wasm: improve malloc/free heap tracking

Using a slice requires a lot less in code size than a map. This is visible when compiling a very small "hello world" style program. Before tracking memory in malloc/free: 2873 bytes With tracking using a map: 6551 bytes With a slice instead of a map: 3532 bytes Of course, most of this code size increase won't be visible with https://github.com/tinygo-org/tinygo/pull/3142, but it's still a saving of around 3kB in this minimal example.
tests: do not cast pointers to uintptr
2026-07-27 07:08:42 +00:00 · 2022-09-30 14:28:54 +02:00 · 2022-09-30 14:28:54 +02:00
116 changed files with 543 additions and 948 deletions
@@ -118,7 +118,13 @@ jobs:
    steps:
      - test-linux:
          llvm: "14"
-    resource_class: large
+  test-llvm14-go119:
+    docker:
+      - image: golang:1.19beta1-buster
+    steps:
+      - test-linux:
+          llvm: "14"
+          fmt-check: false

 workflows:
  test-all:
@@ -126,3 +132,6 @@ workflows:
      # This tests our lowest supported versions of Go and LLVM, to make sure at
      # least the smoke tests still pass.
      - test-llvm14-go118
+      # This tests a beta version of Go. It should be removed once regular
+      # release builds are built using this version.
+      - test-llvm14-go119
@@ -34,7 +34,7 @@ jobs:
      - name: Install Go
        uses: actions/setup-go@v3
        with:
-          go-version: '1.19'
+          go-version: '1.18.1'
          cache: true
      - name: Cache LLVM source
        uses: actions/cache@v3
@@ -114,7 +114,7 @@ jobs:
      - name: Install Go
        uses: actions/setup-go@v3
        with:
-          go-version: '1.19'
+          go-version: '1.18'
          cache: true
      - name: Build TinyGo
        run: go install
@@ -18,7 +18,7 @@ jobs:
    # statically linked binary.
    runs-on: ubuntu-latest
    container:
-      image: golang:1.19-alpine
+      image: golang:1.18-alpine
    steps:
      - name: Install apk dependencies
        # tar: needed for actions/cache@v3
@@ -118,7 +118,7 @@ jobs:
      - name: Install Go
        uses: actions/setup-go@v3
        with:
-          go-version: '1.19'
+          go-version: '1.18.1'
          cache: true
      - name: Install wasmtime
        run: |
@@ -171,7 +171,7 @@ jobs:
      - name: Install Go
        uses: actions/setup-go@v3
        with:
-          go-version: '1.19'
+          go-version: '1.18.1'
          cache: true
      - name: Install Node.js
        uses: actions/setup-node@v2
@@ -271,7 +271,7 @@ jobs:
      - name: Install Go
        uses: actions/setup-go@v3
        with:
-          go-version: '1.19'
+          go-version: '1.18.1'
          cache: true
      - name: Cache LLVM source
        uses: actions/cache@v3
@@ -371,7 +371,7 @@ jobs:
      - name: Install Go
        uses: actions/setup-go@v3
        with:
-          go-version: '1.19'
+          go-version: '1.18.1'
          cache: true
      - name: Cache LLVM source
        uses: actions/cache@v3
@@ -29,7 +29,7 @@ jobs:
      - name: Install Go
        uses: actions/setup-go@v3
        with:
-          go-version: '1.19'
+          go-version: '1.18.1'
          cache: true
      - name: Cache LLVM source
        uses: actions/cache@v3
@@ -1,87 +1,3 @@
-0.26.0
---
-
-* **general**
-  - remove support for LLVM 13
-  - remove calls to deprecated ioutil package
-  - move from `os.IsFoo` to `errors.Is(err, ErrFoo)`
-  - fix for builds using an Android host
-  - make interp timeout configurable from command line
-  - ignore ports with VID/PID if there is no candidates
-  - drop support for Go 1.16 and Go 1.17
-  - update serial package to v1.3.5 for latest bugfixes
-  - remove GOARM from `tinygo info`
-  - add flag for setting the goroutine stack size
-  - add serial port monitoring functionality
-* **compiler**
-  - `cgo`: implement support for static functions
-  - `cgo`: fix panic when FuncType.Results is nil
-  - `compiler`: add aliases for `edwards25519/field.feMul` and `field.feSquare`
-  - `compiler`: fix incorrect DWARF type in some generic parameters
-  - `compiler`: use LLVM math builtins everywhere
-  - `compiler`: replace some math operation bodies with LLVM intrinsics
-  - `compiler`: replace math aliases with intrinsics
-  - `compiler`: fix `unsafe.Sizeof` for chan and map values
-  - `compileopts`: use tags parser from buildutil
-  - `compileopts`: use backticks for regexp to avoid extra escapes
-  - `compileopts`: fail fast on duplicate values in target field slices
-  - `compileopts`: fix windows/arm target triple
-  - `compileopts`: improve error handling when loading target/*.json
-  - `compileopts`: add support for stlink-dap programmer
-  - `compileopts`: do not complain about `-no-debug` on MacOS
-  - `goenv`: support `GOOS=android`
-  - `interp`: fix reading from external global
-  - `loader`: fix link error for `crypto/internal/boring/sig.StandardCrypto`
-* **standard library**
-  - rename assembly files to .S extension
-  - `machine`: add PWM peripheral comments to pins
-  - `machine`: improve UARTParity slightly
-  - `machine`: do not export DFU_MAGIC_* constants on nrf52840
-  - `machine`: rename `PinInputPullUp`/`PinInputPullDown`
-  - `machine`: add `KHz`, `MHz`, `GHz` constants, deprecate `TWI_FREQ_*` constants
-  - `machine`: remove level triggered pin interrupts
-  - `machine`: do not expose `RESET_MAGIC_VALUE`
-  - `machine`: use `NoPin` constant where appropriate (instead of `0` for example)
-  - `net`: sync net.go with Go 1.18 stdlib
-  - `os`: add `SyscallError.Timeout`
-  - `os`: add `ErrProcessDone` error
-  - `reflect`: implement `CanInterface` and fix string `Index`
-  - `runtime`: make `MemStats` available to leaking collector
-  - `runtime`: add `MemStats.TotalAlloc`
-  - `runtime`: add `MemStats.Mallocs` and `Frees`
-  - `runtime`: add support for `time.NewTimer` and `time.NewTicker`
-  - `runtime`: implement `resetTimer`
-  - `runtime`: ensure some headroom for the GC to run
-  - `runtime`: make gc and scheduler asserts settable with build tags
-  - `runtime/pprof`: add `WriteHeapProfile`
-  - `runtime/pprof`: `runtime/trace`: stub some additional functions
-  - `sync`: implement `Map.LoadAndDelete`
-  - `syscall`: group WASI consts by purpose
-  - `syscall`: add WASI `{D,R}SYNC`, `NONBLOCK` FD flags
-  - `syscall`: add ENOTCONN on darwin
-  - `testing`: add support for -benchmem
-* **targets**
-  - remove USB vid/pid pair of bootloader
-  - `esp32c3`: remove unused `UARTStopBits` constants
-  - `nrf`: implement `GetRNG` function
-  - `nrf`: `rp2040`: add `machine.ReadTemperature`
-  - `nrf52`: cleanup s140v6 and s140v7 uf2 targets
-  - `rp2040`: implement semi-random RNG based on ROSC based on pico-sdk
-  - `wasm`: add summary of wasm examples and fix callback bug
-  - `wasm`: do not allow undefined symbols (`--allow-undefined`)
-  - `wasm`: make sure buffers returned by `malloc` are kept until `free` is called
-  - `windows`: save and restore xmm registers when switching goroutines
-* **boards**
-  - add Pimoroni's Tufty2040
-  - add XIAO ESP32C3
-  - add Adafruit QT2040
-  - add Adafruit QT Py RP2040
-  - `esp32c3-12f`: `matrixportal-m4`: `p1am-100`: remove duplicate build tags
-  - `hifive1-qemu`: remove this emulated board
-  - `wioterminal`: add UART3 for RTL8720DN
-  - `xiao-ble`: fix usbpid
-
-
 0.25.0
 ---

@@ -1,5 +1,5 @@
 # tinygo-llvm stage obtains the llvm source for TinyGo
-FROM golang:1.19 AS tinygo-llvm
+FROM golang:1.18 AS tinygo-llvm

 RUN apt-get update && \
    apt-get install -y apt-utils make cmake clang-11 binutils-avr gcc-avr avr-libc ninja-build
@@ -330,6 +330,7 @@ endif
 # compress/lzw appears to hang on wasi
 # crypto/hmac fails on wasi, it exits with a "slice out of range" panic
 # debug/plan9obj requires os.ReadAt, which is not yet supported on windows
+# io/fs requires os.ReadDir, which is not yet supported on windows or wasi
 # io/ioutil requires os.ReadDir, which is not yet supported on windows or wasi
 # strconv requires recover() which is not yet supported on wasi
 # text/template/parse requires recover(), which is not yet supported on wasi
@@ -343,6 +344,7 @@ TEST_PACKAGES_LINUX := \
 	crypto/hmac \
 	debug/dwarf \
 	debug/plan9obj \
+	io/fs \
 	io/ioutil \
 	strconv \
 	testing/fstest \
@@ -371,15 +373,12 @@ report-stdlib-tests-pass:
 # Standard library packages that pass tests quickly on the current platform
 ifeq ($(shell uname),Darwin)
 TEST_PACKAGES_HOST := $(TEST_PACKAGES_FAST) $(TEST_PACKAGES_DARWIN)
-TEST_IOFS := true
 endif
 ifeq ($(shell uname),Linux)
 TEST_PACKAGES_HOST := $(TEST_PACKAGES_FAST) $(TEST_PACKAGES_LINUX)
-TEST_IOFS := true
 endif
 ifeq ($(OS),Windows_NT)
 TEST_PACKAGES_HOST := $(TEST_PACKAGES_FAST) $(TEST_PACKAGES_WINDOWS)
-TEST_IOFS := false
 endif

 # Test known-working standard library packages.
@@ -387,12 +386,6 @@ endif
 .PHONY: tinygo-test
 tinygo-test:
 	$(TINYGO) test $(TEST_PACKAGES_HOST) $(TEST_PACKAGES_SLOW)
-	@# io/fs requires os.ReadDir, not yet supported on windows or wasi. It also
-	@# requires a large stack-size. Hence, io/fs is only run conditionally.
-	@# For more details, see the comments on issue #3143.
-ifeq ($(TEST_IOFS),true)
-	$(TINYGO) test -stack-size=6MB io/fs
-endif
 tinygo-test-fast:
 	$(TINYGO) test $(TEST_PACKAGES_HOST)
 tinygo-bench:
@@ -618,7 +611,7 @@ endif
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=challenger-rp2040    examples/blinky1
 	@$(MD5SUM) test.hex
-	$(TINYGO) build -size short -o test.hex -target=trinkey-qt2040      examples/temp
+	$(TINYGO) build -size short -o test.hex -target=trinkey-qt2040      examples/adc_rp2040
 	@$(MD5SUM) test.hex
 	# test pwm
 	$(TINYGO) build -size short -o test.hex -target=itsybitsy-m0        examples/pwm
@@ -178,7 +178,7 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil

 		Scheduler:          config.Scheduler(),
 		AutomaticStackSize: config.AutomaticStackSize(),
-		DefaultStackSize:   config.StackSize(),
+		DefaultStackSize:   config.Target.DefaultStackSize,
 		NeedsStackObjects:  config.NeedsStackObjects(),
 		Debug:              true,
 	}
@@ -700,18 +700,21 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 	// Add embedded files.
 	linkerDependencies = append(linkerDependencies, embedFileObjects...)

-	// Determine whether the compilation configuration would result in debug
-	// (DWARF) information in the object files.
-	var hasDebug = true
-	if config.GOOS() == "darwin" {
-		// Debug information isn't stored in the binary itself on MacOS but
-		// is left in the object files by default. The binary does store the
-		// path to these object files though.
-		hasDebug = false
-	}
-
 	// Strip debug information with -no-debug.
-	if hasDebug && !config.Debug() {
+	if !config.Debug() {
+		for _, tag := range config.BuildTags() {
+			if tag == "baremetal" {
+				// Don't use -no-debug on baremetal targets. It makes no sense:
+				// the debug information isn't flashed to the device anyway.
+				return fmt.Errorf("stripping debug information is unnecessary for baremetal targets")
+			}
+		}
+		if config.GOOS() == "darwin" {
+			// Debug information isn't stored in the binary itself on MacOS but
+			// is left in the object files by default. The binary does store the
+			// path to these object files though.
+			return errors.New("cannot remove debug information: MacOS doesn't store debug info in the executable by default")
+		}
 		if config.Target.Linker == "wasm-ld" {
 			// Don't just strip debug information, also compress relocations
 			// while we're at it. Relocations can only be compressed when debug
@@ -32,7 +32,6 @@ type cgoPackage struct {
 	errors          []error
 	currentDir      string // current working directory
 	packageDir      string // full path to the package to process
-	importPath      string
 	fset            *token.FileSet
 	tokenFiles      map[string]*token.File
 	definedGlobally map[string]ast.Node
@@ -40,15 +39,12 @@ type cgoPackage struct {
 	cflags          []string // CFlags from #cgo lines
 	ldflags         []string // LDFlags from #cgo lines
 	visitedFiles    map[string][]byte
-	cgoHeaders      []string
 }

