gdew0154m09: add e-paper display driver

examples/gdew0154m09/main.go

@@ -0,0 +1,69 @@
+package main
+
+import (
+	"device/esp"
+	"image/color"
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers/gdew0154m09"
+	"tinygo.org/x/tinyfont"
+	"tinygo.org/x/tinyfont/freemono"
+)
+
+func main() {
+	// Hold the M5Stack CoreInk power rail on.
+	machine.GPIO12.Configure(machine.PinConfig{Mode: machine.PinOutput})
+	machine.GPIO12.High()
+
+	cs := machine.IO9
+	dc := machine.GPIO15
+	rst := machine.IO0
+	busy := machine.IO4
+	cs.Configure(machine.PinConfig{Mode: machine.PinOutput})
+	dc.Configure(machine.PinConfig{Mode: machine.PinOutput})
+	rst.Configure(machine.PinConfig{Mode: machine.PinOutput})
+	busy.Configure(machine.PinConfig{Mode: machine.PinInput})
+	cs.High()
+	dc.High()
+	rst.High()
+
+	// Enable and reset the ESP32 VSPI peripheral before configuring SPI3.
+	esp.DPORT.SetPERIP_RST_EN_SPI3_RST(1)
+	esp.DPORT.SetPERIP_CLK_EN_SPI3_CLK_EN(1)
+	esp.DPORT.SetPERIP_RST_EN_SPI3_RST(0)
+	if err := machine.SPI3.Configure(machine.SPIConfig{
+		Frequency: gdew0154m09.Baudrate,
+		SCK:       machine.IO18,
+		SDO:       machine.IO23,
+		SDI:       machine.NoPin,
+		Mode:      gdew0154m09.SPIMode,
+	}); err != nil {
+		println("could not configure SPI:", err.Error())
+		return
+	}
+
+	display := gdew0154m09.New(machine.SPI3, cs, dc, rst, busy)
+	if err := display.Configure(gdew0154m09.DefaultConfig); err != nil {
+		println("could not configure display:", err.Error())
+		return
+	}
+
+	black := color.RGBA{A: 0xff}
+	tinyfont.WriteLine(display, &freemono.Bold18pt7b, 15, 90, "TinyGo", black)
+	for x := int16(0); x < gdew0154m09.Width; x++ {
+		display.SetPixel(x, 0, black)
+		display.SetPixel(x, gdew0154m09.Height-1, black)
+	}
+	for y := int16(0); y < gdew0154m09.Height; y++ {
+		display.SetPixel(0, y, black)
+		display.SetPixel(gdew0154m09.Width-1, y, black)
+	}
+
+	if err := display.Display(); err != nil {
+		println("could not refresh display:", err.Error())
+	}
+	for {
+		time.Sleep(time.Hour)
+	}
+}

gdew0154m09/gdew0154m09.go

@@ -0,0 +1,297 @@
+// Package gdew0154m09 provides a driver for the Good Display GDEW0154M09
+// 1.54-inch 200x200 monochrome e-paper panel used by the M5Stack CoreInk.
+//
+// The initialization sequence is based on the MIT-licensed M5Stack
+// M5Core-Ink library:
+// https://github.com/m5stack/M5Core-Ink
+package gdew0154m09 // import "tinygo.org/x/drivers/gdew0154m09"
+
+import (
+	"errors"
+	"image/color"
+	"time"
+
+	"tinygo.org/x/drivers"
+)
+
+const (
+	// Width and Height are the physical panel dimensions in pixels.
+	Width  = 200
+	Height = 200
+
+	// Baudrate and SPIMode are the recommended SPI bus configuration.
+	Baudrate = 10_000_000
+	SPIMode  = 3
+
+	frameBufferSize = Width * Height / 8
+)
+
+var (
+	ErrBusyTimeout        = errors.New("gdew0154m09: busy timeout")
+	ErrInvalidBusyTimeout = errors.New("gdew0154m09: busy timeout must not be negative")
+)
+
+// OutputPin is the interface required from an output pin. Pins must be
+// configured by the caller before they are passed to New.
+type OutputPin interface {
+	Set(level bool)
+}
+
+// InputPin is the interface required from an input pin. The pin must be
+// configured by the caller before it is passed to New.
+type InputPin interface {
+	Get() bool
+}
+
+// Config contains the display configuration.
