CNF_INPUT_Pos)
 	PinInputPullup   PinMode = PinInput | (nrf.GPIO_PIN_CNF_PULL_Pullup << nrf.GPIO_PIN_CNF_PULL_Pos)
@@ -63,7 +63,7 @@ func (i2c *I2C) setPins(scl, sda Pin) {

 // PWM
 var (
-	PWM0 = &PWM{PWM: nrf.PWM0}
-	PWM1 = &PWM{PWM: nrf.PWM1}
-	PWM2 = &PWM{PWM: nrf.PWM2}
+	pwmChannelPins     = [3]uint32{0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF}
+	pwms               = [3]*nrf.PWM_Type{nrf.PWM0, nrf.PWM1, nrf.PWM2}
+	pwmChannelSequence [3]uint16
 )
@@ -83,8 +83,7 @@ func (i2c *I2C) setPins(scl, sda Pin) {

 // PWM
 var (
-	PWM0 = &PWM{PWM: nrf.PWM0}
-	PWM1 = &PWM{PWM: nrf.PWM1}
-	PWM2 = &PWM{PWM: nrf.PWM2}
-	PWM3 = &PWM{PWM: nrf.PWM3}
+	pwmChannelPins     = [4]uint32{0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF}
+	pwms               = [4]*nrf.PWM_Type{nrf.PWM0, nrf.PWM1, nrf.PWM2, nrf.PWM3}
+	pwmChannelSequence [4]uint16
 )
@@ -79,8 +79,7 @@ func (i2c *I2C) setPins(scl, sda Pin) {

 // PWM
 var (
-	PWM0 = &PWM{PWM: nrf.PWM0}
-	PWM1 = &PWM{PWM: nrf.PWM1}
-	PWM2 = &PWM{PWM: nrf.PWM2}
-	PWM3 = &PWM{PWM: nrf.PWM3}
+	pwmChannelPins     = [4]uint32{0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF}
+	pwms               = [4]*nrf.PWM_Type{nrf.PWM0, nrf.PWM1, nrf.PWM2, nrf.PWM3}
+	pwmChannelSequence [4]uint16
 )
@@ -445,7 +445,7 @@ func handleStandardSetup(setup usbSetup) bool {
 func cdcSetup(setup usbSetup) bool {
 	if setup.bmRequestType == usb_REQUEST_DEVICETOHOST_CLASS_INTERFACE {
 		if setup.bRequest == usb_CDC_GET_LINE_CODING {
-			var b [cdcLineInfoSize]byte
+			b := make([]byte, 7)
 			b[0] = byte(usbLineInfo.dwDTERate)
 			b[1] = byte(usbLineInfo.dwDTERate >> 8)
 			b[2] = byte(usbLineInfo.dwDTERate >> 16)
@@ -454,7 +454,7 @@ func cdcSetup(setup usbSetup) bool {
 			b[5] = byte(usbLineInfo.bParityType)
 			b[6] = byte(usbLineInfo.bDataBits)

-			sendUSBPacket(0, b[:])
+			sendUSBPacket(0, b)
 			return true
 		}
 	}
--- a/Show More
+++ b/Show More