rpio: basic implementation of Pins and SPI interfaces for Raspberry Pi

examples/rpio/main.go

@@ -0,0 +1,91 @@
+package main
+
+// Example program for the ST7735 display (Waveshare 1.44" LCD HAT) using the rpio driver on a Raspberry Pi.
+// Build command:
+//   GOOS=linux GOARCH=arm64 go build -o rpio-example ./examples/rpio/
+
+import (
+	"fmt"
+	"image/color"
+	"time"
+
+	go_rpio "github.com/stianeikeland/go-rpio/v4"
+	"tinygo.org/x/drivers"
+	"tinygo.org/x/drivers/rpio"
+	"tinygo.org/x/drivers/st7735"
+)
+
+var (
+	black  = color.RGBA{0, 0, 0, 255}
+	colors = [...]color.RGBA{
+		{255, 0, 0, 255},   // red
+		{0, 255, 0, 255},   // green
+		{0, 0, 255, 255},   // blue
+		{255, 255, 0, 255}, // yellow
+	}
+)
+
+func main() {
+	if err := go_rpio.Open(); err != nil {
+		fmt.Println("Error opening GPIO:", err)
+		return
+	}
+	defer go_rpio.Close()
+
+	// Initialize SPI and pins
+	spi := rpio.NewSPI()
+	resetPin := rpio.NewPin(27)
+	dcPin := rpio.NewPin(25)
+	csPin := rpio.NewPin(8)
+	blPin := rpio.NewPin(24)
+
+	rotatePin := rpio.NewPin(20) // middle button on the HAT
+	rotatePin.Pin.PullUp()       // enable pull-up resistor, our wrapper sets only input mode automatically
+
+	// Initialize display
+	device := st7735.New(spi, resetPin, dcPin, csPin, blPin)
+	device.Configure(st7735.Config{
+		Width:        128,
+		Height:       128,
+		Model:        st7735.GREENTAB,
+		RowOffset:    3,
+		ColumnOffset: 2,
+	})
+	device.InvertColors(false)
+	device.EnableBacklight(true)
+	device.IsBGR(true) // no effect w/o rotation!
+	device.SetRotation(st7735.NO_ROTATION)
+
+	width, height := device.Size()
+
+	// Clear display
+	device.FillScreen(black)
+
+	// Draw rectangles in a loop, clockwise rotation of colors
+	pos := 0
+	for {
+		device.FillRectangle(0, 0, width/2, height/2, colors[(pos+0)%len(colors)])              // top left
+		device.FillRectangle(0, height/2, width/2, height/2, colors[(pos+1)%len(colors)])       // bottom left
+		device.FillRectangle(width/2, height/2, width/2, height/2, colors[(pos+2)%len(colors)]) // bottom right
+		device.FillRectangle(width/2, 0, width/2, height/2, colors[(pos+3)%len(colors)])        // top right
+		device.FillRectangle(0, 0, 10, 10, black)                                               // rotation marker
+		pos++
+
+		timeout := time.Now().Add(1 * time.Second)
+		for time.Now().Before(timeout) {
+			// check button pressed
+			if !rotatePin.Get() {
+				currentRotation := device.Rotation()
+				newRotation := (currentRotation + 1) % 4
+				device.SetRotation(drivers.Rotation(newRotation))
+				// wait for button release
+				for !rotatePin.Get() {
+					time.Sleep(10 * time.Millisecond)
+				}
+				break
+			}
+			time.Sleep(50 * time.Millisecond)
+		}
+
+	}
+}

go.mod

@@ -12,6 +12,7 @@ require (
 	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/stianeikeland/go-rpio/v4 v4.6.0
 	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/stianeikeland/go-rpio/v4 v4.6.0 h1:eAJgtw3jTtvn/CqwbC82ntcS+dtzUTgo5qlZKe677EY=
+github.com/stianeikeland/go-rpio/v4 v4.6.0/go.mod h1:A3GvHxC1Om5zaId+HqB3HKqx4K/AqeckxB7qRjxMK7o=
 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=

rpio/pin.go

@@ -0,0 +1,37 @@
+// Implements internal.pin.[Input,Output] interfaces for the Raspberry Pi GPIO pins.
+// Depends on the go-rpio library.
+// Configures pin modes automatically when Get or Set methods are called.
+
+package rpio // import "tinygo.org/x/drivers/rpio"
+
+import go_rpio "github.com/stianeikeland/go-rpio/v4"
+
+type Pin struct {
+	modeSet bool
+	Mode    go_rpio.Mode
+	Pin     go_rpio.Pin
+}
+
+func NewPin(pinNumber int) *Pin {
+	return &Pin{Pin: go_rpio.Pin(pinNumber)}
+}
+
+func (p *Pin) Get() bool {
+	if !p.modeSet || p.Mode != go_rpio.Input {
+		p.Pin.Input()
+		p.Mode = go_rpio.Input
+	}
+	return p.Pin.Read() == go_rpio.High
+}
+
+func (p *Pin) Set(high bool) {
+	if !p.modeSet || p.Mode != go_rpio.Output {
+		p.Pin.Output()
+		p.Mode = go_rpio.Output
+	}
+	state := go_rpio.Low
+	if high {
+		state = go_rpio.High
+	}
+	p.Pin.Write(state)
+}

rpio/spi.go

@@ -0,0 +1,33 @@
+// Implemenmts drivers.SPI interface for the Raspberry Pi.
+// Depends on the go-rpio library.
+
+package rpio // import "tinygo.org/x/drivers/rpio"
+
+import go_rpio "github.com/stianeikeland/go-rpio/v4"
+
+type SPI struct {
+}
+
+func NewSPI() (s *SPI) {
+	if err := go_rpio.SpiBegin(go_rpio.Spi0); err != nil {
+		panic(err)
+	}
+	go_rpio.SpiSpeed(25_000_000) // 25 MHz
+	go_rpio.SpiChipSelect(0)
+	return &SPI{}
+}
+
+func (s *SPI) Tx(w, r []byte) error {
+	data := make([]byte, len(w))
+	copy(data, w)
+	go_rpio.SpiExchange(data)
+	copy(r, data)
+	return nil
+}
+
+func (s *SPI) Transfer(b byte) (byte, error) {
+	w := []byte{b}
+	r := make([]byte, len(w))
+	err := s.Tx(w, r)
+	return r[0], err
+}