+type Config struct {
+	// BusyTimeout is the maximum time to wait for a panel operation. A zero
+	// duration selects the default timeout.
+	BusyTimeout time.Duration
+}
+
+// DefaultConfig contains the recommended display configuration.
+var DefaultConfig = Config{
+	BusyTimeout: 5 * time.Second,
+}
+
+// Device is a GDEW0154M09 display connected over SPI.
+type Device struct {
+	bus  drivers.SPI
+	cs   OutputPin
+	dc   OutputPin
+	rst  OutputPin
+	busy InputPin
+
+	buffer      [frameBufferSize]byte
+	previous    [frameBufferSize]byte
+	tx          [3]byte
+	busyTimeout time.Duration
+}
+
+var _ drivers.Displayer = (*Device)(nil)
+
+// New returns a new GDEW0154M09 driver. The SPI bus and pins must already be
+// configured. New performs no I/O.
+func New(bus drivers.SPI, cs, dc, rst OutputPin, busy InputPin) *Device {
+	d := &Device{
+		bus:         bus,
+		cs:          cs,
+		dc:          dc,
+		rst:         rst,
+		busy:        busy,
+		busyTimeout: DefaultConfig.BusyTimeout,
+	}
+	d.ClearBuffer()
+	fill(d.previous[:], 0xff)
+	return d
+}
+
+// Configure resets and initializes the display controller. It also clears the
+// current and previous framebuffers to white without refreshing the panel.
+func (d *Device) Configure(config Config) error {
+	if config.BusyTimeout < 0 {
+		return ErrInvalidBusyTimeout
+	}
+	if config.BusyTimeout == 0 {
+		config.BusyTimeout = DefaultConfig.BusyTimeout
+	}
+	d.busyTimeout = config.BusyTimeout
+
+	d.hardwareReset()
+	if err := d.waitUntilIdle(); err != nil {
+		return err
+	}
+
+	if err := d.sendCommand2(commandPanelSetting, 0xdf, 0x0e); err != nil {
+		return err
+	}
+	if err := d.sendCommand1(commandFITIInternalCode, 0x55); err != nil {
+		return err
+	}
+	if err := d.sendCommand1(commandUnknownAA, 0x0f); err != nil {
+		return err
+	}
+	if err := d.sendCommand1(commandUnknownE9, 0x02); err != nil {
+		return err
+	}
+	if err := d.sendCommand1(commandBoosterSoftStart, 0x11); err != nil {
+		return err
+	}
+	if err := d.sendCommand1(commandPowerSequence, 0x0a); err != nil {
+		return err
+	}
+	if err := d.sendCommand3(commandResolutionSetting, 0xc8, 0x00, 0xc8); err != nil {
+		return err
+	}
+	if err := d.sendCommand1(commandTCONSetting, 0x00); err != nil {
+		return err
+	}
+	if err := d.sendCommand1(commandVCOMDataInterval, defaultVCOMDataInterval); err != nil {
+		return err
+	}
+	if err := d.sendCommand1(commandPowerSaving, 0x00); err != nil {
+		return err
+	}
+	if err := d.sendCommand(commandPowerOn); err != nil {
+		return err
+	}
+
+	time.Sleep(100 * time.Millisecond)
+	if err := d.waitUntilIdle(); err != nil {
+		return err
+	}
+	d.ClearBuffer()
+	fill(d.previous[:], 0xff)
+	return nil
+}
+
+// Size returns the dimensions of the display in pixels.
+func (d *Device) Size() (width, height int16) {
+	return Width, Height
+}
+
+// SetPixel updates one pixel in the framebuffer. Transparent and light colors
+// are rendered white; opaque dark colors are rendered black.
+func (d *Device) SetPixel(x, y int16, c color.RGBA) {
+	if x < 0 || x >= Width || y < 0 || y >= Height {
+		return
+	}
+	index := int(y)*(Width/8) + int(x)/8
+	mask := byte(0x80 >> uint(x%8))
+	brightness := uint16(c.R) + uint16(c.G) + uint16(c.B)
+	if c.A == 0 || brightness >= 3*128 {
+		d.buffer[index] |= mask
+	} else {
+		d.buffer[index] &^= mask
+	}
+}
+
+// ClearBuffer sets every pixel in the framebuffer to white without refreshing
+// the panel.
