cgo: allow --export= in LDFLAGS

This allows people to export some functions, such as malloc. Example: // #cgo LDFLAGS: --export=malloc import "C" This exports the function malloc. Note that this is somewhat unsafe right now, but it is used regardless. By using this workaround, people have some time to transition away from using malloc/free directly or until malloc is made safe to be used in this way.
wasm: do not export malloc, calloc, realloc, free
2026-07-29 16:18:41 +00:00 · 2022-09-15 11:36:29 +02:00 · 2022-09-15 11:36:26 +02:00
135 changed files with 666 additions and 925 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
@@ -1,5 +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,
 	}
@@ -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),
 	}
@@ -1124,11 +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
 }
@@ -1152,7 +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
@@ -1160,39 +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$funcaddr unsafe.Pointer
@@ -1200,7 +1162,7 @@ extern __typeof(%s) %s __attribute__((alias(%#v)));
 			Tok: token.VAR,
 			Specs: []ast.Spec{
 				&ast.ValueSpec{
-					Names: []*ast.Ident{{Name: node.Name.Name + "$funcaddr"}},
+					Names: []*ast.Ident{{Name: "C." + name + "$funcaddr"}},
 					Type: &ast.SelectorExpr{
 						X:   &ast.Ident{Name: "unsafe"},
 						Sel: &ast.Ident{Name: "Pointer"},
@@ -1209,10 +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},
@@ -1226,8 +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
@@ -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);
 }
@@ -142,6 +142,7 @@ var validLinkerFlags = []*regexp.Regexp{
 	re(`-L([^@\-].*)`),
 	re(`-O`),
 	re(`-O([^@\-].*)`),
+	re(`--export=(.+)`), // for wasm-ld
 	re(`-f(no-)?(pic|PIC|pie|PIE)`),
 	re(`-f(no-)?openmp(-simd)?`),
 	re(`-fsanitize=([^@\-].*)`),
@@ -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
@@ -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.
@@ -1059,11 +1059,12 @@ func (b *builder) createFunctionStart(intrinsic bool) {
 	if b.info.section != "" {
 		b.llvmFn.SetSection(b.info.section)
 	}
-	if b.info.exported && strings.HasPrefix(b.Triple, "wasm") {
+	if b.info.exported && b.info.module != "" && strings.HasPrefix(b.Triple, "wasm") {
 		// Set the exported name. This is necessary for WebAssembly because
 		// otherwise the function is not exported.
-		functionAttr := b.ctx.CreateStringAttribute("wasm-export-name", b.info.linkName)
-		b.llvmFn.AddFunctionAttr(functionAttr)
+		b.llvmFn.AddFunctionAttr(b.ctx.CreateStringAttribute("wasm-export-name", b.info.linkName))
+		// Set the export module.
+		b.llvmFn.AddFunctionAttr(b.ctx.CreateStringAttribute("wasm-export-module", b.info.module))
 	}

 	// Some functions have a pragma controlling the inlining level.
@@ -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)
@@ -210,8 +210,9 @@ func (c *compilerContext) getFunction(fn *ssa.Function) llvm.Value {
 // exported.
 func (c *compilerContext) getFunctionInfo(f *ssa.Function) functionInfo {
 	info := functionInfo{
-		// Pick the default linkName.
-		linkName: f.RelString(nil),
+		module:     "env",
+		importName: f.Name(),
+		linkName:   f.RelString(nil), // pick the default linkName
 	}
 	// Check for //go: pragmas, which may change the link name (among others).
 	info.parsePragmas(f)
@@ -225,10 +226,6 @@ func (info *functionInfo) parsePragmas(f *ssa.Function) {
 		return
 	}
 	if decl, ok := f.Syntax().(*ast.FuncDecl); ok && decl.Doc != nil {
-
-		// Our importName for a wasm module (if we are compiling to wasm), or llvm link name
-		var importName string
-
 		for _, comment := range decl.Doc.List {
 			text := comment.Text
 			if strings.HasPrefix(text, "//export ") {
@@ -246,7 +243,8 @@ func (info *functionInfo) parsePragmas(f *ssa.Function) {
 					continue
 				}

-				importName = parts[1]
+				info.importName = parts[1]
+				info.linkName = parts[1]
 				info.exported = true
 			case "//go:interrupt":
 				if hasUnsafeImport(f.Pkg.Pkg) {
@@ -254,10 +252,13 @@ func (info *functionInfo) parsePragmas(f *ssa.Function) {
 				}
 			case "//go:wasm-module":
 				// Alternative comment for setting the import module.
-				if len(parts) != 2 {
-					continue
+				if len(parts) == 1 {
+					// Function must not be exported outside of the WebAssembly
+					// module (but only be made available for linking).
+					info.module = ""
+				} else if len(parts) == 2 {
+					info.module = parts[1]
 				}
-				info.module = parts[1]
 			case "//go:inline":
 				info.inline = inlineHint
 			case "//go:noinline":
@@ -297,17 +298,6 @@ func (info *functionInfo) parsePragmas(f *ssa.Function) {
 				}
 			}
 		}
-
-		// Set the importName for our exported function if we have one
-		if importName != "" {
-			if info.module == "" {
-				info.linkName = importName
-			} else {
-				// WebAssembly import
-				info.importName = importName
-			}
-		}
-
 	}
 }

@@ -62,7 +62,7 @@ declare void @main.undefinedFunctionNotInSection(i8*) #0

 attributes #0 = { "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" }
 attributes #1 = { nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" }
-attributes #2 = { nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" "wasm-export-name"="extern_func" "wasm-import-module"="env" "wasm-import-name"="extern_func" }
+attributes #2 = { nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" "wasm-export-module"="env" "wasm-export-name"="extern_func" "wasm-import-module"="env" "wasm-import-name"="extern_func" }
 attributes #3 = { inlinehint nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" }
 attributes #4 = { noinline nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" }
-attributes #5 = { nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" "wasm-export-name"="exportedFunctionInSection" "wasm-import-module"="env" "wasm-import-name"="exportedFunctionInSection" }
+attributes #5 = { nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" "wasm-export-module"="env" "wasm-export-name"="exportedFunctionInSection" "wasm-import-module"="env" "wasm-import-name"="exportedFunctionInSection" }
@@ -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=
@@ -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 (
@@ -4,7 +4,7 @@
 package machine

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

 // Digital pins
 const (
@@ -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"
 )
@@ -17,20 +18,20 @@ import (
 const deviceName = sam.Device

 const (
+	PinAnalog    PinMode = 1
+	PinSERCOM    PinMode = 2
+	PinSERCOMAlt PinMode = 3
+	PinTimer     PinMode = 4
+	PinTimerAlt  PinMode = 5
+	PinCom       PinMode = 6
+	//PinAC_CLK        PinMode = 7
+	PinDigital       PinMode = 8
 	PinInput         PinMode = 9
 	PinInputPullup   PinMode = 10
 	PinOutput        PinMode = 11
+	PinTCC           PinMode = PinTimer
+	PinTCCAlt        PinMode = PinTimerAlt
 	PinInputPulldown PinMode = 12
-
-	// internal pin modes
-	pinAnalog    PinMode = 1
-	pinSERCOM    PinMode = 2
-	pinSERCOMAlt PinMode = 3
-	pinTCC       PinMode = 4
-	pinTCCAlt    PinMode = 5
-	pinCom       PinMode = 6
-	//PinAC_CLK        PinMode = 7
-	pinDigital PinMode = 8
 )

 type PinChange uint8
@@ -149,7 +150,7 @@ func findPinPadMapping(sercom uint8, pin Pin) (pinMode PinMode, pad uint32, ok b
 	if upper != 0 {
 		// SERCOM
 		if (upper>>1)-1 == sercom {
-			pinMode = pinSERCOM
+			pinMode = PinSERCOM
 			pad |= uint32((upper & 1) << 1)
 			ok = true
 		}
@@ -157,7 +158,7 @@ func findPinPadMapping(sercom uint8, pin Pin) (pinMode PinMode, pad uint32, ok b
 	if lower != 0 {
 		// SERCOM-ALT
 		if (lower>>1)-1 == sercom {
-			pinMode = pinSERCOMAlt
+			pinMode = PinSERCOMAlt
 			pad |= uint32((lower & 1) << 1)
 			ok = true
 		}
@@ -381,7 +382,7 @@ func (a ADC) Configure(config ADCConfig) {
 	// 1/2 VDDANA = 0.5 * 3V3 = 1.65V
 	sam.ADC.REFCTRL.SetBits(sam.ADC_REFCTRL_REFSEL_INTVCC1 << sam.ADC_REFCTRL_REFSEL_Pos)