 // cgoFile holds information only for a single Go file (with one or more
 // `import "C"` statements).
 type cgoFile struct {
 	*cgoPackage
-	file    *ast.File
-	index   int
 	defined map[string]ast.Node
 	names   map[string]clangCursor
 }
@@ -162,10 +158,9 @@ func GoBytes(ptr unsafe.Pointer, length C.int) []byte {
 // functions), the CFLAGS and LDFLAGS found in #cgo lines, and a map of file
 // hashes of the accessed C header files. If there is one or more error, it
 // returns these in the []error slice but still modifies the AST.
-func Process(files []*ast.File, dir, importPath string, fset *token.FileSet, cflags []string, clangHeaders string) (*ast.File, []string, []string, []string, map[string][]byte, []error) {
+func Process(files []*ast.File, dir string, fset *token.FileSet, cflags []string, clangHeaders string) (*ast.File, []string, []string, []string, map[string][]byte, []error) {
 	p := &cgoPackage{
 		currentDir:      dir,
-		importPath:      importPath,
 		fset:            fset,
 		tokenFiles:      map[string]*token.File{},
 		definedGlobally: map[string]ast.Node{},
@@ -215,13 +210,13 @@ func Process(files []*ast.File, dir, importPath string, fset *token.FileSet, cfl
 		}
 	}
 	// Patch some types, for example *C.char in C.CString.
-	cf := p.newCGoFile(nil, -1) // dummy *cgoFile for the walker
+	cf := p.newCGoFile()
 	astutil.Apply(p.generated, func(cursor *astutil.Cursor) bool {
 		return cf.walker(cursor, nil)
 	}, nil)

 	// Find `import "C"` C fragments in the file.
-	p.cgoHeaders = make([]string, len(files)) // combined CGo header fragment for each file
+	cgoHeaders := make([]string, len(files)) // combined CGo header fragment for each file
 	for i, f := range files {
 		var cgoHeader string
 		for i := 0; i < len(f.Decls); i++ {
@@ -280,7 +275,7 @@ func Process(files []*ast.File, dir, importPath string, fset *token.FileSet, cfl
 			cgoHeader += fragment
 		}

-		p.cgoHeaders[i] = cgoHeader
+		cgoHeaders[i] = cgoHeader
 	}

 	// Define CFlags that will be used while parsing the package.
@@ -294,7 +289,7 @@ func Process(files []*ast.File, dir, importPath string, fset *token.FileSet, cfl
 	}

 	// Retrieve types such as C.int, C.longlong, etc from C.
-	p.newCGoFile(nil, -1).readNames(builtinAliasTypedefs, cflagsForCGo, "", func(names map[string]clangCursor) {
+	p.newCGoFile().readNames(builtinAliasTypedefs, cflagsForCGo, "", func(names map[string]clangCursor) {
 		gen := &ast.GenDecl{
 			TokPos: token.NoPos,
 			Tok:    token.TYPE,
@@ -308,8 +303,8 @@ func Process(files []*ast.File, dir, importPath string, fset *token.FileSet, cfl

 	// Process CGo imports for each file.
 	for i, f := range files {
-		cf := p.newCGoFile(f, i)
-		cf.readNames(p.cgoHeaders[i], cflagsForCGo, filepath.Base(fset.File(f.Pos()).Name()), func(names map[string]clangCursor) {
+		cf := p.newCGoFile()
+		cf.readNames(cgoHeaders[i], cflagsForCGo, filepath.Base(fset.File(f.Pos()).Name()), func(names map[string]clangCursor) {
 			for _, name := range builtinAliases {
 				// Names such as C.int should not be obtained from C.
 				// This works around an issue in picolibc that has `#define int`
@@ -325,14 +320,12 @@ func Process(files []*ast.File, dir, importPath string, fset *token.FileSet, cfl
 	// Print the newly generated in-memory AST, for debugging.
 	//ast.Print(fset, p.generated)

-	return p.generated, p.cgoHeaders, p.cflags, p.ldflags, p.visitedFiles, p.errors
+	return p.generated, cgoHeaders, p.cflags, p.ldflags, p.visitedFiles, p.errors
 }

-func (p *cgoPackage) newCGoFile(file *ast.File, index int) *cgoFile {
+func (p *cgoPackage) newCGoFile() *cgoFile {
 	return &cgoFile{
 		cgoPackage: p,
-		file:       file,
-		index:      index,
 		defined:    make(map[string]ast.Node),
 		names:      make(map[string]clangCursor),
 	}
@@ -948,9 +941,6 @@ func (p *cgoPackage) isEquivalentAST(a, b ast.Node) bool {
 		if !ok {
 			return false
 		}
-		if node == nil || b == nil {
-			return node == b
-		}
 		if len(node.List) != len(b.List) {
 			return false
 		}
@@ -1127,11 +1117,8 @@ func (f *cgoFile) getASTDeclName(name string, found clangCursor, iscall bool) st
 		return alias
 	}
 	node := f.getASTDeclNode(name, found, iscall)
-	if node, ok := node.(*ast.FuncDecl); ok {
-		if !iscall {
-			return node.Name.Name + "$funcaddr"
-		}
-		return node.Name.Name
+	if _, ok := node.(*ast.FuncDecl); ok && !iscall {
+		return "C." + name + "$funcaddr"
 	}
 	return "C." + name
 }
@@ -1155,7 +1142,7 @@ func (f *cgoFile) getASTDeclNode(name string, found clangCursor, iscall bool) as
 			// Original cgo reports an error like
 			//   cgo: inconsistent definitions for C.myint
 			// which is far less helpful.
-			f.addError(getPos(node), name+" defined previously at "+f.fset.Position(getPos(newNode)).String()+" with a different type")
+			f.addError(getPos(node), "defined previously at "+f.fset.Position(getPos(newNode)).String()+" with a different type")
 		}
 		f.defined[name] = node
 		return node
@@ -1163,39 +1150,11 @@ func (f *cgoFile) getASTDeclNode(name string, found clangCursor, iscall bool) as

 	// The declaration has no AST node. Create it now.
 	f.defined[name] = nil
-	node, extra := f.createASTNode(name, found)
+	node, elaboratedType := f.createASTNode(name, found)
 	f.defined[name] = node
+	f.definedGlobally[name] = node
 	switch node := node.(type) {
 	case *ast.FuncDecl:
-		if strings.HasPrefix(node.Doc.List[0].Text, "//export _Cgo_static_") {
-			// Static function. Only accessible in the current Go file.
-			globalName := strings.TrimPrefix(node.Doc.List[0].Text, "//export ")
-			// Make an alias. Normally this is done using the alias function
-			// attribute, but MacOS for some reason doesn't support this (even
-			// though the linker has support for aliases in the form of N_INDR).
-			// Therefore, create an actual function for MacOS.
-			var params []string
-			for _, param := range node.Type.Params.List {
-				params = append(params, param.Names[0].Name)
-			}
-			callInst := fmt.Sprintf("%s(%s);", name, strings.Join(params, ", "))
-			if node.Type.Results != nil {
-				callInst = "return " + callInst
-			}
-			aliasDeclaration := fmt.Sprintf(`
-#ifdef __APPLE__
-%s {
-	%s
-}
-#else
-extern __typeof(%s) %s __attribute__((alias(%#v)));
-#endif
-`, extra.(string), callInst, name, globalName, name)
-			f.cgoHeaders[f.index] += "\n\n" + aliasDeclaration
-		} else {
-			// Regular (non-static) function.
-			f.definedGlobally[name] = node
-		}
 		f.generated.Decls = append(f.generated.Decls, node)
 		// Also add a declaration like the following:
 		//   var C.foo$funcaddr unsafe.Pointer
@@ -1203,7 +1162,7 @@ extern __typeof(%s) %s __attribute__((alias(%#v)));
 			Tok: token.VAR,
 			Specs: []ast.Spec{
 				&ast.ValueSpec{
-					Names: []*ast.Ident{{Name: node.Name.Name + "$funcaddr"}},
+					Names: []*ast.Ident{{Name: "C." + name + "$funcaddr"}},
 					Type: &ast.SelectorExpr{
 						X:   &ast.Ident{Name: "unsafe"},
 						Sel: &ast.Ident{Name: "Pointer"},
@@ -1212,10 +1171,8 @@ extern __typeof(%s) %s __attribute__((alias(%#v)));
 			},
 		})
 	case *ast.GenDecl:
-		f.definedGlobally[name] = node
 		f.generated.Decls = append(f.generated.Decls, node)
 	case *ast.TypeSpec:
-		f.definedGlobally[name] = node
 		f.generated.Decls = append(f.generated.Decls, &ast.GenDecl{
 			Tok:   token.TYPE,
 			Specs: []ast.Spec{node},
@@ -1229,8 +1186,7 @@ extern __typeof(%s) %s __attribute__((alias(%#v)));

 	// If this is a struct or union it may need bitfields or union accessor
 	// methods.
-	switch elaboratedType := extra.(type) {
-	case *elaboratedTypeInfo:
+	if elaboratedType != nil {
 		// Add struct bitfields.
 		for _, bitfield := range elaboratedType.bitfields {
 			f.createBitfieldGetter(bitfield, "C."+name)
@@ -48,7 +48,7 @@ func TestCGo(t *testing.T) {
 			}

 			// Process the AST with CGo.
-			cgoAST, _, _, _, _, cgoErrors := Process([]*ast.File{f}, "testdata", "main", fset, cflags, "")
+			cgoAST, _, _, _, _, cgoErrors := Process([]*ast.File{f}, "testdata", fset, cflags, "")

 			// Check the AST for type errors.
 			var typecheckErrors []error
@@ -115,84 +115,6 @@ func TestCGo(t *testing.T) {
 	}
 }

-func Test_cgoPackage_isEquivalentAST(t *testing.T) {
-	fieldA := &ast.Field{Type: &ast.BasicLit{Kind: token.STRING, Value: "a"}}
-	fieldB := &ast.Field{Type: &ast.BasicLit{Kind: token.STRING, Value: "b"}}
-	listOfFieldA := &ast.FieldList{List: []*ast.Field{fieldA}}
-	listOfFieldB := &ast.FieldList{List: []*ast.Field{fieldB}}
-	funcDeclA := &ast.FuncDecl{Name: &ast.Ident{Name: "a"}, Type: &ast.FuncType{Params: &ast.FieldList{}, Results: listOfFieldA}}
-	funcDeclB := &ast.FuncDecl{Name: &ast.Ident{Name: "b"}, Type: &ast.FuncType{Params: &ast.FieldList{}, Results: listOfFieldB}}
-	funcDeclNoResults := &ast.FuncDecl{Name: &ast.Ident{Name: "C"}, Type: &ast.FuncType{Params: &ast.FieldList{}}}
-
-	testCases := []struct {
-		name     string
-		a, b     ast.Node
-		expected bool
-	}{
-		{
-			name:     "both nil",
-			expected: true,
-		},
-		{
-			name:     "not same type",
-			a:        fieldA,
-			b:        &ast.FuncDecl{},
-			expected: false,
-		},
-		{
-			name:     "Field same",
-			a:        fieldA,
-			b:        fieldA,
-			expected: true,
-		},
-		{
-			name:     "Field different",
-			a:        fieldA,
-			b:        fieldB,
-			expected: false,
-		},
-		{
-			name:     "FuncDecl Type Results nil",
-			a:        funcDeclNoResults,
-			b:        funcDeclNoResults,
-			expected: true,
-		},
-		{
-			name:     "FuncDecl Type Results same",
-			a:        funcDeclA,
-			b:        funcDeclA,
-			expected: true,
-		},
-		{
-			name:     "FuncDecl Type Results different",
-			a:        funcDeclA,
-			b:        funcDeclB,
-			expected: false,
-		},
-		{
-			name:     "FuncDecl Type Results a nil",
-			a:        funcDeclNoResults,
-			b:        funcDeclB,
-			expected: false,
-		},
-		{
-			name:     "FuncDecl Type Results b nil",
-			a:        funcDeclA,
-			b:        funcDeclNoResults,
-			expected: false,
-		},
-	}
-
-	for _, tc := range testCases {
-		t.Run(tc.name, func(t *testing.T) {
-			p := &cgoPackage{}
-			if got := p.isEquivalentAST(tc.a, tc.b); tc.expected != got {
-				t.Errorf("expected %v, got %v", tc.expected, got)
-			}
-		})
-	}
-}
-
 // simpleImporter implements the types.Importer interface, but only allows
 // importing the unsafe package.
 type simpleImporter struct {
@@ -4,9 +4,7 @@ package cgo
 // modification. It does not touch the AST itself.

 import (
-	"crypto/sha256"
 	"crypto/sha512"
-	"encoding/hex"
 	"fmt"
 	"go/ast"
 	"go/scanner"
@@ -45,8 +43,6 @@ typedef struct {
 GoCXCursor tinygo_clang_getTranslationUnitCursor(CXTranslationUnit tu);
 unsigned tinygo_clang_visitChildren(GoCXCursor parent, CXCursorVisitor visitor, CXClientData client_data);
 CXString tinygo_clang_getCursorSpelling(GoCXCursor c);
-CXString tinygo_clang_getCursorPrettyPrinted(GoCXCursor c, CXPrintingPolicy Policy);
-CXPrintingPolicy tinygo_clang_getCursorPrintingPolicy(GoCXCursor c);
 enum CXCursorKind tinygo_clang_getCursorKind(GoCXCursor c);
 CXType tinygo_clang_getCursorType(GoCXCursor c);
 GoCXCursor tinygo_clang_getTypeDeclaration(CXType t);
@@ -54,7 +50,6 @@ CXType tinygo_clang_getTypedefDeclUnderlyingType(GoCXCursor c);
 CXType tinygo_clang_getCursorResultType(GoCXCursor c);
 int tinygo_clang_Cursor_getNumArguments(GoCXCursor c);
 GoCXCursor tinygo_clang_Cursor_getArgument(GoCXCursor c, unsigned i);
-enum CX_StorageClass tinygo_clang_Cursor_getStorageClass(GoCXCursor c);
 CXSourceLocation tinygo_clang_getCursorLocation(GoCXCursor c);
 CXSourceRange tinygo_clang_getCursorExtent(GoCXCursor c);
 CXTranslationUnit tinygo_clang_Cursor_getTranslationUnit(GoCXCursor c);
@@ -194,7 +189,7 @@ func (f *cgoFile) readNames(fragment string, cflags []string, filename string, c

