neopixel: add PIO-based WS2812B driver for RP2040/RP2350

examples/neopixel/main.go

@@ -0,0 +1,36 @@
+// Demonstrates NeoPixel (WS2812B) RGB LED control.
+//
+// Tested on Waveshare RP2350-LCD-1.47 with onboard RGB LED on GP22.
+//
+// To flash:
+//
+//	tinygo flash -target=pico2 ./examples/neopixel/
+package main
+
+import (
+	"image/color"
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers/neopixel"
+)
+
+func main() {
+	pixel, err := neopixel.New(machine.GP22, 1)
+	if err != nil {
+		panic(err)
+	}
+	pixel.SetBrightness(50)
+
+	colors := []color.RGBA{
+		{R: 255, G: 0, B: 0},
+		{R: 0, G: 255, B: 0},
+		{R: 0, G: 0, B: 255},
+	}
+
+	for i := 0; ; i = (i + 1) % 3 {
+		pixel.SetPixel(0, colors[i])
+		pixel.Show()
+		time.Sleep(time.Second)
+	}
+}

go.mod

@@ -1,17 +1,16 @@
 module tinygo.org/x/drivers
 
-
 go 1.22.1
 
 toolchain go1.23.1
 
-
 require (
 	github.com/eclipse/paho.mqtt.golang v1.2.0
 	github.com/frankban/quicktest v1.10.2
 	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510
 	github.com/orsinium-labs/tinymath v1.1.0
 	github.com/soypat/natiu-mqtt v0.5.1
+	github.com/tinygo-org/pio v0.3.0
 	golang.org/x/exp v0.0.0-20241204233417-43b7b7cde48d
 	golang.org/x/net v0.33.0
 	tinygo.org/x/tinyfont v0.3.0

go.sum

@@ -17,6 +17,8 @@ github.com/orsinium-labs/tinymath v1.1.0 h1:KomdsyLHB7vE3f1nRAJF2dyf1m/gnM2HxfTe
 github.com/orsinium-labs/tinymath v1.1.0/go.mod h1:WPXX6ei3KSXG7JfA03a+ekCYaY9SWN4I+JRl2p6ck+A=
 github.com/soypat/natiu-mqtt v0.5.1 h1:rwaDmlvjzD2+3MCOjMZc4QEkDkNwDzbct2TJbpz+TPc=
 github.com/soypat/natiu-mqtt v0.5.1/go.mod h1:xEta+cwop9izVCW7xOx2W+ct9PRMqr0gNVkvBPnQTc4=
+github.com/tinygo-org/pio v0.3.0 h1:opEnOtw58KGB4RJD3/n/Rd0/djYGX3DeJiXLI6y/yDI=
+github.com/tinygo-org/pio v0.3.0/go.mod h1:wf6c6lKZp+pQOzKKcpzchmRuhiMc27ABRuo7KVnaMFU=
 github.com/valyala/fastjson v1.6.3/go.mod h1:CLCAqky6SMuOcxStkYQvblddUtoRxhYMGLrsQns1aXY=
 golang.org/x/exp v0.0.0-20241204233417-43b7b7cde48d h1:0olWaB5pg3+oychR51GUVCEsGkeCU/2JxjBgIo4f3M0=
 golang.org/x/exp v0.0.0-20241204233417-43b7b7cde48d/go.mod h1:qj5a5QZpwLU2NLQudwIN5koi3beDhSAlJwa67PuM98c=

