makeybutton: add driver for MakeyMakey-like button

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

makeybutton/buffer.go

@@ -0,0 +1,46 @@
+package makeybutton
+
+const bufferSize = 10
+
+// Buffer is a buffer to keep track of the most recent readings for a button.
+type Buffer struct {
+	readings [bufferSize]bool
+	index    int
+}
+
+// NewBuffer returns a new buffer.
+func NewBuffer() *Buffer {
+	return &Buffer{}
+}
+
+// Used returns how many bytes in buffer have been used.
+func (b *Buffer) Used() int {
+	return b.index
+}
+
+// Put stores a boolean in the buffer.
+func (b *Buffer) Put(val bool) bool {
+	b.index++
+	if b.index >= bufferSize {
+		b.index = 0
+	}
+
+	b.readings[b.index] = val
+
+	return true
+}
+
+// Avg returns the "average" of all the readings in the buffer, by
+// treating a true as 1 and a false as -1.
+func (b *Buffer) Avg() int {
+	avg := 0
+	for i := 0; i < bufferSize; i++ {
+		if b.readings[i] {
+			avg += 1
+		} else {
+			avg -= 1
+		}
+	}
+
+	return avg
+}