 // Convert the AST node under the given Clang cursor to a Go AST node and return
 // it.
-func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
+func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, *elaboratedTypeInfo) {
 	kind := C.tinygo_clang_getCursorKind(c)
 	pos := f.getCursorPosition(c)
 	switch kind {
@@ -205,43 +200,19 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 			Kind: ast.Fun,
 			Name: "C." + name,
 		}
-		exportName := name
-		localName := name
-		var stringSignature string
-		if C.tinygo_clang_Cursor_getStorageClass(c) == C.CX_SC_Static {
-			// A static function is assigned a globally unique symbol name based
-			// on the file path (like _Cgo_static_2d09198adbf58f4f4655_foo) and
-			// has a different Go name in the form of C.foo!symbols.go instead
-			// of just C.foo.
-			path := f.importPath + "/" + filepath.Base(f.fset.File(f.file.Pos()).Name())
-			staticIDBuf := sha256.Sum256([]byte(path))
-			staticID := hex.EncodeToString(staticIDBuf[:10])
-			exportName = "_Cgo_static_" + staticID + "_" + name
-			localName = name + "!" + filepath.Base(path)
-
-			// Create a signature. This is necessary for MacOS to forward the
-			// call, because MacOS doesn't support aliases like ELF and PE do.
-			// (There is N_INDR but __attribute__((alias("..."))) doesn't work).
-			policy := C.tinygo_clang_getCursorPrintingPolicy(c)
-			defer C.clang_PrintingPolicy_dispose(policy)
-			C.clang_PrintingPolicy_setProperty(policy, C.CXPrintingPolicy_TerseOutput, 1)
-			stringSignature = getString(C.tinygo_clang_getCursorPrettyPrinted(c, policy))
-			stringSignature = strings.Replace(stringSignature, " "+name+"(", " "+exportName+"(", 1)
-			stringSignature = strings.TrimPrefix(stringSignature, "static ")
-		}
 		args := make([]*ast.Field, numArgs)
 		decl := &ast.FuncDecl{
 			Doc: &ast.CommentGroup{
 				List: []*ast.Comment{
 					{
 						Slash: pos - 1,
-						Text:  "//export " + exportName,
+						Text:  "//export " + name,
 					},
 				},
 			},
 			Name: &ast.Ident{
 				NamePos: pos,
-				Name:    "C." + localName,
+				Name:    "C." + name,
 				Obj:     obj,
 			},
 			Type: &ast.FuncType{
@@ -292,7 +263,7 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 			}
 		}
 		obj.Decl = decl
-		return decl, stringSignature
+		return decl, nil
 	case C.CXCursor_StructDecl, C.CXCursor_UnionDecl:
 		typ := f.makeASTRecordType(c, pos)
 		typeName := "C." + name
@@ -17,14 +17,6 @@ CXString tinygo_clang_getCursorSpelling(CXCursor c) {
 	return clang_getCursorSpelling(c);
 }

-CXString tinygo_clang_getCursorPrettyPrinted(CXCursor c, CXPrintingPolicy policy) {
-	return clang_getCursorPrettyPrinted(c, policy);
-}
-
-CXPrintingPolicy tinygo_clang_getCursorPrintingPolicy(CXCursor c) {
-	return clang_getCursorPrintingPolicy(c);
-}
-
 enum CXCursorKind tinygo_clang_getCursorKind(CXCursor c) {
 	return clang_getCursorKind(c);
 }
@@ -53,10 +45,6 @@ CXCursor tinygo_clang_Cursor_getArgument(CXCursor c, unsigned i) {
 	return clang_Cursor_getArgument(c, i);
 }

-enum CX_StorageClass tinygo_clang_Cursor_getStorageClass(CXCursor c) {
-	return clang_Cursor_getStorageClass(c);
-}
-
 CXSourceLocation tinygo_clang_getCursorLocation(CXCursor c) {
 	return clang_getCursorLocation(c);
 }
@@ -5,7 +5,6 @@ package main
 int foo(int a, int b);
 void variadic0();
 void variadic2(int x, int y, ...);
-static void staticfunc(int x);

 // Global variable signatures.
 extern int someValue;
@@ -17,7 +16,6 @@ func accessFunctions() {
 	C.foo(3, 4)
 	C.variadic0()
 	C.variadic2(3, 5)
-	C.staticfunc(3)
 }

 func accessGlobals() {
@@ -55,10 +55,5 @@ func C.variadic2(x C.int, y C.int)

 var C.variadic2$funcaddr unsafe.Pointer

-//export _Cgo_static_173c95a79b6df1980521_staticfunc
-func C.staticfunc!symbols.go(x C.int)
-
-var C.staticfunc!symbols.go$funcaddr unsafe.Pointer
-
 //go:extern someValue
 var C.someValue C.int
@@ -175,15 +175,6 @@ func (c *Config) AutomaticStackSize() bool {
 	return false
 }

-// StackSize returns the default stack size to be used for goroutines, if the
-// stack size could not be determined automatically at compile time.
-func (c *Config) StackSize() uint64 {
-	if c.Options.StackSize != 0 {
-		return c.Options.StackSize
-	}
-	return c.Target.DefaultStackSize
-}
-
 // UseThinLTO returns whether ThinLTO should be used for the given target. Some
 // targets (such as wasm) are not yet supported.
 // We should try and remove as many exceptions as possible in the future, so
@@ -377,8 +368,8 @@ func (c *Config) VerifyIR() bool {
 }

 // Debug returns whether debug (DWARF) information should be retained by the
-// linker. By default, debug information is retained, but it can be removed
-// with the -no-debug flag.
+// linker. By default, debug information is retained but it can be removed with
+// the -no-debug flag.
 func (c *Config) Debug() bool {
 	return c.Options.Debug
 }
@@ -28,7 +28,6 @@ type Options struct {
 	GC              string
 	PanicStrategy   string
 	Scheduler       string
-	StackSize       uint64 // goroutine stack size (if none could be automatically determined)
 	Serial          string
 	Work            bool // -work flag to print temporary build directory
 	InterpTimeout   time.Duration
@@ -50,8 +49,6 @@ type Options struct {
 	LLVMFeatures    string
 	Directory       string
 	PrintJSON       bool
-	Monitor         bool
-	BaudRate        int
 }

 // Verify performs a validation on the given options, raising an error if options are not valid.
@@ -79,7 +79,7 @@ func TestCompiler(t *testing.T) {
 				RelocationModel:    config.RelocationModel(),
 				Scheduler:          config.Scheduler(),
 				AutomaticStackSize: config.AutomaticStackSize(),
-				DefaultStackSize:   config.StackSize(),
+				DefaultStackSize:   config.Target.DefaultStackSize,
 				NeedsStackObjects:  config.NeedsStackObjects(),
 			}
 			machine, err := NewTargetMachine(compilerConfig)
@@ -9,10 +9,8 @@ require (
 	github.com/chromedp/chromedp v0.7.6
 	github.com/gofrs/flock v0.8.1
 	github.com/google/shlex v0.0.0-20181106134648-c34317bd91bf
-	github.com/inhies/go-bytesize v0.0.0-20220417184213-4913239db9cf
 	github.com/marcinbor85/gohex v0.0.0-20200531091804-343a4b548892
 	github.com/mattn/go-colorable v0.1.8
-	github.com/mattn/go-tty v0.0.4
 	go.bug.st/serial v1.3.5
 	golang.org/x/sys v0.0.0-20220829200755-d48e67d00261
 	golang.org/x/tools v0.1.11
@@ -12,6 +12,7 @@ github.com/chromedp/sysutil v1.0.0/go.mod h1:kgWmDdq8fTzXYcKIBqIYvRRTnYb9aNS9moA
 github.com/creack/goselect v0.1.2 h1:2DNy14+JPjRBgPzAd1thbQp4BSIihxcBf0IXhQXDRa0=
 github.com/creack/goselect v0.1.2/go.mod h1:a/NhLweNvqIYMuxcMOuWY516Cimucms3DglDzQP3hKY=
 github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/gobwas/httphead v0.1.0 h1:exrUm0f4YX0L7EBwZHuCF4GDp8aJfVeBrlLQrs6NqWU=
 github.com/gobwas/httphead v0.1.0/go.mod h1:O/RXo79gxV8G+RqlR/otEwx4Q36zl9rqC5u12GKvMCM=
 github.com/gobwas/pool v0.2.1 h1:xfeeEhW7pwmX8nuLVlqbzVc7udMDrwetjEv+TZIz1og=
@@ -22,47 +23,44 @@ github.com/gofrs/flock v0.8.1 h1:+gYjHKf32LDeiEEFhQaotPbLuUXjY5ZqxKgXy7n59aw=
 github.com/gofrs/flock v0.8.1/go.mod h1:F1TvTiK9OcQqauNUHlbJvyl9Qa1QvF/gOUDKA14jxHU=
 github.com/google/shlex v0.0.0-20181106134648-c34317bd91bf h1:7+FW5aGwISbqUtkfmIpZJGRgNFg2ioYPvFaUxdqpDsg=
 github.com/google/shlex v0.0.0-20181106134648-c34317bd91bf/go.mod h1:RpwtwJQFrIEPstU94h88MWPXP2ektJZ8cZ0YntAmXiE=
-github.com/inhies/go-bytesize v0.0.0-20220417184213-4913239db9cf h1:FtEj8sfIcaaBfAKrE1Cwb61YDtYq9JxChK1c7AKce7s=
-github.com/inhies/go-bytesize v0.0.0-20220417184213-4913239db9cf/go.mod h1:yrqSXGoD/4EKfF26AOGzscPOgTTJcyAwM2rpixWT+t4=
 github.com/josharian/intern v1.0.0 h1:vlS4z54oSdjm0bgjRigI+G1HpF+tI+9rE5LLzOg8HmY=
 github.com/josharian/intern v1.0.0/go.mod h1:5DoeVV0s6jJacbCEi61lwdGj/aVlrQvzHFFd8Hwg//Y=
 github.com/mailru/easyjson v0.7.7 h1:UGYAvKxe3sBsEDzO8ZeWOSlIQfWFlxbzLZe7hwFURr0=
 github.com/mailru/easyjson v0.7.7/go.mod h1:xzfreul335JAWq5oZzymOObrkdz5UnU4kGfJJLY9Nlc=
 github.com/marcinbor85/gohex v0.0.0-20200531091804-343a4b548892 h1:6J+qramlHVLmiBOgRiBOnQkno8uprqG6YFFQTt6uYIw=
 github.com/marcinbor85/gohex v0.0.0-20200531091804-343a4b548892/go.mod h1:Pb6XcsXyropB9LNHhnqaknG/vEwYztLkQzVCHv8sQ3M=
-github.com/mattn/go-colorable v0.1.4/go.mod h1:U0ppj6V5qS13XJ6of8GYAs25YV2eR4EVcfRqFIhoBtE=
 github.com/mattn/go-colorable v0.1.8 h1:c1ghPdyEDarC70ftn0y+A/Ee++9zz8ljHG1b13eJ0s8=
 github.com/mattn/go-colorable v0.1.8/go.mod h1:u6P/XSegPjTcexA+o6vUJrdnUu04hMope9wVRipJSqc=
-github.com/mattn/go-isatty v0.0.8/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hdxcsrc5s=
-github.com/mattn/go-isatty v0.0.10/go.mod h1:qgIWMr58cqv1PHHyhnkY9lrL7etaEgOFcMEpPG5Rm84=
 github.com/mattn/go-isatty v0.0.12 h1:wuysRhFDzyxgEmMf5xjvJ2M9dZoWAXNNr5LSBS7uHXY=
 github.com/mattn/go-isatty v0.0.12/go.mod h1:cbi8OIDigv2wuxKPP5vlRcQ1OAZbq2CE4Kysco4FUpU=
-github.com/mattn/go-runewidth v0.0.7/go.mod h1:H031xJmbD/WCDINGzjvQ9THkh0rPKHF+m2gUSrubnMI=
-github.com/mattn/go-tty v0.0.4 h1:NVikla9X8MN0SQAqCYzpGyXv0jY7MNl3HOWD2dkle7E=
-github.com/mattn/go-tty v0.0.4/go.mod h1:u5GGXBtZU6RQoKV8gY5W6UhMudbR5vXnUe7j3pxse28=
 github.com/orisano/pixelmatch v0.0.0-20210112091706-4fa4c7ba91d5 h1:1SoBaSPudixRecmlHXb/GxmaD3fLMtHIDN13QujwQuc=
 github.com/orisano/pixelmatch v0.0.0-20210112091706-4fa4c7ba91d5/go.mod h1:nZgzbfBr3hhjoZnS66nKrHmduYNpc34ny7RK4z5/HM0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
-github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
+github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
+go.bug.st/serial v1.1.3 h1:YEBxJa9pKS9Wdg46B/jiaKbvvbUrjhZZZITfJHEJhaE=
+go.bug.st/serial v1.1.3/go.mod h1:8TT7u/SwwNIpJ8QaG4s+HTjFt9ReXs2cdOU7ZEk50Dk=
 go.bug.st/serial v1.3.5 h1:k50SqGZCnHZ2MiBQgzccXWG+kd/XpOs1jUljpDDKzaE=
 go.bug.st/serial v1.3.5/go.mod h1:z8CesKorE90Qr/oRSJiEuvzYRKol9r/anJZEb5kt304=
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4 h1:6zppjxzCulZykYSLyVDYbneBfbaBIQPYMevg0bEwv2s=
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
-golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20191008105621-543471e840be/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20191120155948-bd437916bb0e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200116001909-b77594299b42/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200909081042-eff7692f9009/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201207223542-d4d67f95c62d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20211124211545-fe61309f8881/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220114195835-da31bd327af9 h1:XfKQ4OlFl8okEOr5UvAqFRVj8pY/4yfcXrddB8qAbU0=
+golang.org/x/sys v0.0.0-20220114195835-da31bd327af9/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220829200755-d48e67d00261 h1:v6hYoSR9T5oet+pMXwUWkbiVqx/63mlHjefrHmxwfeY=
 golang.org/x/sys v0.0.0-20220829200755-d48e67d00261/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/tools v0.1.11 h1:loJ25fNOEhSXfHrpoGj91eCUThwdNX6u24rO1xnNteY=
 golang.org/x/tools v0.1.11/go.mod h1:SgwaegtQh8clINPpECJMqnxLv9I09HLqnW3RMqW0CA4=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
 gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 tinygo.org/x/go-llvm v0.0.0-20220802112859-5bb0b77907a7 h1:nSLR52mUw7DPQQVA3ZJFH63zjU4ME84fKiin6mdnYWc=
 tinygo.org/x/go-llvm v0.0.0-20220802112859-5bb0b77907a7/go.mod h1:GFbusT2VTA4I+l4j80b17KFK+6whv69Wtny5U+T8RR0=
@@ -12,7 +12,7 @@ import (