-	a.Pin.Configure(PinConfig{Mode: pinAnalog})
+	a.Pin.Configure(PinConfig{Mode: PinAnalog})
 	return
 }

@@ -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
@@ -1000,11 +1001,11 @@ func (i2s I2S) Configure(config I2SConfig) {
 	}

 	// configure pin for clock
-	config.SCK.Configure(PinConfig{Mode: pinCom})
+	config.SCK.Configure(PinConfig{Mode: PinCom})

 	// configure pin for WS, if needed
 	if config.WS != NoPin {
-		config.WS.Configure(PinConfig{Mode: pinCom})
+		config.WS.Configure(PinConfig{Mode: PinCom})
 	}

 	// now set serializer data size.
@@ -1043,7 +1044,7 @@ func (i2s I2S) Configure(config I2SConfig) {
 	}

 	// configure data pin
-	config.SD.Configure(PinConfig{Mode: pinCom})
+	config.SD.Configure(PinConfig{Mode: PinCom})

 	// re-enable
 	i2s.Bus.CTRLA.SetBits(sam.I2S_CTRLA_ENABLE)
@@ -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.
@@ -1636,12 +1641,12 @@ func findPinTimerMapping(timer uint8, pin Pin) (PinMode, uint8) {
 	if mapping&0x07 == timer+1 {
 		// PWM output is on peripheral function E.
 		evenChannel := ((mapping >> 3) & 1) * 2
-		return pinTCC, evenChannel + uint8(pin&1)
+		return PinTCC, evenChannel + uint8(pin&1)
 	}
 	if (mapping&0x70)>>4 == timer+1 {
 		// PWM output is on peripheral function F.
 		evenChannel := ((mapping >> 7) & 1) * 2
-		return pinTCCAlt, evenChannel + uint8(pin&1)
+		return PinTCCAlt, evenChannel + uint8(pin&1)
 	}
 	return 0, 0
 }
@@ -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()
 }
@@ -37,8 +37,8 @@ func (dev *USBDevice) Configure(config UARTConfig) {
 	sam.USB_DEVICE.DESCADD.Set(uint32(uintptr(unsafe.Pointer(&usbEndpointDescriptors))))

 	// configure pins
-	USBCDC_DM_PIN.Configure(PinConfig{Mode: pinCom})
-	USBCDC_DP_PIN.Configure(PinConfig{Mode: pinCom})
+	USBCDC_DM_PIN.Configure(PinConfig{Mode: PinCom})
+	USBCDC_DP_PIN.Configure(PinConfig{Mode: PinCom})

 	// performs pad calibration from store fuses
 	handlePadCalibration()
@@ -86,53 +86,53 @@ func (p Pin) Configure(config PinConfig) {
 		sam.PORT.OUTSET0.Set(1 << uint8(p))
 		p.setPinCfg(sam.PORT_PINCFG0_INEN | sam.PORT_PINCFG0_PULLEN)

-	case pinSERCOM:
+	case PinSERCOM:
 		if uint8(p)&1 > 0 {
 			// odd pin, so save the even pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXE_Msk
-			p.setPMux(val | (uint8(pinSERCOM) << sam.PORT_PMUX0_PMUXO_Pos))
+			p.setPMux(val | (uint8(PinSERCOM) << sam.PORT_PMUX0_PMUXO_Pos))
 		} else {
 			// even pin, so save the odd pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXO_Msk
-			p.setPMux(val | (uint8(pinSERCOM) << sam.PORT_PMUX0_PMUXE_Pos))
+			p.setPMux(val | (uint8(PinSERCOM) << sam.PORT_PMUX0_PMUXE_Pos))
 		}
 		// enable port config
 		p.setPinCfg(sam.PORT_PINCFG0_PMUXEN | sam.PORT_PINCFG0_DRVSTR | sam.PORT_PINCFG0_INEN)

-	case pinSERCOMAlt:
+	case PinSERCOMAlt:
 		if uint8(p)&1 > 0 {
 			// odd pin, so save the even pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXE_Msk
-			p.setPMux(val | (uint8(pinSERCOMAlt) << sam.PORT_PMUX0_PMUXO_Pos))
+			p.setPMux(val | (uint8(PinSERCOMAlt) << sam.PORT_PMUX0_PMUXO_Pos))
 		} else {
 			// even pin, so save the odd pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXO_Msk
-			p.setPMux(val | (uint8(pinSERCOMAlt) << sam.PORT_PMUX0_PMUXE_Pos))
+			p.setPMux(val | (uint8(PinSERCOMAlt) << sam.PORT_PMUX0_PMUXE_Pos))
 		}
 		// enable port config
 		p.setPinCfg(sam.PORT_PINCFG0_PMUXEN | sam.PORT_PINCFG0_DRVSTR)

-	case pinCom:
+	case PinCom:
 		if uint8(p)&1 > 0 {
 			// odd pin, so save the even pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXE_Msk
-			p.setPMux(val | (uint8(pinCom) << sam.PORT_PMUX0_PMUXO_Pos))
+			p.setPMux(val | (uint8(PinCom) << sam.PORT_PMUX0_PMUXO_Pos))
 		} else {
 			// even pin, so save the odd pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXO_Msk
-			p.setPMux(val | (uint8(pinCom) << sam.PORT_PMUX0_PMUXE_Pos))
+			p.setPMux(val | (uint8(PinCom) << sam.PORT_PMUX0_PMUXE_Pos))
 		}
 		// enable port config
 		p.setPinCfg(sam.PORT_PINCFG0_PMUXEN)
-	case pinAnalog:
+	case PinAnalog:
 		if uint8(p)&1 > 0 {
 			// odd pin, so save the even pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXE_Msk
-			p.setPMux(val | (uint8(pinAnalog) << sam.PORT_PMUX0_PMUXO_Pos))
+			p.setPMux(val | (uint8(PinAnalog) << sam.PORT_PMUX0_PMUXO_Pos))
 		} else {
 			// even pin, so save the odd pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXO_Msk
-			p.setPMux(val | (uint8(pinAnalog) << sam.PORT_PMUX0_PMUXE_Pos))
+			p.setPMux(val | (uint8(PinAnalog) << sam.PORT_PMUX0_PMUXE_Pos))
 		}
 		// enable port config
 		p.setPinCfg(sam.PORT_PINCFG0_PMUXEN | sam.PORT_PINCFG0_DRVSTR)
@@ -137,53 +137,53 @@ func (p Pin) Configure(config PinConfig) {
 			p.setPinCfg(sam.PORT_PINCFG0_INEN | sam.PORT_PINCFG0_PULLEN)
 		}

-	case pinSERCOM:
+	case PinSERCOM:
 		if p&1 > 0 {
 			// odd pin, so save the even pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXE_Msk
-			p.setPMux(val | (uint8(pinSERCOM) << sam.PORT_PMUX0_PMUXO_Pos))
+			p.setPMux(val | (uint8(PinSERCOM) << sam.PORT_PMUX0_PMUXO_Pos))
 		} else {
 			// even pin, so save the odd pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXO_Msk
-			p.setPMux(val | (uint8(pinSERCOM) << sam.PORT_PMUX0_PMUXE_Pos))
+			p.setPMux(val | (uint8(PinSERCOM) << sam.PORT_PMUX0_PMUXE_Pos))
 		}
 		// enable port config
 		p.setPinCfg(sam.PORT_PINCFG0_PMUXEN | sam.PORT_PINCFG0_DRVSTR | sam.PORT_PINCFG0_INEN)

-	case pinSERCOMAlt:
+	case PinSERCOMAlt:
 		if p&1 > 0 {
 			// odd pin, so save the even pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXE_Msk
-			p.setPMux(val | (uint8(pinSERCOMAlt) << sam.PORT_PMUX0_PMUXO_Pos))
+			p.setPMux(val | (uint8(PinSERCOMAlt) << sam.PORT_PMUX0_PMUXO_Pos))
 		} else {
 			// even pin, so save the odd pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXO_Msk
-			p.setPMux(val | (uint8(pinSERCOMAlt) << sam.PORT_PMUX0_PMUXE_Pos))
+			p.setPMux(val | (uint8(PinSERCOMAlt) << sam.PORT_PMUX0_PMUXE_Pos))
 		}
 		// enable port config
 		p.setPinCfg(sam.PORT_PINCFG0_PMUXEN | sam.PORT_PINCFG0_DRVSTR)

