makeybutton: add driver for MakeyMakey-like button

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

makeybutton/button.go

@@ -0,0 +1,79 @@
+// Package makeybutton providers a driver for a button that can be triggered
+// by anything that is conductive by using an ultra high value resistor.
+//
+// Inspired by the amazing MakeyMakey
+// https://makeymakey.com/
+//
+package makeybutton
+
+import "machine"
+
+// ButtonState represents the state of a MakeyButton.
+type ButtonState int
+
+const (
+	NeverPressed ButtonState = 0
+	Press                    = 1
+	Release                  = 2
+)
+
+// ButtonEvent represents when the state of a Button changes.
+type ButtonEvent int
+
+const (
+	NotChanged ButtonEvent = 0
+	Pressed                = 1
+	Released               = 2
+)
+
+// Button is a "button"-like device that acts like a MakeyMakey.
+type Button struct {
+	pin              machine.Pin
+	state            ButtonState
+	readings         *Buffer
+	HighMeansPressed bool
+}
+
+// NewButton creates a new Button.
+func NewButton(pin machine.Pin) *Button {
+	pin.Configure(machine.PinConfig{Mode: machine.PinInput})
+	pin.Set(false)
+
+	return &Button{
+		pin:              pin,
+		state:            NeverPressed,
+		readings:         NewBuffer(),
+		HighMeansPressed: false,
+	}
+}
+
+// Get returns a ButtonEvent based on the most recent state of the button,
+// and if it has changed by being pressed or released.
+func (b *Button) Get() ButtonEvent {
+	// if pin is pulled up, a low value means the key is pressed
+	pressed := !b.pin.Get()
+	if b.HighMeansPressed {
+		// otherwise, a high value means the key is pressed
+		pressed = !pressed
+	}
+
+	avg := b.readings.Avg()
+	b.readings.Put(pressed)
+
+	switch {
+	case pressed && avg > 0:
+		if b.state == Press {
+			return NotChanged
+		}
+
+		b.state = Press
+		return Pressed
+	case !pressed:
+		if b.state == Press {
+			b.state = Release
+			return Released
+		}
+	}
+
+	return NotChanged
+}