 // Version of TinyGo.
 // Update this value before release of new version of software.
-const Version = "0.26.0"
+const Version = "0.26.0-dev"

 var (
 	// This variable is set at build time using -ldflags parameters.
@@ -369,11 +369,6 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 				nBytes := uint32(operands[3].Uint())
 				dstObj := mem.getWritable(dst.index())
 				dstBuf := dstObj.buffer.asRawValue(r)
-				if mem.get(src.index()).buffer == nil {
-					// Looks like the source buffer is not defined.
-					// This can happen with //extern or //go:embed.
-					return nil, mem, r.errorAt(inst, errUnsupportedRuntimeInst)
-				}
 				srcBuf := mem.get(src.index()).buffer.asRawValue(r)
 				copy(dstBuf.buf[dst.offset():dst.offset()+nBytes], srcBuf.buf[src.offset():])
 				dstObj.buffer = dstBuf
@@ -440,7 +440,7 @@ func (p *Package) parseFiles() ([]*ast.File, error) {
 		var initialCFlags []string
 		initialCFlags = append(initialCFlags, p.program.config.CFlags()...)
 		initialCFlags = append(initialCFlags, "-I"+p.Dir)
-		generated, headerCode, cflags, ldflags, accessedFiles, errs := cgo.Process(files, p.program.workingDir, p.ImportPath, p.program.fset, initialCFlags, p.program.clangHeaders)
+		generated, headerCode, cflags, ldflags, accessedFiles, errs := cgo.Process(files, p.program.workingDir, p.program.fset, initialCFlags, p.program.clangHeaders)
 		p.CFlags = append(initialCFlags, cflags...)
 		p.CGoHeaders = headerCode
 		for path, hash := range accessedFiles {
@@ -26,7 +26,6 @@ import (
 	"time"

 	"github.com/google/shlex"
-	"github.com/inhies/go-bytesize"
 	"github.com/mattn/go-colorable"
 	"github.com/tinygo-org/tinygo/builder"
 	"github.com/tinygo-org/tinygo/compileopts"
@@ -423,6 +422,7 @@ func Flash(pkgName, port string, options *compileopts.Options) error {
 			if err != nil {
 				return &commandError{"failed to flash", result.Binary, err}
 			}
+			return nil
 		case "msd":
 			switch fileExt {
 			case ".uf2":
@@ -430,11 +430,13 @@ func Flash(pkgName, port string, options *compileopts.Options) error {
 				if err != nil {
 					return &commandError{"failed to flash", result.Binary, err}
 				}
+				return nil
 			case ".hex":
 				err := flashHexUsingMSD(config.Target.FlashVolume, result.Binary, config.Options)
 				if err != nil {
 					return &commandError{"failed to flash", result.Binary, err}
 				}
+				return nil
 			default:
 				return errors.New("mass storage device flashing currently only supports uf2 and hex")
 			}
@@ -455,6 +457,7 @@ func Flash(pkgName, port string, options *compileopts.Options) error {
 			if err != nil {
 				return &commandError{"failed to flash", result.Binary, err}
 			}
+			return nil
 		case "bmp":
 			gdb, err := config.Target.LookupGDB()
 			if err != nil {
@@ -473,13 +476,10 @@ func Flash(pkgName, port string, options *compileopts.Options) error {
 			if err != nil {
 				return &commandError{"failed to flash", result.Binary, err}
 			}
+			return nil
 		default:
 			return fmt.Errorf("unknown flash method: %s", flashMethod)
 		}
-		if options.Monitor {
-			return Monitor("", options)
-		}
-		return nil
 	})
 }

@@ -998,8 +998,7 @@ func getDefaultPort(portFlag string, usbInterfaces []string) (port string, err e
 			preferredPortIDs = append(preferredPortIDs, [2]uint16{uint16(vid), uint16(pid)})
 		}

-		var primaryPorts []string   // ports picked from preferred USB VID/PID
-		var secondaryPorts []string // other ports (as a fallback)
+		var primaryPorts []string // ports picked from preferred USB VID/PID
 		for _, p := range portsList {
 			if !p.IsUSB {
 				continue
@@ -1021,8 +1020,6 @@ func getDefaultPort(portFlag string, usbInterfaces []string) (port string, err e
 					continue
 				}
 			}
-
-			secondaryPorts = append(secondaryPorts, p.Name)
 		}
 		if len(primaryPorts) == 1 {
 			// There is exactly one match in the set of preferred ports. Use
@@ -1034,10 +1031,18 @@ func getDefaultPort(portFlag string, usbInterfaces []string) (port string, err e
 			// one device of the same type are connected (e.g. two Arduino
 			// Unos).
 			ports = primaryPorts
-		} else {
-			// No preferred ports found. Fall back to other serial ports
-			// available in the system.
-			ports = secondaryPorts
+		}
+
+		if 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()
+			}
 		}
 	default:
 		return "", errors.New("unable to search for a default USB device to be flashed on this OS")
@@ -1052,9 +1057,7 @@ func getDefaultPort(portFlag string, usbInterfaces []string) (port string, err e
 	}

 	if len(portCandidates) == 0 {
-		if len(usbInterfaces) > 0 {
-			return "", errors.New("unable to search for a default USB device - use -port flag, available ports are " + strings.Join(ports, ", "))
-		} else if len(ports) == 1 {
+		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, ", "))
@@ -1119,7 +1122,6 @@ func usage(command string) {
 		fmt.Fprintln(os.Stderr, "  flash:   compile and flash to the device")
 		fmt.Fprintln(os.Stderr, "  gdb:     run/flash and immediately enter GDB")
 		fmt.Fprintln(os.Stderr, "  lldb:    run/flash and immediately enter LLDB")
-		fmt.Fprintln(os.Stderr, "  monitor: open communication port")
 		fmt.Fprintln(os.Stderr, "  env:     list environment variables used during build")
 		fmt.Fprintln(os.Stderr, "  list:    run go list using the TinyGo root")
 		fmt.Fprintln(os.Stderr, "  clean:   empty cache directory ("+goenv.Get("GOCACHE")+")")
@@ -1316,12 +1318,6 @@ func main() {
 	var tags buildutil.TagsFlag
 	flag.Var(&tags, "tags", "a space-separated list of extra build tags")
 	target := flag.String("target", "", "chip/board name or JSON target specification file")
-	var stackSize uint64
-	flag.Func("stack-size", "goroutine stack size (if unknown at compile time)", func(s string) error {
-		size, err := bytesize.Parse(s)
-		stackSize = uint64(size)
-		return err
-	})
 	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")
@@ -1336,8 +1332,6 @@ func main() {
 	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")
 	cpuprofile := flag.String("cpuprofile", "", "cpuprofile output")
-	monitor := flag.Bool("monitor", false, "enable serial monitor")
-	baudrate := flag.Int("baudrate", 115200, "baudrate of serial monitor")

 	var flagJSON, flagDeps, flagTest bool
 	if command == "help" || command == "list" || command == "info" || command == "build" {
@@ -1404,7 +1398,6 @@ func main() {
 		GOARCH:          goenv.Get("GOARCH"),
 		GOARM:           goenv.Get("GOARM"),
 		Target:          *target,
-		StackSize:       stackSize,
 		Opt:             *opt,
 		GC:              *gc,
 		PanicStrategy:   *panicStrategy,
@@ -1427,8 +1420,6 @@ func main() {
 		OpenOCDCommands: ocdCommands,
 		LLVMFeatures:    *llvmFeatures,
 		PrintJSON:       flagJSON,
-		Monitor:         *monitor,
-		BaudRate:        *baudrate,
 	}
 	if *printCommands {
 		options.PrintCommands = printCommand
@@ -1619,9 +1610,6 @@ func main() {
 			fmt.Println("FAIL")
 			os.Exit(1)
 		}
-	case "monitor":
-		err := Monitor(*port, options)
-		handleCompilerError(err)
 	case "targets":
 		dir := filepath.Join(goenv.Get("TINYGOROOT"), "targets")
 		entries, err := ioutil.ReadDir(dir)
@@ -1,106 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"os"
-	"os/signal"
-	"time"
-
-	"github.com/mattn/go-tty"
-	"github.com/tinygo-org/tinygo/builder"
-	"github.com/tinygo-org/tinygo/compileopts"
-	"go.bug.st/serial"
-)
-
-// Monitor connects to the given port and reads/writes the serial port.
-func Monitor(port string, options *compileopts.Options) error {
-	config, err := builder.NewConfig(options)
-	if err != nil {
-		return err
-	}
-
-	wait := 300
-	for i := 0; i <= wait; i++ {
-		port, err = getDefaultPort(port, config.Target.SerialPort)
-		if err != nil {
-			if i < wait {
-				time.Sleep(10 * time.Millisecond)
-				continue
-			}
-			return err
-		}
-		break
-	}
-
-	br := options.BaudRate
-	if br <= 0 {
-		br = 115200
-	}
-
-	wait = 300
-	var p serial.Port
-	for i := 0; i <= wait; i++ {
-		p, err = serial.Open(port, &serial.Mode{BaudRate: br})
-		if err != nil {
-			if i < wait {
-				time.Sleep(10 * time.Millisecond)
-				continue
-			}
-			return err
-		}
-		break
-	}
-	defer p.Close()
-
-	tty, err := tty.Open()
-	if err != nil {
-		return err
-	}
-	defer tty.Close()
-
-	sig := make(chan os.Signal, 1)
-	signal.Notify(sig, os.Interrupt)
-	defer signal.Stop(sig)
-
-	go func() {
-		<-sig
-		tty.Close()
-		os.Exit(0)
-	}()
-
-	fmt.Printf("Connected to %s. Press Ctrl-C to exit.\n", port)
-
-	errCh := make(chan error, 1)
-
-	go func() {
-		buf := make([]byte, 100*1024)
-		for {
-			n, err := p.Read(buf)
-			if err != nil {
-				errCh <- fmt.Errorf("read error: %w", err)
-				return
-			}
-
-			if n == 0 {
-				continue
-			}
-			fmt.Printf("%v", string(buf[:n]))
-		}
-	}()
-
-	go func() {
-		for {
-			r, err := tty.ReadRune()
-			if err != nil {
-				errCh <- err
-				return
-			}
-			if r == 0 {
-				continue
-			}
-			p.Write([]byte(string(r)))
-		}
-	}()
-
-	return <-errCh
-}
@@ -1,5 +1,5 @@
-//go:build nrf || stm32 || (sam && atsamd51) || (sam && atsame5x)
-// +build nrf stm32 sam,atsamd51 sam,atsame5x
+//go:build nrf52840 || stm32 || (sam && atsamd51) || (sam && atsame5x) || rp2040
+// +build nrf52840 stm32 sam,atsamd51 sam,atsame5x rp2040

 package rand

@@ -0,0 +1,49 @@
+// Reads multiple rp2040 ADC channels concurrently. Including the internal temperature sensor
+
+package main
+
+import (
+	"fmt"
+	"machine"
+	"time"
+)
+
+type celsius float32
+
+func (c celsius) String() string {
+	return fmt.Sprintf("%4.1f℃", c)
+}
+
+// rp2040 ADC is 12 bits. Reading are shifted <<4 to fill the 16-bit range.
+var adcReading [3]uint16
+
+func readADC(a machine.ADC, w time.Duration, i int) {
+	for {
+		adcReading[i] = a.Get()
+		time.Sleep(w)
+	}
+}
+
+func main() {
+	machine.InitADC()
+	a0 := machine.ADC{machine.ADC0} // GPIO26 input
+	a1 := machine.ADC{machine.ADC1} // GPIO27 input
+	a2 := machine.ADC{machine.ADC2} // GPIO28 input
+	t := machine.ADC_TEMP_SENSOR    // Internal Temperature sensor
+	// Configure sets the GPIOs to PinAnalog mode
+	a0.Configure(machine.ADCConfig{})
+	a1.Configure(machine.ADCConfig{})
+	a2.Configure(machine.ADCConfig{})
+	// Configure powers on the temperature sensor
+	t.Configure(machine.ADCConfig{})
+
+	// Safe to read concurrently
+	go readADC(a0, 10*time.Millisecond, 0)
+	go readADC(a1, 17*time.Millisecond, 1)
+	go readADC(a2, 29*time.Millisecond, 2)
+
+	for {
+		fmt.Printf("ADC0: %5d ADC1: %5d ADC2: %5d Temp: %v\n\r", adcReading[0], adcReading[1], adcReading[2], celsius(float32(t.ReadTemperature())/1000))
+		time.Sleep(1000 * time.Millisecond)
+	}
+}
@@ -1,23 +0,0 @@
-// Read the internal temperature sensor of the chip.
-
-package main
-
-import (
-	"fmt"
-	"machine"
-	"time"
-)
-
-type celsius float32
-
-func (c celsius) String() string {
-	return fmt.Sprintf("%4.1f℃", c)
-}
-
-func main() {
-	for {
-		temp := celsius(float32(machine.ReadTemperature()) / 1000)
-		println("temperature:", temp.String())
-		time.Sleep(time.Second)
-	}
-}
@@ -7,7 +7,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0x07738135
+const RESET_MAGIC_VALUE = 0x07738135

 // GPIO Pins
 const (
@@ -7,7 +7,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0x07738135
+const RESET_MAGIC_VALUE = 0x07738135

