bananenkeyboard/Pi/main.go

package main

import (
	"github.com/faiface/beep"
	"github.com/faiface/beep/effects"
	"github.com/faiface/beep/speaker"
	"github.com/faiface/beep/wav"
	"github.com/tarm/serial"
	"log"
	"math"
	"os"
	"sync"
	"time"
)

var sounds = []*beep.Buffer{
	mustLoadStream("./mini_grand/mini_grand-001.wav"),
	mustLoadStream("./mini_grand/mini_grand-003.wav"),
	mustLoadStream("./mini_grand/mini_grand-005.wav"),
	mustLoadStream("./mini_grand/mini_grand-006.wav"),
	mustLoadStream("./mini_grand/mini_grand-008.wav"),
	mustLoadStream("./mini_grand/mini_grand-010.wav"),
	mustLoadStream("./mini_grand/mini_grand-012.wav"),
	mustLoadStream("./mini_grand/mini_grand-013.wav"),
}

func mustLoadStream(p string) *beep.Buffer {
	f, err := os.Open(p)
	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()

	streamer, format, err := wav.Decode(f)
	if err != nil {
		log.Fatal(err)
	}
	defer streamer.Close()

	newFormat := format
	newFormat.SampleRate = format.SampleRate / 4
	resample := beep.Resample(4, format.SampleRate, newFormat.SampleRate, streamer)

	buffer := beep.NewBuffer(newFormat)
	buffer.Append(resample)

	return buffer
}

type soundWorker struct {
	buffer     *beep.Buffer
	ctrl       *beep.Ctrl
	volume     *effects.Volume
	isRunning  bool
	isStopping bool
	forceEnd   bool
	mtx        sync.Mutex
}

func (w *soundWorker) End() {
	w.isStopping = true
	w.mtx.Lock()
	defer w.mtx.Unlock()

	i := 1
	for w.isRunning {
		if i >= 80 || w.forceEnd {
			break
		}

		w.volume.Volume = float64(1) / math.Pow(10, float64(i))
		i++
	}
	w.isRunning = false
	w.isStopping = false
	w.forceEnd = false
	w.ctrl.Paused = true
}

func (w *soundWorker) Start() {
	if w.isRunning {
		w.forceEnd = true
	}

	w.mtx.Lock()
	defer w.mtx.Unlock()

	w.isRunning = true
	w.ctrl.Streamer.(beep.StreamSeeker).Seek(0)
	w.volume.Volume = 1
	w.ctrl.Paused = false
}

func main() {
	config := &serial.Config{
		Name: "/dev/ttyS0",
		Baud: 115200,
		Size: 8,
	}

	stream, err := serial.OpenPort(config)
	if err != nil {
		log.Fatal(err)
	}

	format := sounds[0].Format()
	if err := speaker.Init(format.SampleRate, format.SampleRate.N(time.Second/100)); err != nil {
		return
	}

	var soundWorkers []*soundWorker

	mixer := beep.Mixer{}
	for _, buffer := range sounds {
		c := &beep.Ctrl{
			Streamer: buffer.Streamer(0, buffer.Len()),
			Paused:   true,
		}

		volume := &effects.Volume{
			Streamer: c,
			Base:     2,
			Volume:   1,
		}

		mixer.Add(volume)

		soundWorkers = append(soundWorkers, &soundWorker{
			buffer: buffer,
			ctrl:   c,
			volume: volume,
		})
	}

	speaker.Play(&mixer)

	c := make(chan byte)

	go func() {
		for b := range c {
			for i, w := range soundWorkers {
				setStop := (b&(1<<i))>>i == 0

				if w.isRunning && !w.isStopping && setStop {
					w.End()
				}

				if !w.isRunning && !setStop {
					w.Start()
				}
			}
		}
	}()

	for {
		buf := make([]byte, 1)
		_, err := stream.Read(buf)
		if err != nil {
			log.Fatal(err)
		}

		c <- buf[0]
	}

}