epd2in66b: Waveshare 2.66inch E-Paper Display Module (B) for Raspberry Pi Pico (#673)

epd2in66b: add working driver

Co-authored-by: Thomas Richner <[email protected]>

Author: trichner

Makefile

@@ -19,7 +19,7 @@ rwildcard=$(foreach d,$(wildcard $1*),$(call rwildcard,$d/,$2) $(filter $(subst
 # Recursively find all *_test.go files from cwd & reduce to unique dir names
 HAS_TESTS = $(sort $(dir $(call rwildcard,,*_test.go)))
 # Exclude anything we explicitly don't want to test for whatever reason
-EXCLUDE_TESTS = image
+EXCLUDE_TESTS = image waveshare-epd/epd2in66b
 TESTS = $(filter-out $(addsuffix /%,$(EXCLUDE_TESTS)),$(HAS_TESTS))
 
 unit-test:

examples/waveshare-epd/epd2in66b/main.go

@@ -0,0 +1,84 @@
+package main
+
+import (
+	"image/color"
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers"
+	"tinygo.org/x/drivers/waveshare-epd/epd2in66b"
+	"tinygo.org/x/tinyfont"
+	"tinygo.org/x/tinyfont/freemono"
+)
+
+var (
+	black = color.RGBA{0, 0, 0, 0xff}
+	white = color.RGBA{0xff, 0xff, 0xff, 0xff}
+	red   = color.RGBA{0xff, 0, 0, 0xff}
+)
+
+func main() {
+	machine.Serial.Configure(machine.UARTConfig{})
+	time.Sleep(2 * time.Second)
+
+	machine.SPI1.Configure(machine.SPIConfig{
+		Frequency: epd2in66b.Baudrate,
+	})
+
+	println("started")
+
+	// in case you have a Pico module, you can directly use
+	// dev, err := epd2in66b.NewPicoModule()
+
+	display := epd2in66b.New(machine.SPI1)
+
+	cfg := epd2in66b.Config{
+		DataPin:       machine.GP8,
+		ChipSelectPin: machine.GP9,
+		ResetPin:      machine.GP12,
+		BusyPin:       machine.GP13,
+	}
+	err := display.Configure(cfg)
+	if err != nil {
+		panic(err)
+	}
+
+	err = display.Reset()
+	if err != nil {
+		panic(err)
+	}
+
+	println("draw checkerboard")
+	drawCheckerBoard(&display)
+
+	println("draw 'hello'")
+	tinyfont.WriteLineRotated(&display, &freemono.Bold24pt7b, 40, 10, "Hello!", white, tinyfont.ROTATION_90)
+	tinyfont.WriteLineRotated(&display, &freemono.Bold12pt7b, 10, 10, "tinygo rocks", white, tinyfont.ROTATION_90)
+	err = display.Display()
+	if err != nil {
+		panic(err)
+	}
+}
+
+func drawCheckerBoard(display drivers.Displayer) {
+	s := 8
+	width, height := display.Size()
+	for x := 0; x <= int(width)-s; x += s {
+		for y := 0; y <= int(height)-s; y += s {
+			c := red
+			if (x/s)%2 == (y/s)%2 {
+				c = black
+			}
+
+			showRect(display, x, y, s, s, c)
+		}
+	}
+}
+
+func showRect(display drivers.Displayer, x int, y int, w int, h int, c color.RGBA) {
+	for i := x; i < x+w; i++ {
+		for j := y; j < y+h; j++ {
+			display.SetPixel(int16(i), int16(j), c)
+		}
+	}
+}

smoketest.sh

@@ -80,6 +80,7 @@ tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/vl6
 tinygo build -size short -o ./build/test.hex -target=microbit ./examples/waveshare-epd/epd2in13/main.go
 tinygo build -size short -o ./build/test.hex -target=microbit ./examples/waveshare-epd/epd2in13x/main.go
 tinygo build -size short -o ./build/test.hex -target=microbit ./examples/waveshare-epd/epd4in2/main.go
+tinygo build -size short -o ./build/test.hex -target=pico ./examples/waveshare-epd/epd2in66b/main.go
 tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/ws2812
 tinygo build -size short -o ./build/test.bin -target=m5stamp-c3          ./examples/ws2812
 tinygo build -size short -o ./build/test.hex -target=feather-nrf52840 ./examples/is31fl3731/main.go

