waveshare-epd: add epd2in7 driver and RP2040-PiZero slideshow demo

examples/waveshare-epd/epd2in7/main.go

@@ -0,0 +1,178 @@
+// Slideshow demo for the Waveshare 2.7in e-Paper HAT V1 on a Waveshare
+// RP2040-PiZero.
+//
+// Panel version.
+//
+// This demo is written for the V1 panel, which uses an IL91874-style
+// controller. It uses the epd2in7 driver, which sends the matching init
+// sequence and 5 part LUT (VCOM, WW, BW, BB, WB). Waveshare has not sold a
+// V2 or later revision of the 2.7in panel, unlike the 2.13in and 2.9in
+// panels, so this driver should match any 2.7in HAT panel.
+//
+//	V1 (IL91874-style, 176x264)  works, this demo
+//
+// Board support.
+//
+// The pin numbers below are only correct for the RP2040-PiZero. Any other
+// board needs its own mapping.
+//
+//	Waveshare RP2040-PiZero          tested, works
+//	Raspberry Pi Pico and Pico W     untested, needs its own pin mapping
+//	                                 because it has no 40 pin header
+//	Other RP2040 boards              untested, needs its own pin mapping
+//
+// The RP2040-PiZero has a Raspberry Pi 40 pin header. Waveshare exchanges
+// GPIO10 and GPIO11 on the header so that RP2040 SPI1 SCK and TX align with
+// the Raspberry Pi SCLK and MOSI positions.
+// Schematic: https://files.waveshare.com/wiki/RP2040-PiZero/RP2040-PiZero.pdf
+//
+// Header to RP2040 GPIO for the e-Paper HAT signals:
+//
+//	pin 11 RST   GPIO17
+//	pin 18 BUSY  GPIO24
+//	pin 19 MOSI  GPIO11 (SPI1 SDO)
+//	pin 22 DC    GPIO25
+//	pin 23 SCLK  GPIO10 (SPI1 SCK)
+//	pin 24 CS    GPIO8
+//
+// Images.
+//
+// Each file in assets/ is a packed 1 bit per pixel image, generated from a
+// source picture by gen.py. The firmware embeds every asset with go:embed
+// and cycles through them in name order, one every slideInterval. File
+// names are numbered so the slideshow order is explicit.
+//
+//	assets/00-hello-mac.bin   the original 1984 Macintosh "hello" screen
+//	assets/01-kanagawa.bin    The Great Wave off Kanagawa, Katsushika Hokusai
+//	assets/02-cccp-stamp.bin  a 1972 Soviet stamp, 15 years of the space era
+//	assets/03-guinea-pig.bin  a guinea pig photo
+//
+// The image is drawn at Rotation270 (Rotation90 landscape, plus 180 degrees
+// for how this panel sits on its connector). Other wiring may need a
+// different rotation to read right way up.
+//
+// Build and flash:
+//
+//	tinygo flash -target=pico ./examples/waveshare-epd/epd2in7
+package main
+
+import (
+	"embed"
+	"encoding/binary"
+	"errors"
+	"image/color"
+	"machine"
+	"sort"
+	"time"
+
+	"tinygo.org/x/drivers"
+	"tinygo.org/x/drivers/waveshare-epd/epd2in7"
+)
+
+//go:embed assets/*.bin
+var assets embed.FS
+
+const slideInterval = 10 * time.Second
+
+var (
+	black = color.RGBA{0, 0, 0, 255}
+	white = color.RGBA{255, 255, 255, 255}
+
+	display epd2in7.Device
+)
+
+func main() {
+	// Wait for the USB serial console to attach so the log is not lost.
+	time.Sleep(3 * time.Second)
+
+	err := machine.SPI1.Configure(machine.SPIConfig{
+		Frequency: 4000000,
+		SCK:       machine.GPIO10,
+		SDO:       machine.GPIO11,
+		SDI:       machine.GPIO12,
+		Mode:      0,
+	})
+	if err != nil {
+		println("SPI configure failed:", err.Error())
+		return
+	}
+
+	display = epd2in7.New(machine.SPI1, machine.GPIO8, machine.GPIO25, machine.GPIO17, machine.GPIO24)
+	display.Configure(epd2in7.Config{
+		Rotation: drivers.Rotation270,
+	})
+
+	names, err := assetNames()
+	if err != nil {
+		println("reading assets failed:", err.Error())
+		return
+	}
+	if len(names) == 0 {
+		println("no assets embedded")
+		return
+	}
+
+	println("epd2in7 slideshow: init done, clearing display")
+	display.ClearBuffer()
+	display.ClearDisplay()
+
+	for i := 0; ; i = (i + 1) % len(names) {
+		name := names[i]
+		println("epd2in7 slideshow: showing", name)
+		if err := showAsset(name); err != nil {
+			println("showing", name, "failed:", err.Error())
+			continue
+		}
+		time.Sleep(slideInterval)
+	}
+}
+
+// assetNames returns the embedded asset file names in sorted order, so the
+// slideshow order is deterministic and reproducible.
+func assetNames() ([]string, error) {
+	entries, err := assets.ReadDir("assets")
+	if err != nil {
+		return nil, err
+	}
+	names := make([]string, 0, len(entries))
+	for _, e := range entries {
+		names = append(names, "assets/"+e.Name())
+	}
+	sort.Strings(names)
+	return names, nil
+}
+
+// showAsset decodes one packed 1bpp asset file and draws it to the panel.
+// The file format is a 4 byte header (uint16 width, uint16 height, little
+// endian) followed by packed pixel bits, MSB first, row-major, bit=1 white.
+func showAsset(name string) error {
+	data, err := assets.ReadFile(name)
+	if err != nil {
+		return err
+	}
+	if len(data) < 4 {
+		return errors.New("asset too short")
+	}
+	w := int16(binary.LittleEndian.Uint16(data[0:2]))
+	h := int16(binary.LittleEndian.Uint16(data[2:4]))
+	bits := data[4:]
+
+	want := (int(w)*int(h) + 7) / 8
+	if len(bits) < want {
+		return errors.New("asset truncated")
+	}
+
+	for y := int16(0); y < h; y++ {
+		for x := int16(0); x < w; x++ {
+			bitpos := int(y)*int(w) + int(x)
+			bit := bits[bitpos/8] & (0x80 >> uint(bitpos%8))
+			if bit != 0 {
+				display.SetPixel(x, y, white)
+			} else {
+				display.SetPixel(x, y, black)
+			}
+		}
+	}
+
+	return display.Display()
+}