-	case pinCom:
+	case PinCom:
 		if p&1 > 0 {
 			// odd pin, so save the even pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXE_Msk
-			p.setPMux(val | (uint8(pinCom) << sam.PORT_PMUX0_PMUXO_Pos))
+			p.setPMux(val | (uint8(PinCom) << sam.PORT_PMUX0_PMUXO_Pos))
 		} else {
 			// even pin, so save the odd pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXO_Msk
-			p.setPMux(val | (uint8(pinCom) << sam.PORT_PMUX0_PMUXE_Pos))
+			p.setPMux(val | (uint8(PinCom) << sam.PORT_PMUX0_PMUXE_Pos))
 		}
 		// enable port config
 		p.setPinCfg(sam.PORT_PINCFG0_PMUXEN)
-	case pinAnalog:
+	case PinAnalog:
 		if p&1 > 0 {
 			// odd pin, so save the even pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXE_Msk
-			p.setPMux(val | (uint8(pinAnalog) << sam.PORT_PMUX0_PMUXO_Pos))
+			p.setPMux(val | (uint8(PinAnalog) << sam.PORT_PMUX0_PMUXO_Pos))
 		} else {
 			// even pin, so save the odd pins
 			val := p.getPMux() & sam.PORT_PMUX0_PMUXO_Msk
-			p.setPMux(val | (uint8(pinAnalog) << sam.PORT_PMUX0_PMUXE_Pos))
+			p.setPMux(val | (uint8(PinAnalog) << sam.PORT_PMUX0_PMUXE_Pos))
 		}
 		// enable port config
 		p.setPinCfg(sam.PORT_PINCFG0_PMUXEN | sam.PORT_PINCFG0_DRVSTR)
@@ -10,6 +10,7 @@ package machine
 import (
 	"device/arm"
 	"device/sam"
+	"errors"
 	"runtime/interrupt"
 	"unsafe"
 )
@@ -21,29 +22,30 @@ func CPUFrequency() uint32 {
 }

 const (
+	PinAnalog        PinMode = 1
+	PinSERCOM        PinMode = 2
+	PinSERCOMAlt     PinMode = 3
+	PinTimer         PinMode = 4
+	PinTimerAlt      PinMode = 5
+	PinTCCPDEC       PinMode = 6
+	PinCom           PinMode = 7
+	PinSDHC          PinMode = 8
+	PinI2S           PinMode = 9
+	PinPCC           PinMode = 10
+	PinGMAC          PinMode = 11
+	PinACCLK         PinMode = 12
+	PinCCL           PinMode = 13
+	PinDigital       PinMode = 14
 	PinInput         PinMode = 15
 	PinInputPullup   PinMode = 16
 	PinOutput        PinMode = 17
+	PinTCCE          PinMode = PinTimer
+	PinTCCF          PinMode = PinTimerAlt
+	PinTCCG          PinMode = PinTCCPDEC
 	PinInputPulldown PinMode = 18
-
-	// internal pin modes
-	pinAnalog    PinMode = 1
-	pinSERCOM    PinMode = 2
-	pinSERCOMAlt PinMode = 3
-	pinTCCE      PinMode = 4
-	pinTCCF      PinMode = 5
-	pinTCCG      PinMode = 6
-	pinCom       PinMode = 7
-	pinSDHC      PinMode = 8
-	pinI2S       PinMode = 9
-	pinPCC       PinMode = 10
-	pinGMAC      PinMode = 11
-	pinACCLK     PinMode = 12
-	pinCCL       PinMode = 13
-	pinDigital   PinMode = 14
-	pinCAN       PinMode = 19
-	pinCAN0      PinMode = pinSDHC
-	pinCAN1      PinMode = pinCom
+	PinCAN           PinMode = 19
+	PinCAN0          PinMode = PinSDHC
+	PinCAN1          PinMode = PinCom
 )

 type PinChange uint8
@@ -337,7 +339,7 @@ func findPinPadMapping(sercom uint8, pin Pin) (pinMode PinMode, pad uint32, ok b
 	if upper != 0 {
 		// SERCOM
 		if (upper>>4)-1 == sercom {
-			pinMode = pinSERCOM
+			pinMode = PinSERCOM
 			pad |= uint32(upper % 4)
 			ok = true
 		}
@@ -345,7 +347,7 @@ func findPinPadMapping(sercom uint8, pin Pin) (pinMode PinMode, pad uint32, ok b
 	if lower != 0 {
 		// SERCOM-ALT
 		if (lower>>4)-1 == sercom {
-			pinMode = pinSERCOMAlt
+			pinMode = PinSERCOMAlt
 			pad |= uint32(lower % 4)
 			ok = true
 		}
@@ -579,65 +581,65 @@ func (p Pin) Configure(config PinConfig) {
 		sam.PORT.GROUP[group].OUTSET.Set(1 << pin_in_group)
 		p.setPinCfg(sam.PORT_GROUP_PINCFG_INEN | sam.PORT_GROUP_PINCFG_PULLEN)

-	case pinSERCOM:
+	case PinSERCOM:
 		if p&1 > 0 {
 			// odd pin, so save the even pins
 			val := p.getPMux() & sam.PORT_GROUP_PMUX_PMUXE_Msk
-			p.setPMux(val | (uint8(pinSERCOM) << sam.PORT_GROUP_PMUX_PMUXO_Pos))
+			p.setPMux(val | (uint8(PinSERCOM) << sam.PORT_GROUP_PMUX_PMUXO_Pos))
 		} else {
 			// even pin, so save the odd pins
 			val := p.getPMux() & sam.PORT_GROUP_PMUX_PMUXO_Msk
-			p.setPMux(val | (uint8(pinSERCOM) << sam.PORT_GROUP_PMUX_PMUXE_Pos))
+			p.setPMux(val | (uint8(PinSERCOM) << sam.PORT_GROUP_PMUX_PMUXE_Pos))
 		}
 		// enable port config
 		p.setPinCfg(sam.PORT_GROUP_PINCFG_PMUXEN | sam.PORT_GROUP_PINCFG_DRVSTR | sam.PORT_GROUP_PINCFG_INEN)

-	case pinSERCOMAlt:
+	case PinSERCOMAlt:
 		if p&1 > 0 {
 			// odd pin, so save the even pins
 			val := p.getPMux() & sam.PORT_GROUP_PMUX_PMUXE_Msk
-			p.setPMux(val | (uint8(pinSERCOMAlt) << sam.PORT_GROUP_PMUX_PMUXO_Pos))
+			p.setPMux(val | (uint8(PinSERCOMAlt) << sam.PORT_GROUP_PMUX_PMUXO_Pos))
 		} else {
 			// even pin, so save the odd pins
 			val := p.getPMux() & sam.PORT_GROUP_PMUX_PMUXO_Msk
-			p.setPMux(val | (uint8(pinSERCOMAlt) << sam.PORT_GROUP_PMUX_PMUXE_Pos))
+			p.setPMux(val | (uint8(PinSERCOMAlt) << sam.PORT_GROUP_PMUX_PMUXE_Pos))
 		}
 		// enable port config
 		p.setPinCfg(sam.PORT_GROUP_PINCFG_PMUXEN | sam.PORT_GROUP_PINCFG_DRVSTR)