 // GPIO Pins
 const (
@@ -7,7 +7,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0x07738135
+const RESET_MAGIC_VALUE = 0x07738135

 // GPIO Pins
 const (
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0x07738135
+const RESET_MAGIC_VALUE = 0x07738135

 // GPIO Pins - Digital Low
 const (
@@ -8,7 +8,7 @@ import (
 )

 // Definition for compatibility, but not used
-const resetMagicValue = 0x00000000
+const RESET_MAGIC_VALUE = 0x00000000

 const (
 	LED    = PC18
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0xf01669ef
+const RESET_MAGIC_VALUE = 0xf01669ef

 // GPIO Pins
 const (
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0xf01669ef
+const RESET_MAGIC_VALUE = 0xf01669ef

 // GPIO Pins
 const (
@@ -8,7 +8,7 @@ import (
 )

 // used to reset into bootloader
-const resetMagicValue = 0xf01669ef
+const RESET_MAGIC_VALUE = 0xf01669ef

 // GPIO Pins
 const (
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0xf01669ef
+const RESET_MAGIC_VALUE = 0xf01669ef

 // GPIO Pins
 const (
@@ -245,7 +245,7 @@ const (

 // Other peripheral constants
 const (
-	resetMagicValue = 0xF01669EF // Used to reset into bootloader
+	RESET_MAGIC_VALUE = 0xF01669EF // Used to reset into bootloader
 )

 // USB CDC pins
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0xf01669ef
+const RESET_MAGIC_VALUE = 0xf01669ef

 // GPIO Pins
 const (
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0xf01669ef
+const RESET_MAGIC_VALUE = 0xf01669ef

 // GPIO Pins
 const (
@@ -52,8 +52,8 @@ const (
 	I2C0_SDA_PIN = GPIO20
 	I2C0_SCL_PIN = GPIO21

-	I2C1_SDA_PIN = NoPin // not pinned out
-	I2C1_SCL_PIN = NoPin // not pinned out
+	I2C1_SDA_PIN = 31 // not pinned out
+	I2C1_SCL_PIN = 31 // not pinned out
 )

 // SPI default pins
@@ -65,9 +65,9 @@ const (
 	// Default Serial In Bus 1 for SPI communications
 	SPI1_SDI_PIN = GPIO28 // Rx

-	SPI0_SCK_PIN = NoPin // not pinned out
-	SPI0_SDO_PIN = NoPin // not pinned out
-	SPI0_SDI_PIN = NoPin // not pinned out
+	SPI0_SCK_PIN = 31 // not pinned out
+	SPI0_SDO_PIN = 31 // not pinned out
+	SPI0_SDI_PIN = 31 // not pinned out
 )

 // UART pins
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0xF01669EF
+const RESET_MAGIC_VALUE = 0xF01669EF

 // Digital pins
 const (
@@ -18,15 +18,15 @@ const (

 // MDBT50Q-RX dongle does not have pins broken out for the peripherals below,
 // however the machine_nrf*.go implementations of I2C/SPI/etc expect the pin
-// constants to be defined, so we are defining them all as NoPin
+// constants to be defined, so we are defining them all as 0
 const (
-	UART_TX_PIN  = NoPin
-	UART_RX_PIN  = NoPin
-	SDA_PIN      = NoPin
-	SCL_PIN      = NoPin
-	SPI0_SCK_PIN = NoPin
-	SPI0_SDO_PIN = NoPin
-	SPI0_SDI_PIN = NoPin
+	UART_TX_PIN  = 0
+	UART_RX_PIN  = 0
+	SDA_PIN      = 0
+	SCL_PIN      = 0
+	SPI0_SCK_PIN = 0
+	SPI0_SDO_PIN = 0
+	SPI0_SDI_PIN = 0
 )

 // USB CDC identifiers
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0xf01669ef
+const RESET_MAGIC_VALUE = 0xf01669ef

 // GPIO Pins
 const (
@@ -7,7 +7,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0x07738135
+const RESET_MAGIC_VALUE = 0x07738135

 // Note: On the P1AM-100, pins D8, D9, D10, A3, and A4 are used for
 // communication with the base controller.
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0xf01669ef
+const RESET_MAGIC_VALUE = 0xf01669ef

 // GPIO Pins
 const (
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0xf01669ef
+const RESET_MAGIC_VALUE = 0xf01669ef

 // GPIO Pins
 const (
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0xf01669ef
+const RESET_MAGIC_VALUE = 0xf01669ef

 // GPIO Pins
 const (
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0xf01669ef
+const RESET_MAGIC_VALUE = 0xf01669ef

 // GPIO Pins
 const (
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0xf01669ef
+const RESET_MAGIC_VALUE = 0xf01669ef

 // GPIO Pins
 const (
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0xf01669ef
+const RESET_MAGIC_VALUE = 0xf01669ef

 const (
 	ADC0 = A0
@@ -104,7 +104,7 @@ const (

 var (
 	usb_VID uint16 = 0x2886
-	usb_PID uint16 = 0x8045
+	usb_PID uint16 = 0x0045
 )

 var (
@@ -4,7 +4,7 @@
 package machine

 // used to reset into bootloader
-const resetMagicValue = 0xf01669ef
+const RESET_MAGIC_VALUE = 0xf01669ef

 // GPIO Pins
 const (
@@ -8,8 +8,6 @@ import (
 )

 // TWI_FREQ is the I2C bus speed. Normally either 100 kHz, or 400 kHz for high-speed bus.
-//
-// Deprecated: use 100 * machine.KHz or 400 * machine.KHz instead.
 const (
 	TWI_FREQ_100KHZ = 100000
 	TWI_FREQ_400KHZ = 400000
@@ -18,13 +18,6 @@ var (
 // particular chip but instead runs in WebAssembly for example.
 const Device = deviceName

-// Generic constants.
-const (
-	KHz = 1000
-	MHz = 1000_000
-	GHz = 1000_000_000
-)
-
 // 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.
@@ -26,7 +26,7 @@ type I2CConfig struct {
 func (i2c *I2C) Configure(config I2CConfig) error {
 	// Default I2C bus speed is 100 kHz.
 	if config.Frequency == 0 {
-		config.Frequency = 100 * KHz
+		config.Frequency = TWI_FREQ_100KHZ
 	}

 	// Activate internal pullups for twi.
@@ -10,6 +10,7 @@ package machine
 import (
 	"device/arm"
 	"device/sam"
+	"errors"
 	"runtime/interrupt"
 	"unsafe"
 )
@@ -676,7 +677,7 @@ const i2cTimeout = 1000
 func (i2c *I2C) Configure(config I2CConfig) error {
 	// Default I2C bus speed is 100 kHz.
 	if config.Frequency == 0 {
-		config.Frequency = 100 * KHz
+		config.Frequency = TWI_FREQ_100KHZ
 	}
 	if config.SDA == 0 && config.SCL == 0 {
 		config.SDA = SDA_PIN
@@ -1273,6 +1274,10 @@ func (spi SPI) Transfer(w byte) (byte, error) {
 	return byte(spi.Bus.DATA.Get()), nil
 }

+var (
+	ErrTxInvalidSliceSize = errors.New("SPI write and read slices must be same size")
+)
+
 // Tx handles read/write operation for SPI interface. Since SPI is a syncronous write/read
 // interface, there must always be the same number of bytes written as bytes read.
 // The Tx method knows about this, and offers a few different ways of calling it.
@@ -1735,7 +1740,7 @@ func EnterBootloader() {

 	// Perform magic reset into bootloader, as mentioned in
 	// https://github.com/arduino/ArduinoCore-samd/issues/197
-	*(*uint32)(unsafe.Pointer(uintptr(0x20007FFC))) = resetMagicValue
+	*(*uint32)(unsafe.Pointer(uintptr(0x20007FFC))) = RESET_MAGIC_VALUE

 	arm.SystemReset()
 }
@@ -10,6 +10,7 @@ package machine
 import (
 	"device/arm"
 	"device/sam"
+	"errors"
 	"runtime/interrupt"
 	"unsafe"
 )
@@ -1150,7 +1151,7 @@ const i2cTimeout = 1000
 func (i2c *I2C) Configure(config I2CConfig) error {
 	// Default I2C bus speed is 100 kHz.
 	if config.Frequency == 0 {
-		config.Frequency = 100 * KHz
+		config.Frequency = TWI_FREQ_100KHZ
 	}

 	// Use default I2C pins if not set.
@@ -1526,6 +1527,10 @@ func (spi SPI) Transfer(w byte) (byte, error) {
 	return byte(spi.Bus.DATA.Get()), nil
 }

+var (
+	ErrTxInvalidSliceSize = errors.New("SPI write and read slices must be same size")
+)
+
 // Tx handles read/write operation for SPI interface. Since SPI is a syncronous write/read
 // interface, there must always be the same number of bytes written as bytes read.
 // The Tx method knows about this, and offers a few different ways of calling it.
@@ -1975,7 +1980,7 @@ func EnterBootloader() {

 	// Perform magic reset into bootloader, as mentioned in
 	// https://github.com/arduino/ArduinoCore-samd/issues/197
-	*(*uint32)(unsafe.Pointer(uintptr(0x20000000 + HSRAM_SIZE - 4))) = resetMagicValue
+	*(*uint32)(unsafe.Pointer(uintptr(0x20000000 + HSRAM_SIZE - 4))) = RESET_MAGIC_VALUE

 	arm.SystemReset()
 }
@@ -59,9 +59,12 @@ type PinChange uint8

 // Pin change interrupt constants for SetInterrupt.
 const (
-	PinRising PinChange = iota + 1
+	PinNoInterrupt PinChange = iota
+	PinRising
 	PinFalling
 	PinToggle
+	PinLowLevel
+	PinHighLevel
 )

 // Configure this pin with the given configuration.
@@ -187,7 +190,7 @@ func (p Pin) SetInterrupt(change PinChange, callback func(Pin)) (err error) {
 		return ErrInvalidInputPin
 	}

-	if callback == nil {
+	if callback == nil || change == PinNoInterrupt {
 		// Disable this pin interrupt
 		p.pin().ClearBits(esp.GPIO_PIN_PIN_INT_TYPE_Msk | esp.GPIO_PIN_PIN_INT_ENA_Msk)

@@ -261,6 +264,15 @@ type UART struct {
 	DataOverflowDetected bool // set when data overflow detected in UART FIFO buffer or RingBuffer
 }

+type UARTStopBits int
+
+const (
+	UARTStopBits_Default UARTStopBits = iota
+	UARTStopBits_1
+	UARTStopBits_1_5
+	UARTStopBits_2
+)
+
 const (
 	defaultDataBits = 8
 	defaultStopBit  = 1
@@ -231,7 +231,7 @@ type I2CConfig struct {
 func (i2c *I2C) Configure(config I2CConfig) error {
 	var i2cClockFrequency uint32 = 32000000
 	if config.Frequency == 0 {
-		config.Frequency = 100 * KHz
+		config.Frequency = TWI_FREQ_100KHZ
 	}

 	if config.SDA == 0 && config.SCL == 0 {
@@ -23,17 +23,11 @@ type PinChange uint8
 // Pin modes.
 const (
 	PinInput PinMode = iota
-	PinInputPullup
-	PinInputPulldown
+	PinInputPullUp
+	PinInputPullDown
 	PinOutput
 )

-// Deprecated: use PinInputPullup and PinInputPulldown instead.
-const (
-	PinInputPullUp   = PinInputPullup
-	PinInputPullDown = PinInputPulldown
-)
-
 // FPIOA internal pull resistors.
 const (
 	fpioaPullNone fpioaPullMode = iota
@@ -95,10 +89,10 @@ func (p Pin) Configure(config PinConfig) {
 	case PinInput:
 		p.setFPIOAIOPull(fpioaPullNone)
 		input = true
-	case PinInputPullup:
+	case PinInputPullUp:
 		p.setFPIOAIOPull(fpioaPullUp)
 		input = true
-	case PinInputPulldown:
+	case PinInputPullDown:
 		p.setFPIOAIOPull(fpioaPullDown)
 		input = true
 	case PinOutput:
@@ -523,7 +517,7 @@ type I2CConfig struct {
 func (i2c *I2C) Configure(config I2CConfig) error {

 	if config.Frequency == 0 {
-		config.Frequency = 100 * KHz
+		config.Frequency = TWI_FREQ_100KHZ
 	}

 	if config.SDA == 0 && config.SCL == 0 {
@@ -21,8 +21,8 @@ func CPUFrequency() uint32 {
 const (
 	// GPIO
 	PinInput PinMode = iota
-	PinInputPullup
-	PinInputPulldown
+	PinInputPullUp
+	PinInputPullDown
 	PinOutput
 	PinOutputOpenDrain
 	PinDisable
@@ -45,16 +45,12 @@ const (
 	PinModeI2CSCL
 )

-// Deprecated: use PinInputPullup and PinInputPulldown instead.
-const (
-	PinInputPullUp   = PinInputPullup
-	PinInputPullDown = PinInputPulldown
-)
-
 type PinChange uint8

 const (
-	PinRising PinChange = iota + 2
+	PinLow PinChange = iota
+	PinHigh
+	PinRising
 	PinFalling
 	PinToggle
 )
@@ -263,11 +259,11 @@ func (p Pin) Configure(config PinConfig) {
 		gpio.GDIR.ClearBits(p.getMask())
 		pad.Set(dse(7))

-	case PinInputPullup:
+	case PinInputPullUp:
 		gpio.GDIR.ClearBits(p.getMask())
 		pad.Set(dse(7) | pke | pue | pup(3) | hys)

-	case PinInputPulldown:
+	case PinInputPullDown:
 		gpio.GDIR.ClearBits(p.getMask())
 		pad.Set(dse(7) | pke | pue | hys)

