examples: add simple i2s example to play sine wave

Signed-off-by: deadprogram <[email protected]>

Author: deadprogram

rp2-pio/examples/i2s/main.go

@@ -0,0 +1,61 @@
+// this example uses the rp2040 I2S peripheral to play a sine wave.
+// It uses a PCM5102A DAC to convert the digital signal to analog.
+// The sine wave is played at 44.1 kHz.
+// The sine wave is played in blocks of 32 samples.
+// The sine wave is played for 500 ms, then paused for 500 ms.
+// The sine wave is played indefinitely.
+// The sine wave is played on both the left and right channels.
+// connect PCM5102A DIN to GPIO2
+// connect PCM5102A BCK to GPIO3
+// connect PCM5102A LCK to GPIO4
+package main
+
+import (
+	"machine"
+	"time"
+
+	pio "github.com/tinygo-org/pio/rp2-pio"
+	"github.com/tinygo-org/pio/rp2-pio/piolib"
+)
+
+const (
+	i2sDataPin  = machine.GPIO2
+	i2sClockPin = machine.GPIO3
+
+	NUM_SAMPLES = 32
+	NUM_BLOCKS  = 5
+)
+
+// sine wave data
+var sine []int16 = []int16{
+	6392, 12539, 18204, 23169, 27244, 30272, 32137, 32767, 32137,
+	30272, 27244, 23169, 18204, 12539, 6392, 0, -6393, -12540,
+	-18205, -23170, -27245, -30273, -32138, -32767, -32138, -30273, -27245,
+	-23170, -18205, -12540, -6393, -1,
+}
+
+func main() {
+	time.Sleep(time.Millisecond * 500)
+
+	sm, _ := pio.PIO0.ClaimStateMachine()
+	i2s, err := piolib.NewI2S(sm, i2sDataPin, i2sClockPin)
+	if err != nil {
+		panic(err.Error())
+	}
+
+	i2s.SetSampleFrequency(44100)
+
+	data := make([]uint32, NUM_SAMPLES*NUM_BLOCKS)
+	for i := 0; i < NUM_SAMPLES*NUM_BLOCKS; i++ {
+		data[i] = uint32(sine[i%NUM_SAMPLES]) | uint32(sine[i%NUM_SAMPLES])<<16
+	}
+
+	// Play the sine wave
+	for {
+		for i := 0; i < 50; i++ {
+			i2s.WriteStereo(data)
+		}
+
+		time.Sleep(time.Millisecond * 500)
+	}
+}