-	case pinCom:
+	case PinCom:
 		if p&1 > 0 {
 			// odd pin, so save the even pins
 			val := p.getPMux() & sam.PORT_GROUP_PMUX_PMUXE_Msk
-			p.setPMux(val | (uint8(pinCom) << sam.PORT_GROUP_PMUX_PMUXO_Pos))
+			p.setPMux(val | (uint8(PinCom) << sam.PORT_GROUP_PMUX_PMUXO_Pos))
 		} else {
 			// even pin, so save the odd pins
 			val := p.getPMux() & sam.PORT_GROUP_PMUX_PMUXO_Msk
-			p.setPMux(val | (uint8(pinCom) << sam.PORT_GROUP_PMUX_PMUXE_Pos))
+			p.setPMux(val | (uint8(PinCom) << sam.PORT_GROUP_PMUX_PMUXE_Pos))
 		}
 		// enable port config
 		p.setPinCfg(sam.PORT_GROUP_PINCFG_PMUXEN)
-	case pinAnalog:
+	case PinAnalog:
 		if p&1 > 0 {
 			// odd pin, so save the even pins
 			val := p.getPMux() & sam.PORT_GROUP_PMUX_PMUXE_Msk
-			p.setPMux(val | (uint8(pinAnalog) << sam.PORT_GROUP_PMUX_PMUXO_Pos))
+			p.setPMux(val | (uint8(PinAnalog) << sam.PORT_GROUP_PMUX_PMUXO_Pos))
 		} else {
 			// even pin, so save the odd pins
 			val := p.getPMux() & sam.PORT_GROUP_PMUX_PMUXO_Msk
-			p.setPMux(val | (uint8(pinAnalog) << sam.PORT_GROUP_PMUX_PMUXE_Pos))
+			p.setPMux(val | (uint8(PinAnalog) << sam.PORT_GROUP_PMUX_PMUXE_Pos))
 		}
 		// enable port config
 		p.setPinCfg(sam.PORT_GROUP_PINCFG_PMUXEN | sam.PORT_GROUP_PINCFG_DRVSTR)
-	case pinSDHC:
+	case PinSDHC:
 		if p&1 > 0 {
 			// odd pin, so save the even pins
 			val := p.getPMux() & sam.PORT_GROUP_PMUX_PMUXE_Msk
-			p.setPMux(val | (uint8(pinSDHC) << sam.PORT_GROUP_PMUX_PMUXO_Pos))
+			p.setPMux(val | (uint8(PinSDHC) << sam.PORT_GROUP_PMUX_PMUXO_Pos))
 		} else {
 			// even pin, so save the odd pins
 			val := p.getPMux() & sam.PORT_GROUP_PMUX_PMUXO_Msk
-			p.setPMux(val | (uint8(pinSDHC) << sam.PORT_GROUP_PMUX_PMUXE_Pos))
+			p.setPMux(val | (uint8(PinSDHC) << sam.PORT_GROUP_PMUX_PMUXE_Pos))
 		}
 		// enable port config
 		p.setPinCfg(sam.PORT_GROUP_PINCFG_PMUXEN)
@@ -813,7 +815,7 @@ func (a ADC) Configure(config ADCConfig) {
 		adc.REFCTRL.SetBits(sam.ADC_REFCTRL_REFSEL_INTVCC1)
 	}

-	a.Pin.Configure(PinConfig{Mode: pinAnalog})
+	a.Pin.Configure(PinConfig{Mode: PinAnalog})
 }

 // Get returns the current value of a ADC pin, in the range 0..0xffff.
@@ -1149,7 +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.
@@ -1525,6 +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.
@@ -1866,7 +1872,7 @@ var pinTimerMapping = [...]struct{ F, G uint8 }{
 	PB02 / 2: {pinTCC2_2, 0},
 }

-// findPinPadMapping returns the pin mode (pinTCCF or pinTCCG) and the channel
+// findPinPadMapping returns the pin mode (PinTCCF or PinTCCG) and the channel
 // number for a given timer and pin. A zero PinMode is returned if no mapping
 // could be found.
 func findPinTimerMapping(timer uint8, pin Pin) (PinMode, uint8) {
@@ -1878,12 +1884,12 @@ func findPinTimerMapping(timer uint8, pin Pin) (PinMode, uint8) {

 	// Check for column F in the datasheet.
 	if mapping.F>>4-1 == timer {
-		return pinTCCF, mapping.F&0x0f + uint8(pin)&1
+		return PinTCCF, mapping.F&0x0f + uint8(pin)&1
 	}

 	// Check for column G in the datasheet.
 	if mapping.G>>4-1 == timer {
-		return pinTCCG, mapping.G&0x0f + uint8(pin)&1
+		return PinTCCG, mapping.G&0x0f + uint8(pin)&1
 	}

 	// Nothing found.
@@ -1974,7 +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()
 }
@@ -37,8 +37,8 @@ func (dev *USBDevice) Configure(config UARTConfig) {
 	sam.USB_DEVICE.DESCADD.Set(uint32(uintptr(unsafe.Pointer(&usbEndpointDescriptors))))

 	// configure pins
-	USBCDC_DM_PIN.Configure(PinConfig{Mode: pinCom})
-	USBCDC_DP_PIN.Configure(PinConfig{Mode: pinCom})
+	USBCDC_DM_PIN.Configure(PinConfig{Mode: PinCom})
+	USBCDC_DP_PIN.Configure(PinConfig{Mode: PinCom})

 	// performs pad calibration from store fuses
 	handlePadCalibration()
@@ -68,9 +68,9 @@ func (can *CAN) Configure(config CANConfig) error {
 		config.Standby.Low()
 	}

-	mode := pinCAN0
+	mode := PinCAN0
 	if can.instance() == 1 {
-		mode = pinCAN1
+		mode = PinCAN1
 	}

 	config.Rx.Configure(PinConfig{Mode: mode})
@@ -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
@@ -18,11 +18,9 @@ func CPUFrequency() uint32 {
 const (
 	PinInput PinMode = iota
 	PinOutput
-
-	// internal pin modes
-	pinPWM
-	pinSPI
-	pinI2C = pinSPI
+	PinPWM
+	PinSPI
+	PinI2C = PinSPI
 )

 // Configure this pin with the given configuration.
@@ -31,10 +29,10 @@ func (p Pin) Configure(config PinConfig) {
 	switch config.Mode {
 	case PinOutput:
 		sifive.GPIO0.OUTPUT_EN.SetBits(1 << uint8(p))
-	case pinPWM:
+	case PinPWM:
 		sifive.GPIO0.IOF_EN.SetBits(1 << uint8(p))
 		sifive.GPIO0.IOF_SEL.SetBits(1 << uint8(p))
-	case pinSPI:
+	case PinSPI:
 		sifive.GPIO0.IOF_EN.SetBits(1 << uint8(p))
 		sifive.GPIO0.IOF_SEL.ClearBits(1 << uint8(p))
 	}
@@ -147,9 +145,9 @@ func (spi SPI) Configure(config SPIConfig) error {
 	}

 	// enable pins for SPI
-	config.SCK.Configure(PinConfig{Mode: pinSPI})
-	config.SDO.Configure(PinConfig{Mode: pinSPI})
-	config.SDI.Configure(PinConfig{Mode: pinSPI})
+	config.SCK.Configure(PinConfig{Mode: PinSPI})
+	config.SDO.Configure(PinConfig{Mode: PinSPI})
+	config.SDI.Configure(PinConfig{Mode: PinSPI})

 	// set default frequency
 	if config.Frequency == 0 {
@@ -233,7 +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 {
@@ -253,8 +251,8 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	// enable controller
 	i2c.Bus.CTR.SetBits(sifive.I2C_CTR_EN)

-	config.SDA.Configure(PinConfig{Mode: pinI2C})
-	config.SCL.Configure(PinConfig{Mode: pinI2C})
+	config.SDA.Configure(PinConfig{Mode: PinI2C})
+	config.SCL.Configure(PinConfig{Mode: PinI2C})

 	return nil
 }
@@ -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 {
@@ -21,40 +21,36 @@ func CPUFrequency() uint32 {
 const (
 	// GPIO
 	PinInput PinMode = iota
-	PinInputPullup
-	PinInputPulldown
+	PinInputPullUp
+	PinInputPullDown
 	PinOutput
 	PinOutputOpenDrain
 	PinDisable

 	// ADC
-	pinInputAnalog
+	PinInputAnalog

 	// UART
-	pinModeUARTTX
-	pinModeUARTRX
+	PinModeUARTTX
+	PinModeUARTRX

 	// SPI
-	pinModeSPISDI
-	pinModeSPISDO
-	pinModeSPICLK
-	pinModeSPICS
+	PinModeSPISDI
+	PinModeSPISDO
+	PinModeSPICLK
+	PinModeSPICS

 	// I2C
-	pinModeI2CSDA
-	pinModeI2CSCL
-)
-
-// Deprecated: use PinInputPullup and PinInputPulldown instead.
-const (
-	PinInputPullUp   = PinInputPullup
-	PinInputPullDown = PinInputPulldown
+	PinModeI2CSDA
+	PinModeI2CSCL
 )

 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)