@@ -391,7 +387,7 @@ func (p Pin) SetInterrupt(change PinChange, callback func(Pin)) error {
 	mask := p.getMask()
 	if nil != callback {
 		switch change {
-		case PinRising, PinFalling:
+		case PinLow, PinHigh, PinRising, PinFalling:
 			gpio.EDGE_SEL.ClearBits(mask)
 			var reg *volatile.Register32
 			var pos uint8
@@ -750,7 +746,7 @@ func (p Pin) getMuxMode(config PinConfig) uint32 {
 	switch config.Mode {

 	// GPIO
-	case PinInput, PinInputPullup, PinInputPulldown,
+	case PinInput, PinInputPullUp, PinInputPullDown,
 		PinOutput, PinOutputOpenDrain, PinDisable:
 		mode := uint32(0x5) // GPIO is always alternate function 5
 		if forcePath {
@@ -10,6 +10,15 @@ import (
 	"errors"
 )

+const (
+	TWI_FREQ_BUS     = 24000000        // LPI2C root clock is on 24 MHz OSC
+	TWI_FREQ_100KHZ  = 100000          // StandardMode (100 kHz)
+	TWI_FREQ_400KHZ  = 400000          // FastMode (400 kHz)
+	TWI_FREQ_1MHZ    = 1000000         // FastModePlus (1 MHz)
+	TWI_FREQ_5MHZ    = 5000000         // UltraFastMode (5 MHz)
+	TWI_FREQ_DEFAULT = TWI_FREQ_100KHZ // default to StandardMode (100 kHz)
+)
+
 var (
 	errI2CWriteTimeout       = errors.New("I2C timeout during write")
 	errI2CReadTimeout        = errors.New("I2C timeout during read")
@@ -165,7 +174,7 @@ func (i2c *I2C) Configure(config I2CConfig) {

 	freq := config.Frequency
 	if 0 == freq {
-		freq = 100 * KHz
+		freq = TWI_FREQ_DEFAULT
 	}

 	// reset clock and registers, and enable LPI2C module interface
@@ -296,7 +305,7 @@ func (i2c *I2C) setFrequency(freq uint32) {
 	wasEnabled := i2c.Bus.MCR.HasBits(nxp.LPI2C_MCR_MEN)
 	i2c.Bus.MCR.ClearBits(nxp.LPI2C_MCR_MEN)

-	// baud rate = (24MHz/(2^pre))/(CLKLO+1 + CLKHI+1 + FLOOR((2+FILTSCL)/(2^pre)))
+	// baud rate = (TWI_FREQ_BUS/(2^pre))/(CLKLO+1 + CLKHI+1 + FLOOR((2+FILTSCL)/(2^pre)))
 	// assume: CLKLO=2*CLKHI, SETHOLD=CLKHI, DATAVD=CLKHI/2
 	for pre := uint32(1); pre <= 128; pre *= 2 {
 		if bestError == 0 {
@@ -305,9 +314,9 @@ func (i2c *I2C) setFrequency(freq uint32) {
 		for clkHi := uint32(1); clkHi < 32; clkHi++ {
 			var absError, rate uint32
 			if clkHi == 1 {
-				rate = (24 * MHz / pre) / (1 + 3 + 2 + 2/pre)
+				rate = (TWI_FREQ_BUS / pre) / (1 + 3 + 2 + 2/pre)
 			} else {
-				rate = (24 * MHz / pre) / (3*clkHi + 2 + 2/pre)
+				rate = (TWI_FREQ_BUS / pre) / (3*clkHi + 2 + 2/pre)
 			}
 			if freq > rate {
 				absError = freq - rate
@@ -361,15 +370,15 @@ func (i2c *I2C) setFrequency(freq uint32) {
 		mcfgr2, mcfgr3 uint32
 	)
 	const i2cClockStretchTimeout = 15000 // microseconds
-	if freq >= 5*MHz {
+	if freq >= TWI_FREQ_5MHZ {
 		// I2C UltraFastMode 5 MHz
 		mcfgr2 = 0 // disable glitch filters and timeout for UltraFastMode
 		mcfgr3 = 0 //
-	} else if freq >= 1*MHz {
+	} else if freq >= TWI_FREQ_1MHZ {
 		// I2C FastModePlus 1 MHz
 		mcfgr2 = filtsda(1) | filtscl(1) | busidle(2400) // 100us timeout
 		mcfgr3 = pinlow(i2cClockStretchTimeout*24/256 + 1)
-	} else if freq >= 400*KHz {
+	} else if freq >= TWI_FREQ_400KHZ {
 		// I2C FastMode 400 kHz
 		mcfgr2 = filtsda(2) | filtscl(2) | busidle(3600) // 150us timeout
 		mcfgr3 = pinlow(i2cClockStretchTimeout*24/256 + 1)
@@ -159,8 +159,8 @@ func (uart *UART) Disable() {
 		uart.Bus.CTRL.ClearBits(nxp.LPUART_CTRL_TE | nxp.LPUART_CTRL_RE)

 		// put pins back into GPIO mode
-		uart.rx.Configure(PinConfig{Mode: PinInputPullup})
-		uart.tx.Configure(PinConfig{Mode: PinInputPullup})
+		uart.rx.Configure(PinConfig{Mode: PinInputPullUp})
+		uart.tx.Configure(PinConfig{Mode: PinInputPullUp})
 	}
 	uart.configured = false
 }
@@ -5,10 +5,15 @@ package machine

 import (
 	"device/nrf"
+	"errors"
 	"runtime/interrupt"
 	"unsafe"
 )

+var (
+	ErrTxInvalidSliceSize = errors.New("SPI write and read slices must be same size")
+)
+
 const deviceName = nrf.Device

 const (
@@ -225,7 +230,7 @@ func (i2c *I2C) Configure(config I2CConfig) error {

 	// Default I2C bus speed is 100 kHz.
 	if config.Frequency == 0 {
-		config.Frequency = 100 * KHz
+		config.Frequency = TWI_FREQ_100KHZ
 	}
 	// Default I2C pins if not set.
 	if config.SDA == 0 && config.SCL == 0 {
@@ -248,7 +253,7 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 		(nrf.GPIO_PIN_CNF_DRIVE_S0D1 << nrf.GPIO_PIN_CNF_DRIVE_Pos) |
 		(nrf.GPIO_PIN_CNF_SENSE_Disabled << nrf.GPIO_PIN_CNF_SENSE_Pos))

-	if config.Frequency >= 400*KHz {
+	if config.Frequency == TWI_FREQ_400KHZ {
 		i2c.Bus.FREQUENCY.Set(nrf.TWI_FREQUENCY_FREQUENCY_K400)
 	} else {
 		i2c.Bus.FREQUENCY.Set(nrf.TWI_FREQUENCY_FREQUENCY_K100)
@@ -345,41 +350,3 @@ func (i2c *I2C) readByte() (byte, error) {
 	i2c.Bus.EVENTS_RXDREADY.Set(0)
 	return byte(i2c.Bus.RXD.Get()), nil
 }
-
-var rngStarted = false
-
-// GetRNG returns 32 bits of non-deterministic random data based on internal thermal noise.
-// According to Nordic's documentation, the random output is suitable for cryptographic purposes.
-func GetRNG() (ret uint32, err error) {
-	// There's no apparent way to check the status of the RNG peripheral's task, so simply start it
-	// to avoid deadlocking while waiting for output.
-	if !rngStarted {
-		nrf.RNG.TASKS_START.Set(1)
-		nrf.RNG.SetCONFIG_DERCEN(nrf.RNG_CONFIG_DERCEN_Enabled)
-		rngStarted = true
-	}
-
-	// The RNG returns one byte at a time, so stack up four bytes into a single uint32 for return.
-	for i := 0; i < 4; i++ {
-		// Wait for data to be ready.
-		for nrf.RNG.EVENTS_VALRDY.Get() == 0 {
-		}
-		// Append random byte to output.
-		ret = (ret << 8) ^ nrf.RNG.GetVALUE()
-		// Unset the EVENTS_VALRDY register to avoid reading the same random output twice.
-		nrf.RNG.EVENTS_VALRDY.Set(0)
-	}
-
-	return ret, nil
-}
-
-// ReadTemperature reads the silicon die temperature of the chip. The return
-// value is in milli-celsius.
-func ReadTemperature() int32 {
-	nrf.TEMP.TASKS_START.Set(1)
-	for nrf.TEMP.EVENTS_DATARDY.Get() == 0 {
-	}
-	temp := int32(nrf.TEMP.TEMP.Get()) * 250 // the returned value is in units of 0.25°C
-	nrf.TEMP.EVENTS_DATARDY.Set(0)
-	return temp
-}
@@ -9,16 +9,16 @@ import (
 )

 const (
-	dfuMagicSerialOnlyReset = 0x4e
-	dfuMagicUF2Reset        = 0x57
-	dfuMagicOTAReset        = 0xA8
+	DFU_MAGIC_SERIAL_ONLY_RESET = 0x4e
+	DFU_MAGIC_UF2_RESET         = 0x57
+	DFU_MAGIC_OTA_RESET         = 0xA8
 )

 // EnterSerialBootloader resets the chip into the serial bootloader. After
 // reset, it can be flashed using serial/nrfutil.
 func EnterSerialBootloader() {
 	arm.DisableInterrupts()
-	nrf.POWER.GPREGRET.Set(dfuMagicSerialOnlyReset)
+	nrf.POWER.GPREGRET.Set(DFU_MAGIC_SERIAL_ONLY_RESET)
 	arm.SystemReset()
 }

@@ -26,7 +26,7 @@ func EnterSerialBootloader() {
 // can be flashed via nrfutil or by copying a UF2 file to the mass storage device
 func EnterUF2Bootloader() {
 	arm.DisableInterrupts()
-	nrf.POWER.GPREGRET.Set(dfuMagicUF2Reset)
+	nrf.POWER.GPREGRET.Set(DFU_MAGIC_UF2_RESET)
 	arm.SystemReset()
 }

@@ -34,6 +34,6 @@ func EnterUF2Bootloader() {
 // flashed via an OTA update
 func EnterOTABootloader() {
 	arm.DisableInterrupts()
-	nrf.POWER.GPREGRET.Set(dfuMagicOTAReset)
+	nrf.POWER.GPREGRET.Set(DFU_MAGIC_OTA_RESET)
 	arm.SystemReset()
 }
@@ -0,0 +1,60 @@
+//go:build nrf52840
+// +build nrf52840
+
+package machine
+
+import (
+	"device/nrf"
+)
+
+// Implementation based on Nordic Semiconductor's nRF52840 documentation version 1.7 found here:
+// https://infocenter.nordicsemi.com/pdf/nRF52840_PS_v1.7.pdf
+
+// SetRNGBiasCorrection configures the RNG peripheral's bias correction mechanism. Note that when
+// bias correction is enabled, the peripheral is slower to produce random values.
+func SetRNGBiasCorrection(enabled bool) {
+	var val uint32
+	if enabled {
+		val = nrf.RNG_CONFIG_DERCEN_Enabled
+	}
+	nrf.RNG.SetCONFIG_DERCEN(val)
+}
+
+// RNGBiasCorrectionEnabled determines whether the RNG peripheral's bias correction mechanism is
+// enabled or not.
+func RNGBiasCorrectionEnabled() bool {
+	return nrf.RNG.GetCONFIG_DERCEN() == nrf.RNG_CONFIG_DERCEN_Enabled
+}
+
+// StartRNG starts the RNG peripheral core. This is automatically called by GetRNG, but can be
+// manually called for interacting with the RNG peripheral directly.
+func StartRNG() {
+	nrf.RNG.SetTASKS_START(nrf.RNG_TASKS_START_TASKS_START_Trigger)
+}
+
+// StopRNG stops the RNG peripheral core. This is not called automatically. It may make sense to
+// manually disable RNG peripheral for power conservation.
+func StopRNG() {
+	nrf.RNG.SetTASKS_STOP(nrf.RNG_TASKS_STOP_TASKS_STOP_Trigger)
+}
+
+// GetRNG returns 32 bits of non-deterministic random data based on internal thermal noise.
+// According to Nordic's documentation, the random output is suitable for cryptographic purposes.
+func GetRNG() (ret uint32, err error) {
+	// There's no apparent way to check the status of the RNG peripheral's task, so simply start it
+	// to avoid deadlocking while waiting for output.
+	StartRNG()
+
+	// The RNG returns one byte at a time, so stack up four bytes into a single uint32 for return.
+	for i := 0; i < 4; i++ {
+		// Wait for data to be ready.
+		for nrf.RNG.GetEVENTS_VALRDY() == nrf.RNG_EVENTS_VALRDY_EVENTS_VALRDY_NotGenerated {
+		}
+		// Append random byte to output.
+		ret = (ret << 8) ^ nrf.RNG.GetVALUE()
+		// Unset the EVENTS_VALRDY register to avoid reading the same random output twice.
+		nrf.RNG.SetEVENTS_VALRDY(nrf.RNG_EVENTS_VALRDY_EVENTS_VALRDY_NotGenerated)
+	}
+
+	return ret, nil
+}
@@ -42,19 +42,13 @@ const deviceName = nxp.Device

 const (
 	PinInput PinMode = iota
-	PinInputPullup
-	PinInputPulldown
+	PinInputPullUp
+	PinInputPullDown
 	PinOutput
 	PinOutputOpenDrain
 	PinDisable
 )

-// Deprecated: use PinInputPullup and PinInputPulldown instead.
-const (
-	PinInputPullUp   = PinInputPullup
-	PinInputPullDown = PinInputPulldown
-)
-
 const (
 	PA00 Pin = iota
 	PA01
@@ -229,11 +223,11 @@ func (p Pin) Configure(config PinConfig) {
 		gpio.PDDR.ClearBits(1 << pos)
 		pcr.Set((1 << nxp.PORT_PCR0_MUX_Pos))

-	case PinInputPullup:
+	case PinInputPullUp:
 		gpio.PDDR.ClearBits(1 << pos)
 		pcr.Set((1 << nxp.PORT_PCR0_MUX_Pos) | nxp.PORT_PCR0_PE | nxp.PORT_PCR0_PS)