+func (d *Device) ClearBuffer() {
+	fill(d.buffer[:], 0xff)
+}
+
+// Display sends the previous and current framebuffers to the panel and starts
+// a full refresh. It blocks until the refresh completes or the busy timeout is
+// reached.
+func (d *Device) Display() error {
+	if err := d.sendCommand(commandDataStartOld); err != nil {
+		return err
+	}
+	if err := d.sendData(d.previous[:]); err != nil {
+		return err
+	}
+	time.Sleep(2 * time.Millisecond)
+
+	if err := d.sendCommand(commandDataStartNew); err != nil {
+		return err
+	}
+	if err := d.sendData(d.buffer[:]); err != nil {
+		return err
+	}
+	time.Sleep(2 * time.Millisecond)
+
+	if err := d.sendCommand(commandDisplayRefresh); err != nil {
+		return err
+	}
+	if err := d.waitUntilIdle(); err != nil {
+		return err
+	}
+	copy(d.previous[:], d.buffer[:])
+	return nil
+}
+
+// ClearDisplay clears the framebuffer and refreshes the panel.
+func (d *Device) ClearDisplay() error {
+	d.ClearBuffer()
+	return d.Display()
+}
+
+// DeepSleep powers off the panel and enters deep sleep. Configure must be
+// called to wake and reinitialize the controller.
+func (d *Device) DeepSleep() error {
+	if err := d.sendCommand1(commandVCOMDataInterval, deepSleepVCOMDataInterval); err != nil {
+		return err
+	}
+	if err := d.waitUntilIdle(); err != nil {
+		return err
+	}
+	if err := d.sendCommand(commandPowerOff); err != nil {
+		return err
+	}
+	return d.sendCommand1(commandDeepSleep, deepSleepCheckCode)
+}
+
+// IsBusy reports whether the active-low busy signal is asserted.
+func (d *Device) IsBusy() bool {
+	return !d.busy.Get()
+}
+
+func (d *Device) hardwareReset() {
+	d.rst.Set(true)
+	time.Sleep(10 * time.Millisecond)
+	d.rst.Set(false)
+	time.Sleep(100 * time.Millisecond)
+	d.rst.Set(true)
+	time.Sleep(100 * time.Millisecond)
+}
+
+func (d *Device) waitUntilIdle() error {
+	deadline := time.Now().Add(d.busyTimeout)
+	for d.IsBusy() {
+		if time.Now().After(deadline) {
+			return ErrBusyTimeout
+		}
+		time.Sleep(time.Millisecond)
+	}
+	return nil
+}
+
+func (d *Device) sendCommandWithData(command byte, data []byte) error {
+	if err := d.sendCommand(command); err != nil {
+		return err
+	}
+	return d.sendData(data)
+}
+
+func (d *Device) sendCommand1(command, data byte) error {
+	d.tx[0] = data
+	return d.sendCommandWithData(command, d.tx[:1])
+}
+
+func (d *Device) sendCommand2(command, data0, data1 byte) error {
+	d.tx[0] = data0
+	d.tx[1] = data1
+	return d.sendCommandWithData(command, d.tx[:2])
+}
+
+func (d *Device) sendCommand3(command, data0, data1, data2 byte) error {
+	d.tx[0] = data0
+	d.tx[1] = data1
+	d.tx[2] = data2
+	return d.sendCommandWithData(command, d.tx[:3])
+}
+
+func (d *Device) sendCommand(command byte) error {
+	d.dc.Set(false)
+	d.cs.Set(false)
+	_, err := d.bus.Transfer(command)
+	d.cs.Set(true)
+	return err
+}
+
+func (d *Device) sendData(data []byte) error {
+	d.dc.Set(true)
+	d.cs.Set(false)
+	err := d.bus.Tx(data, nil)
+	d.cs.Set(true)
+	return err
+}
+
+func fill(buffer []byte, value byte) {
+	for index := range buffer {
+		buffer[index] = value
+	}
+}

gdew0154m09/gdew0154m09_test.go

@@ -0,0 +1,313 @@
+package gdew0154m09
+
+import (
+	"bytes"
+	"errors"
+	"image/color"
+	"testing"
+	"time"
+)
+
+type fakeOutputPin struct {
+	high    bool
+	changes []bool
+}
+
+func (p *fakeOutputPin) Set(level bool) {
+	p.high = level