@@ -283,29 +279,29 @@ func (p Pin) Configure(config PinConfig) {
 		gpio.GDIR.ClearBits(p.getMask())
 		pad.Set(dse(7) | hys)

-	case pinInputAnalog:
+	case PinInputAnalog:
 		gpio.GDIR.ClearBits(p.getMask())
 		pad.Set(dse(7))

-	case pinModeUARTTX:
+	case PinModeUARTTX:
 		pad.Set(sre | dse(3) | spd(3))

-	case pinModeUARTRX:
+	case PinModeUARTRX:
 		pad.Set(dse(7) | pke | pue | pup(3) | hys)

-	case pinModeSPISDI:
+	case PinModeSPISDI:
 		pad.Set(dse(7) | spd(2))

-	case pinModeSPISDO:
+	case PinModeSPISDO:
 		pad.Set(dse(7) | spd(2))

-	case pinModeSPICLK:
+	case PinModeSPICLK:
 		pad.Set(dse(7) | spd(2))

-	case pinModeSPICS:
+	case PinModeSPICS:
 		pad.Set(dse(7))

-	case pinModeI2CSDA, pinModeI2CSCL:
+	case PinModeI2CSDA, PinModeI2CSCL:
 		pad.Set(ode | sre | dse(4) | spd(1) | pke | pue | pup(3))
 	}

@@ -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 {
@@ -759,7 +755,7 @@ func (p Pin) getMuxMode(config PinConfig) uint32 {
 		return mode

 	// ADC
-	case pinInputAnalog:
+	case PinInputAnalog:
 		mode := uint32(0x5) // use alternate function 5 (GPIO)
 		if forcePath {
 			mode |= 0x10 // SION bit
@@ -767,7 +763,7 @@ func (p Pin) getMuxMode(config PinConfig) uint32 {
 		return mode

 	// UART RX/TX
-	case pinModeUARTRX, pinModeUARTTX:
+	case PinModeUARTRX, PinModeUARTTX:
 		mode := uint32(0x2) // UART is usually alternate function 2 on Teensy 4.x
 		// Teensy 4.1 has a UART (LPUART5) with alternate function 1
 		if p == PB28 || p == PB29 {
@@ -776,7 +772,7 @@ func (p Pin) getMuxMode(config PinConfig) uint32 {
 		return mode

 	// SPI SDI
-	case pinModeSPISDI:
+	case PinModeSPISDI:
 		var mode uint32
 		switch p {
 		case PC15: // LPSPI1 SDI on PC15 alternate function 4
@@ -794,7 +790,7 @@ func (p Pin) getMuxMode(config PinConfig) uint32 {
 		return mode

 	// SPI SDO
-	case pinModeSPISDO:
+	case PinModeSPISDO:
 		var mode uint32
 		switch p {
 		case PC14: // LPSPI1 SDO on PC14 alternate function 4
@@ -812,7 +808,7 @@ func (p Pin) getMuxMode(config PinConfig) uint32 {
 		return mode

 	// SPI SCK
-	case pinModeSPICLK:
+	case PinModeSPICLK:
 		var mode uint32
 		switch p {
 		case PC12: // LPSPI1 SCK on PC12 alternate function 4
@@ -830,7 +826,7 @@ func (p Pin) getMuxMode(config PinConfig) uint32 {
 		return mode

 	// SPI CS
-	case pinModeSPICS:
+	case PinModeSPICS:
 		var mode uint32
 		switch p {
 		case PC13: // LPSPI1 CS on PC13 alternate function 4
@@ -848,7 +844,7 @@ func (p Pin) getMuxMode(config PinConfig) uint32 {
 		return mode

 	// I2C SDA
-	case pinModeI2CSDA:
+	case PinModeI2CSDA:
 		var mode uint32
 		switch p {
 		case PA13: // LPI2C4 SDA on PA13 alternate function 0
@@ -866,7 +862,7 @@ func (p Pin) getMuxMode(config PinConfig) uint32 {
 		return mode

 	// I2C SCL
-	case pinModeI2CSCL:
+	case PinModeI2CSCL:
 		var mode uint32
 		switch p {
 		case PA12: // LPI2C4 SCL on PA12 alternate function 0
@@ -902,7 +898,7 @@ func (a ADC) Configure(config ADCConfig) {
 		defaultSamples    = uint32(4)
 	)

-	a.Pin.Configure(PinConfig{Mode: pinInputAnalog})
+	a.Pin.Configure(PinConfig{Mode: PinInputAnalog})

 	resolution, samples := config.Resolution, config.Samples
 	if 0 == resolution {
@@ -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")
@@ -156,8 +165,8 @@ func (i2c *I2C) Configure(config I2CConfig) {
 	sda, scl := i2c.setPins(config)

 	// configure the mux and pad control registers
-	sda.Configure(PinConfig{Mode: pinModeI2CSDA})
-	scl.Configure(PinConfig{Mode: pinModeI2CSCL})
+	sda.Configure(PinConfig{Mode: PinModeI2CSDA})
+	scl.Configure(PinConfig{Mode: PinModeI2CSCL})

 	// configure the mux input selector
 	i2c.muxSDA.connect()
@@ -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)
@@ -77,10 +77,10 @@ func (spi *SPI) Configure(config SPIConfig) {
 	spi.sdi, spi.sdo, spi.sck, spi.cs = config.getPins()

 	// configure the mux and pad control registers
-	spi.sdi.Configure(PinConfig{Mode: pinModeSPISDI})
-	spi.sdo.Configure(PinConfig{Mode: pinModeSPISDO})
-	spi.sck.Configure(PinConfig{Mode: pinModeSPICLK})
-	spi.cs.Configure(PinConfig{Mode: pinModeSPICS})
+	spi.sdi.Configure(PinConfig{Mode: PinModeSPISDI})
+	spi.sdo.Configure(PinConfig{Mode: PinModeSPISDO})
+	spi.sck.Configure(PinConfig{Mode: PinModeSPICLK})
+	spi.cs.Configure(PinConfig{Mode: PinModeSPICS})

 	// configure the mux input selector
 	spi.muxSDI.connect()
@@ -68,8 +68,8 @@ func (uart *UART) Configure(config UARTConfig) {
 	uart.tx = config.TX

 	// configure the mux and pad control registers
-	uart.rx.Configure(PinConfig{Mode: pinModeUARTRX})
-	uart.tx.Configure(PinConfig{Mode: pinModeUARTTX})
+	uart.rx.Configure(PinConfig{Mode: PinModeUARTRX})
+	uart.tx.Configure(PinConfig{Mode: PinModeUARTTX})

 	// configure the mux input selector
 	uart.muxRX.connect()
@@ -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
 }
@@ -81,13 +81,11 @@ const (
 	PinInput
 	PinInputPulldown
 	PinInputPullup
-
-	// internal pin modes
-	pinAnalog
-	pinUART
-	pinPWM
-	pinI2C
-	pinSPI
+	PinAnalog
+	PinUART
+	PinPWM
+	PinI2C
+	PinSPI
 )

 func (p Pin) PortMaskSet() (*uint32, uint32) {
@@ -190,20 +188,20 @@ func (p Pin) Configure(config PinConfig) {
 	case PinInputPullup:
 		p.setFunc(fnSIO)
 		p.pullup()
-	case pinAnalog:
+	case PinAnalog:
 		p.setFunc(fnNULL)
 		p.pulloff()
-	case pinUART:
+	case PinUART:
 		p.setFunc(fnUART)
-	case pinPWM:
+	case PinPWM:
 		p.setFunc(fnPWM)
-	case pinI2C:
+	case PinI2C:
 		// IO config according to 4.3.1.3 of rp2040 datasheet.
 		p.setFunc(fnI2C)
 		p.pullup()
 		p.setSchmitt(true)
 		p.setSlew(false)
-	case pinSPI:
+	case PinSPI:
 		p.setFunc(fnSPI)
 	}
 }
@@ -228,8 +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
 )
@@ -105,8 +105,8 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	if config.Frequency == 0 {
 		config.Frequency = defaultBaud
 	}
-	config.SDA.Configure(PinConfig{pinI2C})
-	config.SCL.Configure(PinConfig{pinI2C})
+	config.SDA.Configure(PinConfig{PinI2C})
+	config.SCL.Configure(PinConfig{PinI2C})
 	return i2c.init(config)
 }