-	case PinInputPulldown:
+	case PinInputPullDown:
 		gpio.PDDR.ClearBits(1 << pos)
 		pcr.Set((1 << nxp.PORT_PCR0_MUX_Pos) | nxp.PORT_PCR0_PE)

@@ -203,8 +203,8 @@ func (u *UART) Disable() {
 	u.C2.Set(0)

 	// reconfigure pin
-	u.DefaultRX.Configure(PinConfig{Mode: PinInputPullup})
-	u.DefaultTX.Configure(PinConfig{Mode: PinInputPullup})
+	u.DefaultRX.Configure(PinConfig{Mode: PinInputPullUp})
+	u.DefaultTX.Configure(PinConfig{Mode: PinInputPullUp})

 	// clear flags
 	u.S1.Get()
@@ -17,8 +17,8 @@ const (
 	adc0_CH ADCChannel = iota
 	adc1_CH
 	adc2_CH
-	adc3_CH       // Note: GPIO29 not broken out on pico board
-	adcTempSensor // Internal temperature sensor channel
+	adc3_CH         // Note: GPIO29 not broken out on pico board
+	ADC_TEMP_SENSOR // Internal temperature sensor channel
 )

 // Used to serialise ADC sampling
@@ -75,17 +75,19 @@ func (a ADC) GetADCChannel() (c ADCChannel, err error) {
 	return c, err
 }

-// Configure sets the channel's associated pin to analog input mode.
+// Configure sets the channel's associated pin to analog input mode or powers on the temperature sensor for ADC_TEMP_SENSOR.
 // The powered on temperature sensor increases ADC_AVDD current by approximately 40 μA.
 func (c ADCChannel) Configure(config ADCConfig) error {
 	if config.Reference != 0 {
 		adcAref = config.Reference
 	}
-	p, err := c.Pin()
-	if err != nil {
-		return err
+	if p, err := c.Pin(); err == nil {
+		p.Configure(PinConfig{Mode: PinAnalog})
+	}
+	if c == ADC_TEMP_SENSOR {
+		// Enable temperature sensor bias source
+		rp.ADC.CS.SetBits(rp.ADC_CS_TS_EN)
 	}
-	p.Configure(PinConfig{Mode: PinAnalog})
 	return nil
 }

@@ -110,16 +112,13 @@ func (c ADCChannel) getVoltage() uint32 {
 }

 // ReadTemperature does a one-shot sample of the internal temperature sensor and returns a milli-celsius reading.
-func ReadTemperature() (millicelsius int32) {
-	if rp.ADC.CS.Get()&rp.ADC_CS_EN == 0 {
-		InitADC()
+// Only works on the ADC_TEMP_SENSOR channel. aka AINSEL=4. Other channels will return 0
+func (c ADCChannel) ReadTemperature() (millicelsius uint32) {
+	if c != ADC_TEMP_SENSOR {
+		return
 	}
-
-	// Enable temperature sensor bias source
-	rp.ADC.CS.SetBits(rp.ADC_CS_TS_EN)
-
 	// T = 27 - (ADC_voltage - 0.706)/0.001721
-	return (27000<<16 - (int32(adcTempSensor.getVoltage())-706<<16)*581) >> 16
+	return (27000<<16 - (c.getVoltage()-706<<16)*581) >> 16
 }

 // waitForReady spins waiting for the ADC peripheral to become ready.
@@ -10,6 +10,11 @@ import (
 	"unsafe"
 )

+const (
+	KHz = 1000
+	MHz = 1000000
+)
+
 func CPUFrequency() uint32 {
 	return 125 * MHz
 }
@@ -226,8 +226,12 @@ type PinChange uint8

 // Pin change interrupt constants for SetInterrupt.
 const (
+	// PinLevelLow triggers whenever pin is at a low (around 0V) logic level.
+	PinLevelLow PinChange = 1 << iota
+	// PinLevelLow triggers whenever pin is at a high (around 3V) logic level.
+	PinLevelHigh
 	// Edge falling
-	PinFalling PinChange = 4 << iota
+	PinFalling
 	// Edge rising
 	PinRising
 )
@@ -13,10 +13,6 @@ import (
 const numberOfCycles = 32

 // GetRNG returns 32 bits of semi-random data based on ring oscillator.
-//
-// Unlike some other implementations of GetRNG, these random numbers are not
-// cryptographically secure and must not be used for cryptographic operations
-// (nonces, etc).
 func GetRNG() (uint32, error) {
 	var val uint32
 	for i := 0; i < 4; i++ {
@@ -38,9 +38,10 @@ type SPIConfig struct {
 }

 var (
-	ErrLSBNotSupported = errors.New("SPI LSB unsupported on PL022")
-	ErrSPITimeout      = errors.New("SPI timeout")
-	ErrSPIBaud         = errors.New("SPI baud too low or above 66.5Mhz")
+	ErrLSBNotSupported    = errors.New("SPI LSB unsupported on PL022")
+	ErrTxInvalidSliceSize = errors.New("SPI write and read slices must be same size")
+	ErrSPITimeout         = errors.New("SPI timeout")
+	ErrSPIBaud            = errors.New("SPI baud too low or above 66.5Mhz")
 )

 type SPI struct {
@@ -137,7 +137,7 @@ func (i2c *I2C) Configure(config I2CConfig) error {

 	// default to 100 kHz (Sm, standard mode) if no frequency is set
 	if config.Frequency == 0 {
-		config.Frequency = 100 * KHz
+		config.Frequency = TWI_FREQ_100KHZ
 	}

 	// configure I2C input clock
@@ -1,5 +1,5 @@
-//go:build !baremetal || atmega || esp32 || fe310 || k210 || nrf || (nxp && !mk66f18) || rp2040 || sam || (stm32 && !stm32f7x2 && !stm32l5x2)
-// +build !baremetal atmega esp32 fe310 k210 nrf nxp,!mk66f18 rp2040 sam stm32,!stm32f7x2,!stm32l5x2
+//go:build !baremetal || (stm32 && !stm32f7x2 && !stm32l5x2) || fe310 || k210 || (nxp && !mk66f18) || atmega
+// +build !baremetal stm32,!stm32f7x2,!stm32l5x2 fe310 k210 nxp,!mk66f18 atmega

 package machine

@@ -17,3 +17,58 @@ var (
 	ErrTxInvalidSliceSize      = errors.New("SPI write and read slices must be same size")
 	errSPIInvalidMachineConfig = errors.New("SPI port was not configured properly by the machine")
 )
+
+// Tx handles read/write operation for SPI interface. Since SPI is a syncronous write/read
+// interface, there must always be the same number of bytes written as bytes read.
+// The Tx method knows about this, and offers a few different ways of calling it.
+//
+// This form sends the bytes in tx buffer, putting the resulting bytes read into the rx buffer.
+// Note that the tx and rx buffers must be the same size:
+//
+//	spi.Tx(tx, rx)
+//
+// This form sends the tx buffer, ignoring the result. Useful for sending "commands" that return zeros
+// until all the bytes in the command packet have been received:
+//
+//	spi.Tx(tx, nil)
+//
+// This form sends zeros, putting the result into the rx buffer. Good for reading a "result packet":
+//
+//	spi.Tx(nil, rx)
+func (spi SPI) Tx(w, r []byte) error {
+	var err error
+
+	switch {
+	case w == nil:
+		// read only, so write zero and read a result.
+		for i := range r {
+			r[i], err = spi.Transfer(0)
+			if err != nil {
+				return err
+			}
+		}
+	case r == nil:
+		// write only
+		for _, b := range w {
+			_, err = spi.Transfer(b)
+			if err != nil {
+				return err
+			}
+		}
+
+	default:
+		// write/read
+		if len(w) != len(r) {
+			return ErrTxInvalidSliceSize
+		}
+
+		for i, b := range w {
+			r[i], err = spi.Transfer(b)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
@@ -1,62 +0,0 @@
-//go:build !baremetal || atmega || fe310 || k210 || (nxp && !mk66f18) || (stm32 && !stm32f7x2 && !stm32l5x2)
-// +build !baremetal atmega fe310 k210 nxp,!mk66f18 stm32,!stm32f7x2,!stm32l5x2
-
-// This file implements the SPI Tx function for targets that don't have a custom
-// (faster) implementation for it.
-
-package machine
-
-// Tx handles read/write operation for SPI interface. Since SPI is a syncronous write/read
-// interface, there must always be the same number of bytes written as bytes read.
-// The Tx method knows about this, and offers a few different ways of calling it.
-//
-// This form sends the bytes in tx buffer, putting the resulting bytes read into the rx buffer.
-// Note that the tx and rx buffers must be the same size:
-//
-//	spi.Tx(tx, rx)
-//
-// This form sends the tx buffer, ignoring the result. Useful for sending "commands" that return zeros
-// until all the bytes in the command packet have been received:
-//
-//	spi.Tx(tx, nil)
-//
-// This form sends zeros, putting the result into the rx buffer. Good for reading a "result packet":
-//
-//	spi.Tx(nil, rx)
-func (spi SPI) Tx(w, r []byte) error {
-	var err error
-
-	switch {
-	case w == nil:
-		// read only, so write zero and read a result.
-		for i := range r {
-			r[i], err = spi.Transfer(0)
-			if err != nil {
-				return err
-			}
-		}
-	case r == nil:
-		// write only
-		for _, b := range w {
-			_, err = spi.Transfer(b)
-			if err != nil {
-				return err
-			}
-		}
-
-	default:
-		// write/read
-		if len(w) != len(r) {
-			return ErrTxInvalidSliceSize
-		}
-
-		for i, b := range w {
-			r[i], err = spi.Transfer(b)
-			if err != nil {
-				return err
-			}
-		}
-	}
-
-	return nil
-}
@@ -8,20 +8,20 @@ import "errors"
 var errUARTBufferEmpty = errors.New("UART buffer empty")

 // UARTParity is the parity setting to be used for UART communication.
-type UARTParity uint8
+type UARTParity int

 const (
 	// ParityNone means to not use any parity checking. This is
 	// the most common setting.
-	ParityNone UARTParity = iota
+	ParityNone UARTParity = 0

 	// ParityEven means to expect that the total number of 1 bits sent
 	// should be an even number.
-	ParityEven
+	ParityEven UARTParity = 1

 	// ParityOdd means to expect that the total number of 1 bits sent
 	// should be an odd number.
-	ParityOdd
+	ParityOdd UARTParity = 2
 )

 // To implement the UART interface for a board, you must declare a concrete type as follows:
@@ -20,46 +20,21 @@ var heapStartSymbol [0]byte
 //go:extern __global_base
 var globalsStartSymbol [0]byte

-const (
-	// wasmMemoryIndex is always zero until the multi-memory feature is used.
-	//
-	// See https://github.com/WebAssembly/multi-memory
-	wasmMemoryIndex = 0
-
-	// wasmPageSize is the size of a page in WebAssembly's 32-bit memory. This
-	// is also its only unit of change.
-	//
-	// See https://www.w3.org/TR/wasm-core-1/#page-size
-	wasmPageSize = 64 * 1024
-)
-
-// wasm_memory_size invokes the "memory.size" instruction, which returns the
-// current size to the memory at the given index (always wasmMemoryIndex), in
-// pages.
-//
 //export llvm.wasm.memory.size.i32
 func wasm_memory_size(index int32) int32

-// wasm_memory_grow invokes the "memory.grow" instruction, which attempts to
-// increase the size of the memory at the given index (always wasmMemoryIndex),
-// by the delta (in pages). This returns the previous size on success of -1 on
-// failure.
-//
 //export llvm.wasm.memory.grow.i32
 func wasm_memory_grow(index int32, delta int32) int32

 var (
-	// heapStart is the current memory offset which starts the heap. The heap
-	// extends from this offset until heapEnd (exclusive).
-	heapStart = uintptr(unsafe.Pointer(&heapStartSymbol))
-
-	// heapEnd is the current memory length in bytes.
-	heapEnd = uintptr(wasm_memory_size(wasmMemoryIndex) * wasmPageSize)
-
+	heapStart    = uintptr(unsafe.Pointer(&heapStartSymbol))
+	heapEnd      = uintptr(wasm_memory_size(0) * wasmPageSize)
 	globalsStart = uintptr(unsafe.Pointer(&globalsStartSymbol))
 	globalsEnd   = uintptr(unsafe.Pointer(&heapStartSymbol))
 )

+const wasmPageSize = 64 * 1024
+
 func align(ptr uintptr) uintptr {
 	// Align to 16, which is the alignment of max_align_t:
 	// https://godbolt.org/z/dYqTsWrGq
@@ -73,67 +48,77 @@ func getCurrentStackPointer() uintptr
 // otherwise.
 func growHeap() bool {
 	// Grow memory by the available size, which means the heap size is doubled.
-	memorySize := wasm_memory_size(wasmMemoryIndex)
-	result := wasm_memory_grow(wasmMemoryIndex, memorySize)
+	memorySize := wasm_memory_size(0)
+	result := wasm_memory_grow(0, memorySize)
 	if result == -1 {
 		// Grow failed.
 		return false
 	}

-	setHeapEnd(uintptr(wasm_memory_size(wasmMemoryIndex) * wasmPageSize))
+	setHeapEnd(uintptr(wasm_memory_size(0) * wasmPageSize))

 	// Heap has grown successfully.
 	return true
 }

 // The below functions override the default allocator of wasi-libc. This ensures
-// code linked from other languages can allocate memory without colliding with
-// our GC allocations.
+// code linked from other languages can allocate memory on the same heap as the
+// TinyGo heap.

