How to use the Raspberry Pi Sense HAT Joystick using golang-evdev

evdev-bobblehat.go

package main

import (
	"flag"
	"fmt"
	"os"
	"os/signal"

	evdev "github.com/gvalkov/golang-evdev"
	screen "github.com/nathany/bobblehat/sense/screen"
	color "github.com/nathany/bobblehat/sense/screen/color"
)

var path = flag.String("path", "/dev/input/event0", "path to the event device")

func main() {
	flag.Parse()

	if !evdev.IsInputDevice(*path) {
		os.Exit(1)
	}

	c := make(chan os.Signal, 1)
	signal.Notify(c, os.Interrupt)
	go func() {
		for range c {
			fmt.Println("Clearing the screen...")
			screen.Clear()
			os.Exit(0)
		}
	}()

	device, err := evdev.Open(*path)
	if err != nil {
		fmt.Printf("Unable to open input device: %s\nError: %v\n", *path, err)
		os.Exit(1)
	}

	fmt.Println(device)

	// Clear the Sense HAT screen
	screen.Clear()

	for {
		events, err := device.Read()
		if err != nil {
			fmt.Printf("device.Read() Error: %v\n", err)
			os.Exit(1)
		}

		for _, ev := range events {
			switch ev.Type {
			case evdev.EV_KEY:
				ke := evdev.NewKeyEvent(&ev)

				if ke.State != evdev.KeyDown {
					continue
				}

				// Create a new framebuffer
				fb := screen.NewFrameBuffer()

				switch ke.Scancode {
				case evdev.KEY_ENTER:
					fmt.Println("⏎ ")
				case evdev.KEY_UP:
					fmt.Println("↑")
					draw(fb, 0, 0, 8, 4, color.New(255, 255, 0))
				case evdev.KEY_DOWN:
					fmt.Println("↓")
					draw(fb, 0, 4, 8, 8, color.New(255, 0, 0))
				case evdev.KEY_LEFT:
					fmt.Println("←")
					draw(fb, 0, 0, 4, 8, color.New(0, 0, 255))
				case evdev.KEY_RIGHT:
					fmt.Println("→")
					draw(fb, 4, 0, 8, 8, color.New(0, 255, 0))
				}

				screen.Draw(fb)
			}
		}
	}
}

func draw(fb *screen.FrameBuffer, a, b, m, n int, c color.Color) {
	for i := a; i < m; i++ {
		for j := b; j < n; j++ {
			fb.SetPixel(i, j, c)
		}
	}
}

Example output:

InputDevice /dev/input/event0 (fd 3)
  name Raspberry Pi Sense HAT Joystick
  phys rpi-sense-joy/input0
  bus 0x0018, vendor 0x0000, product 0x0000, version 0x0000
  events EV_SYN 0, EV_KEY 1, EV_REP 20
↑
→
↓
←
⏎