+	p.changes = append(p.changes, level)
+}
+
+type fakeInputPin struct {
+	high bool
+}
+
+func (p *fakeInputPin) Get() bool {
+	return p.high
+}
+
+type spiOperation struct {
+	command bool
+	data    []byte
+}
+
+type fakeSPI struct {
+	t          *testing.T
+	cs         *fakeOutputPin
+	dc         *fakeOutputPin
+	operations []spiOperation
+	failAt     int
+	failErr    error
+}
+
+func (s *fakeSPI) Transfer(value byte) (byte, error) {
+	s.t.Helper()
+	if s.cs.high {
+		s.t.Error("chip select was high during command transfer")
+	}
+	if s.dc.high {
+		s.t.Error("data/command pin was high during command transfer")
+	}
+	s.operations = append(s.operations, spiOperation{command: true, data: []byte{value}})
+	if len(s.operations) == s.failAt {
+		return 0, s.failErr
+	}
+	return 0, nil
+}
+
+func (s *fakeSPI) Tx(write, read []byte) error {
+	s.t.Helper()
+	if s.cs.high {
+		s.t.Error("chip select was high during data transfer")
+	}
+	if !s.dc.high {
+		s.t.Error("data/command pin was low during data transfer")
+	}
+	data := append([]byte(nil), write...)
+	s.operations = append(s.operations, spiOperation{data: data})
+	if len(s.operations) == s.failAt {
+		return s.failErr
+	}
+	return nil
+}
+
+func newTestDevice(t *testing.T) (*Device, *fakeSPI, *fakeOutputPin, *fakeInputPin) {
+	t.Helper()
+	cs := &fakeOutputPin{high: true}
+	dc := &fakeOutputPin{high: true}
+	rst := &fakeOutputPin{high: true}
+	busy := &fakeInputPin{high: true}
+	bus := &fakeSPI{t: t, cs: cs, dc: dc}
+	return New(bus, cs, dc, rst, busy), bus, rst, busy
+}
+
+func TestNewStartsWithWhiteBuffers(t *testing.T) {
+	device, _, _, _ := newTestDevice(t)
+	for index := range device.buffer {
+		if device.buffer[index] != 0xff || device.previous[index] != 0xff {
+			t.Fatalf("pixel byte %d was not initialized white", index)
+		}
+	}
+}
+
+func TestSize(t *testing.T) {
+	device, _, _, _ := newTestDevice(t)
+	width, height := device.Size()
+	if width != Width || height != Height {
+		t.Fatalf("size = %dx%d, want %dx%d", width, height, Width, Height)
+	}
+}
+
+func TestSetPixel(t *testing.T) {
+	device, _, _, _ := newTestDevice(t)
+	black := color.RGBA{A: 0xff}
+	white := color.RGBA{R: 0xff, G: 0xff, B: 0xff, A: 0xff}
+
+	device.SetPixel(0, 0, black)
+	device.SetPixel(199, 199, black)
+	if device.buffer[0] != 0x7f {
+		t.Fatalf("first byte = %#x, want 0x7f", device.buffer[0])
+	}
+	if device.buffer[len(device.buffer)-1] != 0xfe {
+		t.Fatalf("last byte = %#x, want 0xfe", device.buffer[len(device.buffer)-1])
+	}
+
+	device.SetPixel(0, 0, white)
+	if device.buffer[0] != 0xff {
+		t.Fatalf("first byte after white pixel = %#x, want 0xff", device.buffer[0])
+	}
+}
+
+func TestSetPixelIgnoresOutOfBoundsCoordinates(t *testing.T) {
+	device, _, _, _ := newTestDevice(t)
+	device.SetPixel(-1, 0, color.RGBA{A: 0xff})
+	device.SetPixel(0, -1, color.RGBA{A: 0xff})
+	device.SetPixel(Width, 0, color.RGBA{A: 0xff})
+	device.SetPixel(0, Height, color.RGBA{A: 0xff})
+	for index, value := range device.buffer {
+		if value != 0xff {
+			t.Fatalf("byte %d changed to %#x", index, value)
+		}
+	}
+}
+
+func TestConfigure(t *testing.T) {
+	device, bus, rst, _ := newTestDevice(t)
+	if err := device.Configure(Config{}); err != nil {
+		t.Fatal(err)
+	}
+	if device.busyTimeout != DefaultConfig.BusyTimeout {
+		t.Fatalf("busy timeout = %v, want %v", device.busyTimeout, DefaultConfig.BusyTimeout)
