From 19e72938fde1d960840a09b5993c4fb7d32652a3 Mon Sep 17 00:00:00 2001
From: Dave Cheney <dave@cheney.net>
Date: Thu, 10 Sep 2026 11:22:59 +1000
Subject: [PATCH] examples: add 2.13in e-Paper V1 demo for RP2040-PiZero

---
 .../waveshare-epd/epd2in13-pizero/main.go     | 159 ++++++++++++++++++
 1 file changed, 159 insertions(+)
 create mode 100644 examples/waveshare-epd/epd2in13-pizero/main.go

diff --git a/examples/waveshare-epd/epd2in13-pizero/main.go b/examples/waveshare-epd/epd2in13-pizero/main.go
new file mode 100644
index 000000000..bbb800399
--- /dev/null
+++ b/examples/waveshare-epd/epd2in13-pizero/main.go
@@ -0,0 +1,159 @@
+// Demo for the Waveshare 2.13in e-Paper HAT V1 on a Waveshare RP2040-PiZero.
+//
+// Panel version.
+//
+// This demo is only for the V1 panel, which uses the IL3820 controller. It
+// uses the epd2in13 driver, which sends the IL3820 init sequence and a 30
+// byte LUT. Later panels use the SSD1680 controller, which needs a different
+// init sequence and a 153 byte LUT, so this demo does not drive them.
+//
+// Identify the panel from the date code on the ribbon cable. V1 shipped from
+// 2015, V2 from 2019 and V3 and V4 from 2021.
+//
+//	V1 (IL3820,  122x250)  works, this demo
+//	V2 (SSD1680, 122x250)  not supported here, try the epd2in9v2 driver
+//	V3 (SSD1680, 122x250)  not supported here, try the epd2in9v2 driver
+//	V4 (SSD1680, 122x250)  not supported here, try the epd2in9v2 driver
+//	2.13in B, C and D variants (three colour or flexible) not supported here,
+//	                       use epd2in13x for the B and C variants
+//
+// 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
+//	Raspberry Pi 40 pin SBC headers  not applicable, this is TinyGo firmware
+//	                                 for a microcontroller, not Linux
+//
+// 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
+//
+// Build and flash:
+//
+//	tinygo flash -target=pico ./examples/waveshare-epd/epd2in13-pizero
+package main
+
+import (
+	"image/color"
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers/waveshare-epd/epd2in13"
+)
+
+const (
+	epdWidth  = 122
+	epdHeight = 250
+)
+
+var (
+	black = color.RGBA{0, 0, 0, 255}
+	white = color.RGBA{255, 255, 255, 255}
+
+	display epd2in13.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("SPI1 configure failed:", err.Error())
+		return
+	}
+
+	display = epd2in13.New(machine.SPI1, machine.GPIO8, machine.GPIO25, machine.GPIO17, machine.GPIO24)
+	display.Configure(epd2in13.Config{
+		Width:  epdWidth,
+		Height: epdHeight,
+	})
+
+	println("clear the display")
+	display.ClearBuffer()
+	display.ClearDisplay()
+	display.WaitUntilIdle()
+
+	println("draw the test pattern")
+	drawTestPattern()
+	display.Display()
+	display.WaitUntilIdle()
+
+	println("done, the display holds the image without power")
+	display.DeepSleep()
+
+	for {
+		time.Sleep(time.Second)
+	}
+}
+
+// drawTestPattern draws a border, two diagonals and a grey scale ramp. A
+// correct panel shows all three. Missing or shifted parts point to a wrong
+// pin, a wrong panel version or a bad ribbon connection.
+func drawTestPattern() {
+	fill(0, 0, epdWidth, epdHeight, white)
+
+	// Border, 2 pixels wide.
+	fill(0, 0, epdWidth, 2, black)
+	fill(0, epdHeight-2, epdWidth, 2, black)
+	fill(0, 0, 2, epdHeight, black)
+	fill(epdWidth-2, 0, 2, epdHeight, black)
+
+	// Diagonals across the full panel.
+	for y := int16(0); y < epdHeight; y++ {
+		x := int16(int32(y) * epdWidth / epdHeight)
+		setPixel(x, y, black)
+		setPixel(epdWidth-1-x, y, black)
+	}
+
+	// Solid black block. This shows the darkest level the panel can reach.
+	fill(16, 20, 40, 40, black)
+
+	// Dither ramp from light to dark in eight steps.
+	for step := int16(0); step < 8; step++ {
+		y0 := 100 + step*16
+		for y := y0; y < y0+14; y++ {
+			for x := int16(10); x < epdWidth-10; x++ {
+				if (x+y*3)%8 < step+1 {
+					setPixel(x, y, black)
+				}
+			}
+		}
+	}
+}
+
+func fill(x, y, w, h int16, c color.RGBA) {
+	for i := x; i < x+w; i++ {
+		for j := y; j < y+h; j++ {
+			setPixel(i, j, c)
+		}
+	}
+}
+
+func setPixel(x, y int16, c color.RGBA) {
+	if x < 0 || x >= epdWidth || y < 0 || y >= epdHeight {
+		return
+	}
+	display.SetPixel(x, y, c)
+}