neopixel/neopixel.go

@@ -0,0 +1,80 @@
+// Package neopixel implements a driver for WS2812B/NeoPixel RGB LED strips.
+//
+// On RP2040/RP2350, it uses PIO for hardware-timed control.
+// On other platforms, it falls back to the ws2812 bit-bang driver.
+package neopixel // import "tinygo.org/x/drivers/neopixel"
+
+import (
+	"image/color"
+	"machine"
+)
+
+// Device controls a strip of WS2812B/NeoPixel LEDs.
+type Device struct {
+	pin        machine.Pin
+	pixels     []color.RGBA
+	brightness uint8
+	backend    backend
+}
+
+// backend is the platform-specific implementation for sending pixel data.
+type backend interface {
+	init(pin machine.Pin) error
+	writePixels(pixels []color.RGBA, brightness uint8) error
+}
+
+// New creates a new NeoPixel device on the given pin with the specified number of pixels.
+func New(pin machine.Pin, numPixels int) (*Device, error) {
+	d := &Device{
+		pin:        pin,
+		pixels:     make([]color.RGBA, numPixels),
+		brightness: 255,
+		backend:    newBackend(),
+	}
+	if err := d.backend.init(pin); err != nil {
+		return nil, err
+	}
+	return d, nil
+}
+
+// SetPixel sets the color of pixel at index i.
+func (d *Device) SetPixel(i int, c color.RGBA) {
+	if i >= 0 && i < len(d.pixels) {
+		d.pixels[i] = c
+	}
+}
+
+// Show sends the current pixel buffer to the LED strip.
+func (d *Device) Show() error {
+	return d.backend.writePixels(d.pixels, d.brightness)
+}
+
+// SetBrightness sets the global brightness (0-255).
+func (d *Device) SetBrightness(b uint8) {
+	d.brightness = b
+}
+
+// Fill sets all pixels to the given color.
+func (d *Device) Fill(c color.RGBA) {
+	for i := range d.pixels {
+		d.pixels[i] = c
+	}
+}
+
+// Clear turns off all pixels.
+func (d *Device) Clear() {
+	d.Fill(color.RGBA{})
+}
+
+// NumPixels returns the number of pixels in the strip.
+func (d *Device) NumPixels() int {
+	return len(d.pixels)
+}
+
+// applyBrightness scales a color by the brightness value.
+func applyBrightness(c color.RGBA, brightness uint8) (r, g, b uint8) {
+	r = uint8((uint16(c.R) * uint16(brightness)) >> 8)
+	g = uint8((uint16(c.G) * uint16(brightness)) >> 8)
+	b = uint8((uint16(c.B) * uint16(brightness)) >> 8)
+	return
+}

neopixel/neopixel_other.go

@@ -0,0 +1,33 @@
+//go:build !rp2040 && !rp2350
+
+package neopixel
+
+import (
+	"image/color"
+	"machine"
+
+	"tinygo.org/x/drivers/ws2812"
+)
+
+type otherBackend struct {
+	ws ws2812.Device
+}
+
+func newBackend() backend {
+	return &otherBackend{}
+}
+
+func (b *otherBackend) init(pin machine.Pin) error {
+	pin.Configure(machine.PinConfig{Mode: machine.PinOutput})
+	b.ws = ws2812.NewWS2812(pin)
+	return nil
+}
+
+func (b *otherBackend) writePixels(pixels []color.RGBA, brightness uint8) error {
+	adjusted := make([]color.RGBA, len(pixels))
+	for i, c := range pixels {
+		r, g, bl := applyBrightness(c, brightness)
+		adjusted[i] = color.RGBA{R: r, G: g, B: bl}
+	}
+	return b.ws.WriteColors(adjusted)
+}

neopixel/neopixel_rp2.go

@@ -0,0 +1,40 @@
+//go:build rp2040 || rp2350
+
+package neopixel
+
+import (
+	"image/color"
+	"machine"
+
+	pio "github.com/tinygo-org/pio/rp2-pio"
+	"github.com/tinygo-org/pio/rp2-pio/piolib"
+)
+
+type rp2Backend struct {
+	ws *piolib.WS2812B
+}
+
+func newBackend() backend {
+	return &rp2Backend{}
+}
+
+func (b *rp2Backend) init(pin machine.Pin) error {
+	sm, err := pio.PIO0.ClaimStateMachine()
+	if err != nil {
+		return err
+	}
+	ws, err := piolib.NewWS2812B(sm, pin)
+	if err != nil {
+		return err
+	}
+	b.ws = ws
+	return nil
+}
+
+func (b *rp2Backend) writePixels(pixels []color.RGBA, brightness uint8) error {
+	for _, c := range pixels {
+		r, g, bl := applyBrightness(c, brightness)
+		b.ws.PutRGB(r, g, bl)
+	}
+	return nil
+}