+	}
+
+	wantReset := []bool{true, false, true}
+	if !equalBools(rst.changes, wantReset) {
+		t.Fatalf("reset changes = %v, want %v", rst.changes, wantReset)
+	}
+	wantCommands := []byte{0x00, 0x4d, 0xaa, 0xe9, 0xb6, 0xf3, 0x61, 0x60, 0x50, 0xe3, 0x04}
+	if got := commandBytes(bus.operations); !bytes.Equal(got, wantCommands) {
+		t.Fatalf("commands = %#v, want %#v", got, wantCommands)
+	}
+
+	wantData := [][]byte{
+		{0xdf, 0x0e}, {0x55}, {0x0f}, {0x02}, {0x11}, {0x0a},
+		{0xc8, 0x00, 0xc8}, {0x00}, {0xd7}, {0x00},
+	}
+	if got := dataTransfers(bus.operations); !equalByteSlices(got, wantData) {
+		t.Fatalf("data transfers = %#v, want %#v", got, wantData)
+	}
+}
+
+func TestConfigurePropagatesSPIErrors(t *testing.T) {
+	wantErr := errors.New("SPI failure")
+	for _, operation := range []int{1, 2} {
+		t.Run(operationName(operation), func(t *testing.T) {
+			device, bus, _, _ := newTestDevice(t)
+			bus.failAt = operation
+			bus.failErr = wantErr
+			if err := device.Configure(DefaultConfig); !errors.Is(err, wantErr) {
+				t.Fatalf("error = %v, want %v", err, wantErr)
+			}
+			if !bus.cs.high {
+				t.Error("chip select was not released after SPI error")
+			}
+		})
+	}
+}
+
+func TestConfigureRejectsNegativeTimeout(t *testing.T) {
+	device, bus, rst, _ := newTestDevice(t)
+	err := device.Configure(Config{BusyTimeout: -time.Millisecond})
+	if !errors.Is(err, ErrInvalidBusyTimeout) {
+		t.Fatalf("error = %v, want %v", err, ErrInvalidBusyTimeout)
+	}
+	if len(bus.operations) != 0 || len(rst.changes) != 0 {
+		t.Fatal("invalid configuration performed hardware I/O")
+	}
+}
+
+func TestDisplaySendsOldAndNewFrames(t *testing.T) {
+	device, bus, _, _ := newTestDevice(t)
+	device.SetPixel(0, 0, color.RGBA{A: 0xff})
+	if err := device.Display(); err != nil {
+		t.Fatal(err)
+	}
+
+	if len(bus.operations) != 5 {
+		t.Fatalf("operation count = %d, want 5", len(bus.operations))
+	}
+	assertCommand(t, bus.operations[0], commandDataStartOld)
+	if len(bus.operations[1].data) != frameBufferSize || bus.operations[1].data[0] != 0xff {
+		t.Fatal("old frame was not initially white")
+	}
+	assertCommand(t, bus.operations[2], commandDataStartNew)
+	if len(bus.operations[3].data) != frameBufferSize || bus.operations[3].data[0] != 0x7f {
+		t.Fatal("new frame did not contain the black pixel")
+	}
+	assertCommand(t, bus.operations[4], commandDisplayRefresh)
+
+	bus.operations = nil
+	device.SetPixel(0, 0, color.RGBA{R: 0xff, G: 0xff, B: 0xff, A: 0xff})
+	if err := device.Display(); err != nil {
+		t.Fatal(err)
+	}
+	if bus.operations[1].data[0] != 0x7f {
+		t.Fatal("second refresh did not send the first frame as old data")
+	}
+}
+
+func TestDisplayPropagatesSPIErrors(t *testing.T) {
+	wantErr := errors.New("SPI failure")
+	for operation := 1; operation <= 5; operation++ {
+		t.Run(operationName(operation), func(t *testing.T) {
+			device, bus, _, _ := newTestDevice(t)
+			bus.failAt = operation
+			bus.failErr = wantErr
+			if err := device.Display(); !errors.Is(err, wantErr) {
+				t.Fatalf("error = %v, want %v", err, wantErr)
+			}
+			if !bus.cs.high {
+				t.Error("chip select was not released after SPI error")
+			}
+		})
+	}
+}
+
+func TestBusyTimeout(t *testing.T) {
+	device, _, _, busy := newTestDevice(t)
+	busy.high = false
+	device.busyTimeout = time.Millisecond