@@ -92,7 +92,7 @@ func (pwm *pwmGroup) Channel(pin Pin) (channel uint8, err error) {
 	if pin > maxPWMPins || pwmGPIOToSlice(pin) != pwm.peripheral() {
 		return 3, ErrInvalidOutputPin
 	}
-	pin.Configure(PinConfig{pinPWM})
+	pin.Configure(PinConfig{PinPWM})
 	return pwmGPIOToChannel(pin), nil
 }

@@ -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 {
@@ -42,8 +42,8 @@ func (uart *UART) Configure(config UARTConfig) error {
 		rp.UART0_UARTCR_TXE)

 	// set GPIO mux to UART for the pins
-	config.TX.Configure(PinConfig{Mode: pinUART})
-	config.RX.Configure(PinConfig{Mode: pinUART})
+	config.TX.Configure(PinConfig{Mode: PinUART})
+	config.RX.Configure(PinConfig{Mode: PinUART})

 	// Enable RX IRQ.
 	uart.Interrupt.SetPriority(0x80)
@@ -41,7 +41,7 @@ func InitADC() {

 // Configure configures an ADC pin to be able to read analog data.
 func (a ADC) Configure(ADCConfig) {
-	a.Pin.Configure(PinConfig{Mode: pinInputModeAnalog})
+	a.Pin.Configure(PinConfig{Mode: PinInputModeAnalog})

 	// set sample time
 	ch := a.getChannel()
@@ -36,7 +36,7 @@ func InitADC() {

 // Configure configures an ADC pin to be able to read analog data.
 func (a ADC) Configure(ADCConfig) {
-	a.Pin.ConfigureAltFunc(PinConfig{Mode: pinInputAnalog}, 0)
+	a.Pin.ConfigureAltFunc(PinConfig{Mode: PinInputAnalog}, 0)

 	// set sample time
 	ch := a.getChannel()
@@ -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
@@ -102,8 +102,8 @@ func (i2c *I2C) Tx(addr uint16, w, r []byte) error {
 }

 func (i2c *I2C) configurePins(config I2CConfig) {
-	config.SCL.ConfigureAltFunc(PinConfig{Mode: pinModeI2CSCL}, i2c.AltFuncSelector)
-	config.SDA.ConfigureAltFunc(PinConfig{Mode: pinModeI2CSDA}, i2c.AltFuncSelector)
+	config.SCL.ConfigureAltFunc(PinConfig{Mode: PinModeI2CSCL}, i2c.AltFuncSelector)
+	config.SDA.ConfigureAltFunc(PinConfig{Mode: PinModeI2CSDA}, i2c.AltFuncSelector)
 }

 func (i2c *I2C) controllerTransmit(addr uint16, w []byte) error {
@@ -14,28 +14,29 @@ import (
 const (
 	// Mode Flag
 	PinOutput        PinMode = 0
-	PinInput         PinMode = 1
+	PinInput         PinMode = PinInputFloating
+	PinInputFloating PinMode = 1
 	PinInputPulldown PinMode = 2
 	PinInputPullup   PinMode = 3

 	// for UART
-	pinModeUARTTX PinMode = 4
-	pinModeUARTRX PinMode = 5
+	PinModeUARTTX PinMode = 4
+	PinModeUARTRX PinMode = 5

 	// for I2C
-	pinModeI2CSCL PinMode = 6
-	pinModeI2CSDA PinMode = 7
+	PinModeI2CSCL PinMode = 6
+	PinModeI2CSDA PinMode = 7

 	// for SPI
-	pinModeSPICLK PinMode = 8
-	pinModeSPISDO PinMode = 9
-	pinModeSPISDI PinMode = 10
+	PinModeSPICLK PinMode = 8
+	PinModeSPISDO PinMode = 9
+	PinModeSPISDI PinMode = 10

 	// for analog/ADC
-	pinInputAnalog PinMode = 11
+	PinInputAnalog PinMode = 11

 	// for PWM
-	pinModePWMOutput PinMode = 12
+	PinModePWMOutput PinMode = 12
 )

 // Define several bitfields that have different names across chip families but
@@ -82,7 +83,7 @@ func (p Pin) ConfigureAltFunc(config PinConfig, altFunc uint8) {
 	switch config.Mode {

 	// GPIO
-	case PinInput:
+	case PinInputFloating:
 		port.MODER.ReplaceBits(gpioModeInput, gpioModeMask, pos)
 		port.PUPDR.ReplaceBits(gpioPullFloating, gpioPullMask, pos)
 	case PinInputPulldown:
@@ -96,24 +97,24 @@ func (p Pin) ConfigureAltFunc(config PinConfig, altFunc uint8) {
 		port.OSPEEDR.ReplaceBits(gpioOutputSpeedHigh, gpioOutputSpeedMask, pos)

 	// UART
-	case pinModeUARTTX:
+	case PinModeUARTTX:
 		port.MODER.ReplaceBits(gpioModeAlternate, gpioModeMask, pos)
 		port.OSPEEDR.ReplaceBits(gpioOutputSpeedHigh, gpioOutputSpeedMask, pos)
 		port.PUPDR.ReplaceBits(gpioPullUp, gpioPullMask, pos)
 		p.SetAltFunc(altFunc)
-	case pinModeUARTRX:
+	case PinModeUARTRX:
 		port.MODER.ReplaceBits(gpioModeAlternate, gpioModeMask, pos)
 		port.PUPDR.ReplaceBits(gpioPullFloating, gpioPullMask, pos)
 		p.SetAltFunc(altFunc)

 	// I2C
-	case pinModeI2CSCL:
+	case PinModeI2CSCL:
 		port.MODER.ReplaceBits(gpioModeAlternate, gpioModeMask, pos)
 		port.OTYPER.ReplaceBits(stm32.GPIO_OTYPER_OT0_OpenDrain, stm32.GPIO_OTYPER_OT0_Msk, pos/2)
 		port.OSPEEDR.ReplaceBits(gpioOutputSpeedLow, gpioOutputSpeedMask, pos)
 		port.PUPDR.ReplaceBits(gpioPullUp, gpioPullMask, pos)
 		p.SetAltFunc(altFunc)
-	case pinModeI2CSDA:
+	case PinModeI2CSDA:
 		port.MODER.ReplaceBits(gpioModeAlternate, gpioModeMask, pos)
 		port.OTYPER.ReplaceBits(stm32.GPIO_OTYPER_OT0_OpenDrain, stm32.GPIO_OTYPER_OT0_Msk, pos/2)
 		port.OSPEEDR.ReplaceBits(gpioOutputSpeedLow, gpioOutputSpeedMask, pos)
@@ -121,31 +122,31 @@ func (p Pin) ConfigureAltFunc(config PinConfig, altFunc uint8) {
 		p.SetAltFunc(altFunc)

 	// SPI
-	case pinModeSPICLK:
+	case PinModeSPICLK:
 		port.MODER.ReplaceBits(gpioModeAlternate, gpioModeMask, pos)
 		port.OSPEEDR.ReplaceBits(gpioOutputSpeedHigh, gpioOutputSpeedMask, pos)
 		port.PUPDR.ReplaceBits(gpioPullFloating, gpioPullMask, pos)
 		p.SetAltFunc(altFunc)
-	case pinModeSPISDO:
+	case PinModeSPISDO:
 		port.MODER.ReplaceBits(gpioModeAlternate, gpioModeMask, pos)
 		port.OSPEEDR.ReplaceBits(gpioOutputSpeedLow, gpioOutputSpeedMask, pos)
 		port.PUPDR.ReplaceBits(gpioPullFloating, gpioPullMask, pos)
 		p.SetAltFunc(altFunc)
-	case pinModeSPISDI:
+	case PinModeSPISDI:
 		port.MODER.ReplaceBits(gpioModeAlternate, gpioModeMask, pos)
 		port.OSPEEDR.ReplaceBits(gpioOutputSpeedLow, gpioOutputSpeedMask, pos)
 		port.PUPDR.ReplaceBits(gpioPullFloating, gpioPullMask, pos)
 		p.SetAltFunc(altFunc)

 	// PWM
-	case pinModePWMOutput:
+	case PinModePWMOutput:
 		port.MODER.ReplaceBits(gpioModeAlternate, gpioModeMask, pos)
 		port.OSPEEDR.ReplaceBits(gpioOutputSpeedHigh, gpioOutputSpeedMask, pos)
 		port.PUPDR.ReplaceBits(gpioPullFloating, gpioPullMask, pos)
 		p.SetAltFunc(altFunc)

