examples/apa102: add red Cylon sweep example for Blinkt!

examples/apa102/blinkt-cylon/main.go

@@ -0,0 +1,37 @@
+// Draws a red Cylon sweep on a Pimoroni Blinkt! connected to the 40 pin
+// header of a Waveshare RP2040-PiZero.
+// https://shop.pimoroni.com/products/blinkt
+package main
+
+import (
+	"image/color"
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers/apa102"
+)
+
+const numLEDs = 8
+
+func main() {
+	// Blinkt! uses BCM23 for data and BCM24 for clock. These are not
+	// hardware SPI pins on the RP2040, so use software SPI.
+	leds := apa102.NewSoftwareSPI(machine.GP24, machine.GP23, 1)
+
+	var c [numLEDs]color.RGBA
+	pos, dir := 0, 1
+	for {
+		for i := range c {
+			c[i].R /= 4
+			c[i].A = 0x20
+		}
+		c[pos].R = 0xff
+		leds.WriteColors(c[:])
+
+		if pos+dir < 0 || pos+dir >= numLEDs {
+			dir = -dir
+		}
+		pos += dir
+		time.Sleep(80 * time.Millisecond)
+	}
+}