+	if err := device.waitUntilIdle(); !errors.Is(err, ErrBusyTimeout) {
+		t.Fatalf("error = %v, want %v", err, ErrBusyTimeout)
+	}
+}
+
+func TestDeepSleep(t *testing.T) {
+	device, bus, _, _ := newTestDevice(t)
+	if err := device.DeepSleep(); err != nil {
+		t.Fatal(err)
+	}
+	wantCommands := []byte{commandVCOMDataInterval, commandPowerOff, commandDeepSleep}
+	if got := commandBytes(bus.operations); !bytes.Equal(got, wantCommands) {
+		t.Fatalf("commands = %#v, want %#v", got, wantCommands)
+	}
+	wantData := [][]byte{{deepSleepVCOMDataInterval}, {deepSleepCheckCode}}
+	if got := dataTransfers(bus.operations); !equalByteSlices(got, wantData) {
+		t.Fatalf("data transfers = %#v, want %#v", got, wantData)
+	}
+}
+
+func assertCommand(t *testing.T, operation spiOperation, command byte) {
+	t.Helper()
+	if !operation.command || len(operation.data) != 1 || operation.data[0] != command {
+		t.Fatalf("operation = %#v, want command %#x", operation, command)
+	}
+}
+
+func commandBytes(operations []spiOperation) []byte {
+	var commands []byte
+	for _, operation := range operations {
+		if operation.command {
+			commands = append(commands, operation.data[0])
+		}
+	}
+	return commands
+}
+
+func dataTransfers(operations []spiOperation) [][]byte {
+	var transfers [][]byte
+	for _, operation := range operations {
+		if !operation.command {
+			transfers = append(transfers, operation.data)
+		}
+	}
+	return transfers
+}
+
+func equalBools(left, right []bool) bool {
+	if len(left) != len(right) {
+		return false
+	}
+	for index := range left {
+		if left[index] != right[index] {
+			return false
+		}
+	}
+	return true
+}
+
+func equalByteSlices(left, right [][]byte) bool {
+	if len(left) != len(right) {
+		return false
+	}
+	for index := range left {
+		if !bytes.Equal(left[index], right[index]) {
+			return false
+		}
+	}
+	return true
+}
+
+func operationName(operation int) string {
+	return "operation-" + string(rune('0'+operation))
+}

gdew0154m09/registers.go

@@ -0,0 +1,23 @@
+package gdew0154m09
+
+const (
+	commandPanelSetting       = 0x00
+	commandPowerOff           = 0x02
+	commandPowerOn            = 0x04
+	commandDeepSleep          = 0x07
+	commandDisplayRefresh     = 0x12
+	commandDataStartOld       = 0x10
+	commandDataStartNew       = 0x13
+	commandVCOMDataInterval   = 0x50
+	commandResolutionSetting  = 0x61
+	commandTCONSetting        = 0x60
+	commandPowerSaving        = 0xe3
+	commandPowerSequence      = 0xf3
+	commandBoosterSoftStart   = 0xb6
+	commandUnknownAA          = 0xaa
+	commandUnknownE9          = 0xe9
+	commandFITIInternalCode   = 0x4d
+	deepSleepCheckCode        = 0xa5
+	defaultVCOMDataInterval   = 0xd7
+	deepSleepVCOMDataInterval = 0xf7
+)

smoketest.sh

@@ -29,6 +29,7 @@ tinygo build -size short -o ./build/test.hex -target=microbit ./examples/easyste
 tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/flash/console/spi
 tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/flash/console/qspi
 tinygo build -size short -o ./build/test.hex -target=microbit ./examples/gc9a01/main.go
+tinygo build -size short -o ./build/test.bin -target=esp32-coreboard-v2 ./examples/gdew0154m09/main.go
 tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/gps/i2c/main.go
 tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/gps/uart/main.go
 tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/hcsr04/main.go