waveshare-epd/epd2in66b/dev.go

@@ -0,0 +1,287 @@
+// Package epd2in66b implements a driver for the Waveshare 2.66inch E-Paper E-Ink Display Module (B)
+// for Raspberry Pi Pico, 296×152, Red / Black / White
+// Datasheet: https://files.waveshare.com/upload/e/ec/2.66inch-e-paper-b-specification.pdf
+package epd2in66b
+
+import (
+	"image/color"
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers"
+)
+
+const (
+	displayWidth  = 152
+	displayHeight = 296
+)
+
+const Baudrate = 4_000_000 // 4 MHz
+
+type Config struct {
+	ResetPin      machine.Pin
+	DataPin       machine.Pin
+	ChipSelectPin machine.Pin
+	BusyPin       machine.Pin
+}
+
+type Device struct {
+	bus  drivers.SPI
+	cs   machine.Pin
+	dc   machine.Pin
+	rst  machine.Pin
+	busy machine.Pin
+
+	blackBuffer []byte
+	redBuffer   []byte
+}
+
+// New allocates a new device.
+// The bus is expected to be configured and ready for use.
+func New(bus drivers.SPI) Device {
+	pixelCount := displayWidth * displayHeight
+
+	bufLen := pixelCount / 8
+
+	return Device{
+		bus:         bus,
+		blackBuffer: make([]byte, bufLen),
+		redBuffer:   make([]byte, bufLen),
+	}
+}
+
+// Configure configures the device and its pins.
+func (d *Device) Configure(c Config) error {
+	d.cs = c.ChipSelectPin
+	d.dc = c.DataPin
+	d.rst = c.ResetPin
+	d.busy = c.BusyPin
+
+	d.cs.Configure(machine.PinConfig{Mode: machine.PinOutput})
+	d.dc.Configure(machine.PinConfig{Mode: machine.PinOutput})
+	d.rst.Configure(machine.PinConfig{Mode: machine.PinOutput})
+	d.busy.Configure(machine.PinConfig{Mode: machine.PinInput})
+
+	return nil
+}
+
+func (d *Device) Size() (x, y int16) {
+	return displayWidth, displayHeight
+}
+
+// SetPixel modifies the internal buffer in a single pixel.
+// The display has 3 colors: red, black and white
+//
+// - white = RGBA(255,255,255, 1-255)
+// - red = RGBA(1-255,0,0,1-255)
+// - Anything else as black
+func (d *Device) SetPixel(x int16, y int16, c color.RGBA) {
+	if x < 0 || x >= displayWidth || y < 0 || y >= displayHeight {
+		return
+	}
+
+	bytePos, bitPos := pos(x, y, displayWidth)
+
+	if c.R == 0xff && c.G == 0xff && c.B == 0xff && c.A > 0 { // white
+		set(d.blackBuffer, bytePos, bitPos)
+		unset(d.redBuffer, bytePos, bitPos)
+	} else if c.R != 0 && c.G == 0 && c.B == 0 && c.A > 0 { // red-ish
+		set(d.blackBuffer, bytePos, bitPos)
+		set(d.redBuffer, bytePos, bitPos)
+	} else { // black or other
+		unset(d.blackBuffer, bytePos, bitPos)
+		unset(d.redBuffer, bytePos, bitPos)
+	}
+}
+
+func set(buf []byte, bytePos, bitPos int) {
+	buf[bytePos] |= 0x1 << bitPos
+}
+
+func unset(buf []byte, bytePos, bitPos int) {
+	buf[bytePos] &^= 0x1 << bitPos
+}
+
+func pos(x, y, stride int16) (bytePos int, bitPos int) {
+	p := int(x) + int(y)*int(stride)
+	bytePos = p / 8
+
+	// reverse bit position as it is reversed on the device's buffer
+	bitPos = 7 - p%8
+
+	return bytePos, bitPos
+}
+
+func (d *Device) Display() error {
+	// Write RAM (Black White) / RAM 0x24
+	// 1 == white, 0 == black
+	if err := d.sendCommandByte(0x24); err != nil {
+		return err
+	}
+
+	if err := d.sendData(d.blackBuffer); err != nil {
+		return err
+	}
+
+	// Write RAM (RED) / RAM 0x26)
+	// 0 == blank, 1 == red
+	if err := d.sendCommandByte(0x26); err != nil {
+		return err
+	}
+