 	// ADC
-	case pinInputAnalog:
+	case PinInputAnalog:
 		port.MODER.ReplaceBits(gpioModeAnalog, gpioModeMask, pos)
 	}
 }
@@ -183,7 +183,7 @@ func (t *TIM) Channel(pin Pin) (uint8, error) {
 		for _, p := range ch.Pins {
 			if p.Pin == pin {
 				t.configurePin(uint8(chi), p)
-				//p.Pin.ConfigureAltFunc(PinConfig{Mode: pinModePWMOutput}, p.AltFunc)
+				//p.Pin.ConfigureAltFunc(PinConfig{Mode: PinModePWMOutput}, p.AltFunc)
 				return uint8(chi), nil
 			}
 		}
@@ -7,5 +7,5 @@ package machine
 // register (most MCUs except STM32F1 series).

 func (t *TIM) configurePin(channel uint8, pf PinFunction) {
-	pf.Pin.ConfigureAltFunc(PinConfig{Mode: pinModePWMOutput}, pf.AltFunc)
+	pf.Pin.ConfigureAltFunc(PinConfig{Mode: PinModePWMOutput}, pf.AltFunc)
 }
@@ -29,20 +29,20 @@ const (
 	PinOutput50MHz PinMode = 3 // Output mode, max speed 50MHz
 	PinOutput      PinMode = PinOutput2MHz

-	pinInputModeAnalog     PinMode = 0  // Input analog mode
-	pinInputModeFloating   PinMode = 4  // Input floating mode
-	pinInputModePullUpDown PinMode = 8  // Input pull up/down mode
-	pinInputModeReserved   PinMode = 12 // Input mode (reserved)
+	PinInputModeAnalog     PinMode = 0  // Input analog mode
+	PinInputModeFloating   PinMode = 4  // Input floating mode
+	PinInputModePullUpDown PinMode = 8  // Input pull up/down mode
+	PinInputModeReserved   PinMode = 12 // Input mode (reserved)

-	pinOutputModeGPPushPull   PinMode = 0  // Output mode general purpose push/pull
-	pinOutputModeGPOpenDrain  PinMode = 4  // Output mode general purpose open drain
-	pinOutputModeAltPushPull  PinMode = 8  // Output mode alt. purpose push/pull
-	pinOutputModeAltOpenDrain PinMode = 12 // Output mode alt. purpose open drain
+	PinOutputModeGPPushPull   PinMode = 0  // Output mode general purpose push/pull
+	PinOutputModeGPOpenDrain  PinMode = 4  // Output mode general purpose open drain
+	PinOutputModeAltPushPull  PinMode = 8  // Output mode alt. purpose push/pull
+	PinOutputModeAltOpenDrain PinMode = 12 // Output mode alt. purpose open drain

 	// Pull-up vs Pull down is not part of the CNF0 / CNF1 bits, but is
 	// controlled by PxODR.  Encoded using the 'spare' bit 5.
-	PinInputPulldown PinMode = pinInputModePullUpDown
-	PinInputPullup   PinMode = pinInputModePullUpDown | 0x10
+	PinInputPulldown PinMode = PinInputModePullUpDown
+	PinInputPullup   PinMode = PinInputModePullUpDown | 0x10
 )

 // Pin constants for all stm32f103 package sizes
@@ -166,7 +166,7 @@ func (p Pin) Configure(config PinConfig) {

 	// If configured for input pull-up or pull-down, set ODR
 	// for desired pull-up or pull-down.
-	if (config.Mode & 0xf) == pinInputModePullUpDown {
+	if (config.Mode & 0xf) == PinInputModePullUpDown {
 		var pullup uint32
 		if config.Mode == PinInputPullup {
 			pullup = 1
@@ -290,8 +290,8 @@ func (uart *UART) configurePins(config UARTConfig) {
 	default:
 		// use standard TX/RX pins PA9 and PA10
 	}
-	config.TX.Configure(PinConfig{Mode: PinOutput50MHz + pinOutputModeAltPushPull})
-	config.RX.Configure(PinConfig{Mode: pinInputModeFloating})
+	config.TX.Configure(PinConfig{Mode: PinOutput50MHz + PinOutputModeAltPushPull})
+	config.RX.Configure(PinConfig{Mode: PinInputModeFloating})
 }

 // Determine the divisor for USARTs to get the given baudrate
@@ -363,9 +363,9 @@ func (spi SPI) getBaudRate(config SPIConfig) uint32 {

 // Configure SPI pins for input output and clock
 func (spi SPI) configurePins(config SPIConfig) {
-	config.SCK.Configure(PinConfig{Mode: PinOutput50MHz + pinOutputModeAltPushPull})
-	config.SDO.Configure(PinConfig{Mode: PinOutput50MHz + pinOutputModeAltPushPull})
-	config.SDI.Configure(PinConfig{Mode: pinInputModeFloating})
+	config.SCK.Configure(PinConfig{Mode: PinOutput50MHz + PinOutputModeAltPushPull})
+	config.SDO.Configure(PinConfig{Mode: PinOutput50MHz + PinOutputModeAltPushPull})
+	config.SDI.Configure(PinConfig{Mode: PinInputModeFloating})
 }

 //---------- I2C related types and code
@@ -390,8 +390,8 @@ func (i2c *I2C) configurePins(config I2CConfig) {
 		stm32.AFIO.MAPR.SetBits(stm32.AFIO_MAPR_I2C1_REMAP)
 	}

-	config.SDA.Configure(PinConfig{Mode: PinOutput50MHz + pinOutputModeAltOpenDrain})
-	config.SCL.Configure(PinConfig{Mode: PinOutput50MHz + pinOutputModeAltOpenDrain})
+	config.SDA.Configure(PinConfig{Mode: PinOutput50MHz + PinOutputModeAltOpenDrain})
+	config.SCL.Configure(PinConfig{Mode: PinOutput50MHz + PinOutputModeAltOpenDrain})
 }

 func (i2c *I2C) getFreqRange(config I2CConfig) uint32 {
@@ -717,7 +717,7 @@ func (t *TIM) configurePin(channel uint8, pf PinFunction) {
 		stm32.AFIO.MAPR.ReplaceBits(remap<<stm32.AFIO_MAPR2_TIM14_REMAP_Pos, stm32.AFIO_MAPR2_TIM14_REMAP_Msk, 0)
 	}

-	pf.Pin.Configure(PinConfig{Mode: PinOutput + pinOutputModeAltPushPull})
+	pf.Pin.Configure(PinConfig{Mode: PinOutput + PinOutputModeAltPushPull})
 }

 func (t *TIM) enableMainOutput() {
@@ -640,8 +640,8 @@ const (

 func (uart *UART) configurePins(config UARTConfig) {
 	// enable the alternate functions on the TX and RX pins
-	config.TX.ConfigureAltFunc(PinConfig{Mode: pinModeUARTTX}, uart.TxAltFuncSelector)
-	config.RX.ConfigureAltFunc(PinConfig{Mode: pinModeUARTRX}, uart.RxAltFuncSelector)
+	config.TX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTTX}, uart.TxAltFuncSelector)
+	config.RX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTRX}, uart.RxAltFuncSelector)
 }

 func (uart *UART) getBaudRateDivisor(baudRate uint32) uint32 {
@@ -674,9 +674,9 @@ func (spi SPI) config8Bits() {
 }

 func (spi SPI) configurePins(config SPIConfig) {
-	config.SCK.ConfigureAltFunc(PinConfig{Mode: pinModeSPICLK}, spi.AltFuncSelector)
-	config.SDO.ConfigureAltFunc(PinConfig{Mode: pinModeSPISDO}, spi.AltFuncSelector)
-	config.SDI.ConfigureAltFunc(PinConfig{Mode: pinModeSPISDI}, spi.AltFuncSelector)
+	config.SCK.ConfigureAltFunc(PinConfig{Mode: PinModeSPICLK}, spi.AltFuncSelector)
+	config.SDO.ConfigureAltFunc(PinConfig{Mode: PinModeSPISDO}, spi.AltFuncSelector)
+	config.SDI.ConfigureAltFunc(PinConfig{Mode: PinModeSPISDI}, spi.AltFuncSelector)
 }