-var allocs = make(map[uintptr][]byte)
+// Keep track of all the heap allocations while they're in use.
+// This is not the most efficient solution but it costs a lot less in code size
+// compared to a map.
+var allocs []unsafe.Pointer
+
+func trackAlloc(ptr unsafe.Pointer) {
+	// Try to find some empty space in the allocs slice.
+	for i, slot := range allocs {
+		if slot == nil {
+			allocs[i] = slot
+			return
+		}
+	}
+	// Couldn't find this space. Fall back to appending to the end.
+	allocs = append(allocs, ptr)
+}
+
+func removeAlloc(ptr unsafe.Pointer) {
+	// Remove the pointer so it can be garbage collected.
+	for i, slot := range allocs {
+		if ptr == slot {
+			allocs[i] = nil
+			return
+		}
+	}
+}

 //export malloc
 func libc_malloc(size uintptr) unsafe.Pointer {
-	buf := make([]byte, size)
-	ptr := unsafe.Pointer(&buf[0])
-	allocs[uintptr(ptr)] = buf
+	ptr := alloc(size, nil)
+	trackAlloc(ptr)
 	return ptr
 }

 //export free
 func libc_free(ptr unsafe.Pointer) {
-	if ptr == nil {
-		return
-	}
-	if _, ok := allocs[uintptr(ptr)]; ok {
-		delete(allocs, uintptr(ptr))
-	} else {
-		panic("free: invalid pointer")
-	}
+	removeAlloc(ptr)
+	free(ptr)
 }

 //export calloc
 func libc_calloc(nmemb, size uintptr) unsafe.Pointer {
-	// No difference between calloc and malloc.
+	// Note: we could be even more correct here and check that nmemb * size
+	// doesn't overflow. However the current implementation should normally work
+	// fine.
 	return libc_malloc(nmemb * size)
 }

 //export realloc
 func libc_realloc(oldPtr unsafe.Pointer, size uintptr) unsafe.Pointer {
-	// It's hard to optimize this to expand the current buffer with our GC, but
-	// it is theoretically possible. For now, just always allocate fresh.
-	buf := make([]byte, size)
-
-	if oldPtr != nil {
-		if oldBuf, ok := allocs[uintptr(oldPtr)]; ok {
-			copy(buf, oldBuf)
-			delete(allocs, uintptr(oldPtr))
-		} else {
-			panic("realloc: invalid pointer")
-		}
+	newPtr := realloc(oldPtr, size)
+	if newPtr != oldPtr {
+		removeAlloc(oldPtr)
+		trackAlloc(newPtr)
 	}
-
-	ptr := unsafe.Pointer(&buf[0])
-	allocs[uintptr(ptr)] = buf
-	return ptr
+	return newPtr
 }
@@ -1,9 +0,0 @@
-//go:build runtime_asserts
-
-package runtime
-
-// enable assertions for the garbage collector
-const gcAsserts = true
-
-// enable asserts for the scheduler
-const schedulerAsserts = true
@@ -1,9 +0,0 @@
-//go:build !runtime_asserts
-
-package runtime
-
-// disable assertions for the garbage collector
-const gcAsserts = false
-
-// disable assertions for the scheduler
-const schedulerAsserts = false
@@ -25,9 +25,7 @@ package runtime
 // heapStart..metadataStart.
 //
 // More information:
-// https://aykevl.nl/2020/09/gc-tinygo
 // https://github.com/micropython/micropython/wiki/Memory-Manager
-// https://github.com/micropython/micropython/blob/master/py/gc.c
 // "The Garbage Collection Handbook" by Richard Jones, Antony Hosking, Eliot
 // Moss.

@@ -37,7 +35,11 @@ import (
 	"unsafe"
 )

-const gcDebug = false
+// Set gcDebug to true to print debug information.
+const (
+	gcDebug   = false   // print debug info
+	gcAsserts = gcDebug // perform sanity checks
+)

 // Some globals + constants for the entire GC.

@@ -286,14 +288,7 @@ func alloc(size uintptr, layout unsafe.Pointer) unsafe.Pointer {
 				// could be found. Run a garbage collection cycle to reclaim
 				// free memory and try again.
 				heapScanCount = 2
-				freeBytes := runGC()
-				heapSize := uintptr(metadataStart) - heapStart
-				if freeBytes < heapSize/3 {
-					// Ensure there is at least 33% headroom.
-					// This percentage was arbitrarily chosen, and may need to
-					// be tuned in the future.
-					growHeap()
-				}
+				GC()
 			} else {
 				// Even after garbage collection, no free memory could be found.
 				// Try to increase heap size.
@@ -384,13 +379,6 @@ func free(ptr unsafe.Pointer) {

 // GC performs a garbage collection cycle.
 func GC() {
-	runGC()
-}
-
-// runGC performs a garbage colleciton cycle. It is the internal implementation
-// of the runtime.GC() function. The difference is that it returns the number of
-// free bytes in the heap after the GC is finished.
-func runGC() (freeBytes uintptr) {
 	if gcDebug {
 		println("running collection cycle...")
 	}
@@ -432,14 +420,12 @@ func runGC() (freeBytes uintptr) {

 	// Sweep phase: free all non-marked objects and unmark marked objects for
 	// the next collection cycle.
-	freeBytes = sweep()
+	sweep()

 	// Show how much has been sweeped, for debugging.
 	if gcDebug {
 		dumpHeap()
 	}
-
-	return
 }

 // markRoots reads all pointers from start to end (exclusive) and if they look
@@ -582,8 +568,7 @@ func markRoot(addr, root uintptr) {
 }

 // Sweep goes through all memory and frees unmarked memory.
-// It returns how many bytes are free in the heap after the sweep.
-func sweep() (freeBytes uintptr) {
+func sweep() {
 	freeCurrentObject := false
 	for block := gcBlock(0); block < endBlock; block++ {
 		switch block.state() {
@@ -592,13 +577,11 @@ func sweep() (freeBytes uintptr) {
 			block.markFree()
 			freeCurrentObject = true
 			gcFrees++
-			freeBytes += bytesPerBlock
 		case blockStateTail:
 			if freeCurrentObject {
 				// This is a tail object following an unmarked head.
 				// Free it now.
 				block.markFree()
-				freeBytes += bytesPerBlock
 			}
 		case blockStateMark:
 			// This is a marked object. The next tail blocks must not be freed,
@@ -606,11 +589,8 @@ func sweep() (freeBytes uintptr) {
 			// collect this object if it is unreferenced then.
 			block.unmark()
 			freeCurrentObject = false
-		case blockStateFree:
-			freeBytes += bytesPerBlock
 		}
 	}
-	return
 }

 // looksLikePointer returns whether this could be a pointer. Currently, it
@@ -11,6 +11,8 @@ import (
 	"unsafe"
 )

+const gcAsserts = false // perform sanity checks
+
 // Ever-incrementing pointer: no memory is freed.
 var heapptr = heapStart

@@ -11,6 +11,8 @@ import (
 	"unsafe"
 )

+const gcAsserts = false // perform sanity checks
+
 var gcTotalAlloc uint64 // for runtime.MemStats
 var gcMallocs uint64
 var gcFrees uint64
@@ -1,6 +1,6 @@
 {
    "inherits": ["nrf52840", "nrf52840-s140v6-uf2"],
    "build-tags": ["circuitplay_bluefruit"],
-    "serial-port": ["acm:239a:8045"],
+    "serial-port": ["acm:239a:8045", "acm:239a:45"],
    "msd-volume-name": "CPLAYBTBOOT"
 }
@@ -3,7 +3,7 @@
    "build-tags": ["circuitplay_express"],
    "flash-1200-bps-reset": "true",
    "flash-method": "msd",
-    "serial-port": ["acm:239a:8018"],
+    "serial-port": ["acm:239a:8018", "acm:239a:18"],
    "msd-volume-name": "CPLAYBOOT",
    "msd-firmware-name": "firmware.uf2"
 }
@@ -1,6 +1,6 @@
 {
    "inherits": ["nrf52840", "nrf52840-s140v6-uf2"],
    "build-tags": ["clue_alpha"],
-    "serial-port": ["acm:239a:8072", "acm:239a:8071"],
+    "serial-port": ["acm:239a:8072", "acm:239a:0072", "acm:239a:0071", "acm:239a:8071"],
    "msd-volume-name": "CLUEBOOT"
 }
@@ -2,7 +2,7 @@
    "inherits": ["atsamd21g18a"],
    "build-tags": ["feather_m0"],
    "serial": "usb",
-    "serial-port": ["acm:239a:801b", "acm:239a:800b"],
+    "serial-port": ["acm:239a:801b", "acm:239a:001b", "acm:239a:800b", "acm:239a:000b", "acm:239a:0015"],
    "flash-1200-bps-reset": "true",
    "flash-method": "msd",
    "msd-volume-name": "FEATHERBOOT",
@@ -2,7 +2,7 @@
    "inherits": ["atsame51j19a"],
    "build-tags": ["feather_m4_can"],
    "serial": "usb",
-    "serial-port": ["acm:239a:80cd"],
+    "serial-port": ["acm:239a:80cd", "acm:239a:00cd"],
    "flash-1200-bps-reset": "true",
    "flash-method": "msd",
    "msd-volume-name": "FTHRCANBOOT",
@@ -2,7 +2,7 @@
    "inherits": ["atsamd51j19a"],
    "build-tags": ["feather_m4"],
    "serial": "usb",
-    "serial-port": ["acm:239a:8022"],
+    "serial-port": ["acm:239a:8022", "acm:239a:0022"],
    "flash-1200-bps-reset": "true",
    "flash-method": "msd",
    "msd-volume-name": "FEATHERBOOT",
@@ -1,6 +1,6 @@
 {
    "inherits": ["nrf52840", "nrf52840-s140v6-uf2"],
    "build-tags": ["feather_nrf52840_sense"],
-    "serial-port": ["acm:239a:8087", "acm:239a:8088"],
+    "serial-port": ["acm:239a:8087", "acm:239a:0087", "acm:239a:0088", "acm:239a:8088"],
    "msd-volume-name": "FTHRSNSBOOT"
 }
@@ -1,6 +1,6 @@
 {
    "inherits": ["nrf52840", "nrf52840-s140v6-uf2"],
    "build-tags": ["feather_nrf52840"],
-    "serial-port": ["acm:239a:8029", "acm:239a:802a"],
+    "serial-port": ["acm:239a:8029", "acm:239a:0029", "acm:239a:002a", "acm:239a:802a"],
    "msd-volume-name": "FTHR840BOOT"
 }
@@ -2,7 +2,7 @@
    "inherits": ["atsamd51p20a"],
    "build-tags": ["grandcentral_m4"],
    "serial": "usb",
-    "serial-port": ["acm:239a:8031"],
+    "serial-port": ["acm:239a:8031", "acm:239a:0031", "acm:239a:0032"],
    "flash-1200-bps-reset": "true",
    "flash-method": "msd",
    "msd-volume-name": "GCM4BOOT",
@@ -2,7 +2,7 @@
    "inherits": ["atsamd21g18a"],
    "build-tags": ["itsybitsy_m0"],
    "serial": "usb",
-    "serial-port": ["acm:239a:800f", "acm:239a:8012"],
+    "serial-port": ["acm:239a:800f", "acm:239a:000f", "acm:239a:8012"],
    "flash-1200-bps-reset": "true",
    "flash-method": "msd",
    "msd-volume-name": "ITSYBOOT",
@@ -4,7 +4,7 @@
    "serial": "usb",
    "flash-1200-bps-reset": "true",
    "flash-method": "msd",
-    "serial-port": ["acm:239a:802b"],
+    "serial-port": ["acm:239a:802b", "acm:239a:002b"],
    "msd-volume-name": "ITSYM4BOOT",
    "msd-firmware-name": "firmware.uf2"
 }
@@ -1,6 +1,6 @@
 {
    "inherits": ["nrf52840", "nrf52840-s140v6-uf2"],
    "build-tags": ["itsybitsy_nrf52840"],
-    "serial-port": ["acm:239A:8052", "acm:239A:8051"],
+    "serial-port": ["acm:239A:8052", "acm:239A:0052", "acm:239A:0051", "acm:239A:8051"],
    "msd-volume-name": "ITSY840BOOT"
 }
@@ -2,7 +2,7 @@
    "inherits": ["atsamd51j19a"],
    "build-tags": ["matrixportal_m4"],
    "serial": "usb",
-    "serial-port": ["acm:239a:80c9", "acm:239a:80ca"],
+    "serial-port": ["acm:239a:80c9", "acm:239a:00c9", "acm:239a:80ca"],
    "flash-1200-bps-reset": "true",
    "flash-method": "msd",
    "msd-volume-name": "MATRIXBOOT",
@@ -1,6 +1,6 @@
 {
    "inherits": ["nrf52840", "nrf52840-s140v6-uf2"],
    "build-tags": ["mdbt50qrx"],
-    "serial-port": ["acm:239a:810b", "acm:239a:810c"],
+    "serial-port": ["acm:239a:810b", "acm:239a:010b", "acm:239a:810c"],
    "msd-volume-name": "MDBT50QBOOT"
 }
@@ -2,7 +2,7 @@
    "inherits": ["atsamd51j19a"],
    "build-tags": ["metro_m4_airlift"],
    "serial": "usb",
-    "serial-port": ["acm:239A:8037"],
+    "serial-port": ["acm:239A:8037", "acm:239A:0037"],
    "flash-1200-bps-reset": "true",
    "flash-method": "msd",
    "msd-volume-name": "METROM4BOOT",
@@ -4,7 +4,7 @@
    "serial": "usb",
    "flash-1200-bps-reset": "true",
    "flash-method": "msd",
-    "serial-port": ["acm:239a:8033"],
+    "serial-port": ["acm:239a:8033", "acm:239a:33"],
    "msd-volume-name": "PYBADGEBOOT",
    "msd-firmware-name": "arcade.uf2"
 }
@@ -2,7 +2,7 @@
    "inherits": ["atsamd51j19a"],
    "build-tags": ["pygamer"],
    "serial": "usb",
-    "serial-port": ["acm:239a:803d", "acm:239a:803e"],
+    "serial-port": ["acm:239a:803d", "acm:239a:003d", "acm:239a:803e"],
    "flash-1200-bps-reset": "true",
    "flash-method": "msd",
    "msd-volume-name": "PYGAMERBOOT",
--- a/Show More
+++ b/Show More