buzzer: add simple buzzer implementation

Signed-off-by: Ron Evans <ron@hybridgroup.com>

buzzer/buzzer.go

@@ -0,0 +1,71 @@
+// Package buzzer provides a very simplistic driver for a connected buzzer or low-fidelity speaker.
+//
+package buzzer // import "tinygo.org/x/drivers/buzzer"
+
+import (
+	"machine"
+
+	"time"
+)
+
+// Device wraps a GPIO connection to a buzzer.
+type Device struct {
+	pin  machine.Pin
+	High bool
+	BPM  float64
+}
+
+// New returns a new buzzer driver given which pin to use
+func New(pin machine.Pin) Device {
+	return Device{
+		pin:  pin,
+		High: false,
+		BPM:  96.0,
+	}
+}
+
+// On sets the buzzer to a high state.
+func (l *Device) On() (err error) {
+	l.pin.Set(true)
+	l.High = true
+	return
+}
+
+// Off sets the buzzer to a low state.
+func (l *Device) Off() (err error) {
+	l.pin.Set(false)
+	l.High = false
+	return
+}
+
+// Toggle sets the buzzer to the opposite of it's current state
+func (l *Device) Toggle() (err error) {
+	if l.High {
+		err = l.Off()
+	} else {
+		err = l.On()
+	}
+	return
+}
+
+// Tone plays a tone of the requested frequency and duration.
+func (l *Device) Tone(hz, duration float64) (err error) {
+	// calculation based off https://www.arduino.cc/en/Tutorial/Melody
+	tone := (1.0 / (2.0 * hz)) * 1000000.0
+
+	tempo := ((60 / l.BPM) * (duration * 1000))
+
+	for i := 0.0; i < tempo*1000; i += tone * 2.0 {
+		if err = l.On(); err != nil {
+			return
+		}
+		time.Sleep(time.Duration(tone) * time.Microsecond)
+
+		if err = l.Off(); err != nil {
+			return
+		}
+		time.Sleep(time.Duration(tone) * time.Microsecond)
+	}
+
+	return
+}