+	if err := d.sendData(d.redBuffer); err != nil {
+		return err
+	}
+
+	return d.turnOnDisplay()
+}
+
+func (d *Device) ClearBuffer() {
+	fill(d.redBuffer, 0x00)
+	fill(d.blackBuffer, 0xff)
+}
+
+func (d *Device) turnOnDisplay() error {
+	// also documented as 'Master Activation'
+	if err := d.sendCommandByte(0x20); err != nil {
+		return err
+	}
+	d.WaitUntilIdle()
+	return nil
+}
+
+func (d *Device) Reset() error {
+	d.hwReset()
+	d.WaitUntilIdle()
+
+	// soft reset & set defaults
+	if err := d.sendCommandByte(0x12); err != nil {
+		return err
+	}
+	d.WaitUntilIdle()
+
+	// data entry mode setting
+	if err := d.sendCommandSequence([]byte{0x11, 0x03}); err != nil {
+		return err
+	}
+
+	if err := d.setWindow(0, displayWidth-1, 0, displayHeight-1); err != nil {
+		return err
+	}
+
+	// display update control 1 - resolution setting
+	if err := d.sendCommandSequence([]byte{0x21, 0x00, 0x80}); err != nil {
+		return err
+	}
+
+	if err := d.setCursor(0, 0); err != nil {
+		return err
+	}
+	d.WaitUntilIdle()
+
+	return nil
+}
+
+func (d *Device) setCursor(x, y uint16) error {
+	// Set RAM X address counter
+	if err := d.sendCommandSequence([]byte{0x4e, byte(x & 0x1f)}); err != nil {
+		return err
+	}
+
+	// Set RAM Y address counter
+	yLo := byte(y)
+	yHi := byte(y>>8) & 0x1
+	if err := d.sendCommandSequence([]byte{0x4f, yLo, yHi}); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (d *Device) hwReset() {
+	d.rst.High()
+	time.Sleep(50 * time.Millisecond)
+	d.rst.Low()
+	time.Sleep(2 * time.Millisecond)
+	d.rst.High()
+	time.Sleep(50 * time.Millisecond)
+}
+
+func (d *Device) setWindow(xstart, xend, ystart, yend int16) error {
+	// set RAM X-address start / end position
+	d1 := byte((xstart >> 3) & 0x1f)
+	d2 := byte((xend >> 3) & 0x1f)
+	if err := d.sendCommandSequence([]byte{0x44, d1, d2}); err != nil {
+		return err
+	}
+
+	// set RAM Y-address start / end position
+	ystartLo := byte(ystart)
+	ystartHi := byte(ystart>>8) & 0x1
+
+	yendLo := byte(yend)
+	yendHi := byte(yend>>8) & 0x1
+
+	return d.sendCommandSequence([]byte{0x45, ystartLo, ystartHi, yendLo, yendHi})
+}
+
+func (d *Device) WaitUntilIdle() {
+	// give it some time to get busy
+	time.Sleep(50 * time.Millisecond)
+
+	for d.busy.Get() { // high = busy
+		time.Sleep(10 * time.Millisecond)
+	}
+
+	// give it some extra time
+	time.Sleep(50 * time.Millisecond)
+}
+
+// sendCommandSequence sends the first byte in the buffer as a 'command' and all following bytes as data
+func (d *Device) sendCommandSequence(seq []byte) error {
+	err := d.sendCommandByte(seq[0])
+	if err != nil {
+		return err
+	}
+
+	for i := 1; i < len(seq); i++ {
+		err = d.sendDataByte(seq[i])
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (d *Device) sendCommandByte(b byte) error {
+	d.dc.Low()
+	d.cs.Low()
+	_, err := d.bus.Transfer(b)
+	d.cs.High()
+	return err
+}
+
+func (d *Device) sendDataByte(b byte) error {
+	d.dc.High()
+	d.cs.Low()
+	_, err := d.bus.Transfer(b)
+	d.cs.High()
+	return err
+}
+
+func (d *Device) sendData(b []byte) error {
+	d.dc.High()
+	d.cs.Low()
+	err := d.bus.Tx(b, nil)
+	d.cs.High()
+	return err
+}
+
+// fill quickly fills a slice with a given value
+func fill(s []byte, b byte) {
+	s[0] = b
+	for j := 1; j < len(s); j *= 2 {
+		copy(s[j:], s[:j])
+	}
+}