support for Waveshare EPD 2.13" display (black&white only) (#61)

* support for Waveshare EPD 2.13" display (black&white only)

examples/waveshare-epd/epd2in13/main.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"machine"
+
+	"image/color"
+
+	"time"
+
+	"github.com/tinygo-org/drivers/waveshare-epd/epd2in13"
+)
+
+var display epd2in13.Device
+
+func main() {
+	machine.SPI0.Configure(machine.SPIConfig{
+		Frequency: 8000000,
+		Mode:      0,
+	})
+
+	display = epd2in13.New(machine.SPI0, machine.P6, machine.P7, machine.P8, machine.P9)
+	display.Configure(epd2in13.Config{})
+
+	black := color.RGBA{1, 1, 1, 255}
+	white := color.RGBA{0, 0, 0, 255}
+
+	display.ClearBuffer()
+	println("Clear the display")
+	display.ClearDisplay()
+	display.WaitUntilIdle()
+	println("Waiting for 2 seconds")
+	time.Sleep(2 * time.Second)
+
+	// Show a checkered board
+	for i := int16(0); i < 16; i++ {
+		for j := int16(0); j < 25; j++ {
+			if (i+j)%2 == 0 {
+				showRect(i*8, j*10, 8, 10, black)
+			}
+		}
+	}
+	println("Show checkered board")
+	display.Display()
+	display.WaitUntilIdle()
+	println("Waiting for 2 seconds")
+	time.Sleep(2 * time.Second)
+
+	println("Set partial lut")
+	display.SetLUT(false) // partial updates (faster, but with some ghosting)
+	println("Show smaller striped area")
+	for i := int16(40); i < 88; i++ {
+		for j := int16(83); j < 166; j++ {
+			if (i+j)%4 == 0 || (i+j)%4 == 1 {
+				display.SetPixel(i, j, black)
+			} else {
+				display.SetPixel(i, j, white)
+			}
+		}
+	}
+
+	// There are two memory areas in the display, once the display is refreshed, memory areas are auto-toggled.
+	// DisplayRect needs to be called twice
+	display.DisplayRect(40,83,48,83)
+	display.WaitUntilIdle()
+	display.DisplayRect(40,83,48,83)
+	display.WaitUntilIdle()
+
+	println("You could remove power now")
+}
+
+func showRect(x int16, y int16, w int16, h int16, c color.RGBA) {
+	for i := x; i < x+w; i++ {
+		for j := y; j < y+h; j++ {
+			display.SetPixel(i, j, c)
+		}
+	}
+}