 func (spi SPI) getBaudRate(config SPIConfig) uint32 {
@@ -723,8 +723,8 @@ type I2C struct {
 }

 func (i2c *I2C) configurePins(config I2CConfig) {
-	config.SCL.ConfigureAltFunc(PinConfig{Mode: pinModeI2CSCL}, i2c.AltFuncSelector)
-	config.SDA.ConfigureAltFunc(PinConfig{Mode: pinModeI2CSDA}, i2c.AltFuncSelector)
+	config.SCL.ConfigureAltFunc(PinConfig{Mode: PinModeI2CSCL}, i2c.AltFuncSelector)
+	config.SDA.ConfigureAltFunc(PinConfig{Mode: PinModeI2CSDA}, i2c.AltFuncSelector)
 }

 func (i2c *I2C) getFreqRange(config I2CConfig) uint32 {
@@ -24,8 +24,8 @@ const APB2_TIM_FREQ = 216e6 // 216MHz
 // Configure the UART.
 func (uart *UART) configurePins(config UARTConfig) {
 	// enable the alternate functions on the TX and RX pins
-	config.TX.ConfigureAltFunc(PinConfig{Mode: pinModeUARTTX}, uart.TxAltFuncSelector)
-	config.RX.ConfigureAltFunc(PinConfig{Mode: pinModeUARTRX}, uart.RxAltFuncSelector)
+	config.TX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTTX}, uart.TxAltFuncSelector)
+	config.RX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTRX}, uart.RxAltFuncSelector)
 }

 // UART baudrate calc based on the bus and clockspeed
@@ -195,8 +195,8 @@ func (p Pin) registerInterrupt() interrupt.Interrupt {
 // Configure the UART.
 func (uart *UART) configurePins(config UARTConfig) {
 	// enable the alternate functions on the TX and RX pins
-	config.TX.ConfigureAltFunc(PinConfig{Mode: pinModeUARTTX}, uart.TxAltFuncSelector)
-	config.RX.ConfigureAltFunc(PinConfig{Mode: pinModeUARTRX}, uart.RxAltFuncSelector)
+	config.TX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTTX}, uart.TxAltFuncSelector)
+	config.RX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTRX}, uart.RxAltFuncSelector)
 }

 // UART baudrate calc based on the bus and clockspeed
@@ -289,9 +289,9 @@ func (spi SPI) getBaudRate(config SPIConfig) uint32 {

 // Configure SPI pins for input output and clock
 func (spi SPI) configurePins(config SPIConfig) {
-	config.SCK.ConfigureAltFunc(PinConfig{Mode: pinModeSPICLK}, spi.AltFuncSelector)
-	config.SDO.ConfigureAltFunc(PinConfig{Mode: pinModeSPISDO}, spi.AltFuncSelector)
-	config.SDI.ConfigureAltFunc(PinConfig{Mode: pinModeSPISDI}, spi.AltFuncSelector)
+	config.SCK.ConfigureAltFunc(PinConfig{Mode: PinModeSPICLK}, spi.AltFuncSelector)
+	config.SDO.ConfigureAltFunc(PinConfig{Mode: PinModeSPISDO}, spi.AltFuncSelector)
+	config.SDI.ConfigureAltFunc(PinConfig{Mode: PinModeSPISDI}, spi.AltFuncSelector)
 }

 //---------- I2C related types and code
@@ -280,8 +280,8 @@ func (p Pin) registerInterrupt() interrupt.Interrupt {
 // Configure the UART.
 func (uart *UART) configurePins(config UARTConfig) {
 	// enable the alternate functions on the TX and RX pins
-	config.TX.ConfigureAltFunc(PinConfig{Mode: pinModeUARTTX}, uart.TxAltFuncSelector)
-	config.RX.ConfigureAltFunc(PinConfig{Mode: pinModeUARTRX}, uart.RxAltFuncSelector)
+	config.TX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTTX}, uart.TxAltFuncSelector)
+	config.RX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTRX}, uart.RxAltFuncSelector)
 }

 // UART baudrate calc based on the bus and clockspeed
@@ -357,9 +357,9 @@ func (spi SPI) getBaudRate(config SPIConfig) uint32 {

 // Configure SPI pins for input output and clock
 func (spi SPI) configurePins(config SPIConfig) {
-	config.SCK.ConfigureAltFunc(PinConfig{Mode: pinModeSPICLK}, spi.AltFuncSelector)
-	config.SDO.ConfigureAltFunc(PinConfig{Mode: pinModeSPISDO}, spi.AltFuncSelector)
-	config.SDI.ConfigureAltFunc(PinConfig{Mode: pinModeSPISDI}, spi.AltFuncSelector)
+	config.SCK.ConfigureAltFunc(PinConfig{Mode: PinModeSPICLK}, spi.AltFuncSelector)
+	config.SDO.ConfigureAltFunc(PinConfig{Mode: PinModeSPISDO}, spi.AltFuncSelector)
+	config.SDI.ConfigureAltFunc(PinConfig{Mode: PinModeSPISDI}, spi.AltFuncSelector)
 }

 //---------- Timer related code
@@ -29,8 +29,8 @@ func (uart *UART) configurePins(config UARTConfig) {
 	}

 	// enable the alternate functions on the TX and RX pins
-	config.TX.ConfigureAltFunc(PinConfig{Mode: pinModeUARTTX}, uart.TxAltFuncSelector)
-	config.RX.ConfigureAltFunc(PinConfig{Mode: pinModeUARTRX}, uart.RxAltFuncSelector)
+	config.TX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTTX}, uart.TxAltFuncSelector)
+	config.RX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTRX}, uart.RxAltFuncSelector)
 }

 // UART baudrate calc based on the bus and clockspeed
@@ -239,9 +239,9 @@ func (spi SPI) config8Bits() {
 }

 func (spi SPI) configurePins(config SPIConfig) {
-	config.SCK.ConfigureAltFunc(PinConfig{Mode: pinModeSPICLK}, spi.AltFuncSelector)
-	config.SDO.ConfigureAltFunc(PinConfig{Mode: pinModeSPISDO}, spi.AltFuncSelector)
-	config.SDI.ConfigureAltFunc(PinConfig{Mode: pinModeSPISDI}, spi.AltFuncSelector)
+	config.SCK.ConfigureAltFunc(PinConfig{Mode: PinModeSPICLK}, spi.AltFuncSelector)
+	config.SDO.ConfigureAltFunc(PinConfig{Mode: PinModeSPISDO}, spi.AltFuncSelector)
+	config.SDI.ConfigureAltFunc(PinConfig{Mode: PinModeSPISDI}, spi.AltFuncSelector)
 }

 func (spi SPI) getBaudRate(config SPIConfig) uint32 {
@@ -298,8 +298,8 @@ func (i2c *I2C) getFreqRange() uint32 {
 // Configure the UART.
 func (uart UART) configurePins(config UARTConfig) {
 	// enable the alternate functions on the TX and RX pins
-	config.TX.ConfigureAltFunc(PinConfig{Mode: pinModeUARTTX}, uart.TxAltFuncSelector)
-	config.RX.ConfigureAltFunc(PinConfig{Mode: pinModeUARTRX}, uart.RxAltFuncSelector)
+	config.TX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTTX}, uart.TxAltFuncSelector)
+	config.RX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTRX}, uart.RxAltFuncSelector)
 }

 // UART baudrate calc based on the bus and clockspeed
@@ -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
@@ -73,14 +48,14 @@ 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
@@ -93,6 +68,7 @@ func growHeap() bool {
 var allocs = make(map[uintptr][]byte)

 //export malloc
+//go:wasm-module
 func libc_malloc(size uintptr) unsafe.Pointer {
 	buf := make([]byte, size)
 	ptr := unsafe.Pointer(&buf[0])
@@ -101,6 +77,7 @@ func libc_malloc(size uintptr) unsafe.Pointer {
 }

 //export free
+//go:wasm-module
 func libc_free(ptr unsafe.Pointer) {
 	if ptr == nil {
 		return
@@ -113,12 +90,14 @@ func libc_free(ptr unsafe.Pointer) {
 }

 //export calloc
+//go:wasm-module
 func libc_calloc(nmemb, size uintptr) unsafe.Pointer {
 	// No difference between calloc and malloc.
 	return libc_malloc(nmemb * size)
 }

 //export realloc
+//go:wasm-module
 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.
--- a/Show More
+++ b/Show More