add 4x4 keypad driver (#226)

add 4x4 keypad driver

keypad4x4/keypad4x4.go

@@ -0,0 +1,107 @@
+package keypad4x4
+
+import (
+	"machine"
+)
+
+// NoKeyPressed is used, when no key was pressed
+const NoKeyPressed = 255
+
+// Device is used as 4x4 keypad driver
+type Device interface {
+	Configure()
+	GetKey() uint8
+	GetIndices() (int, int)
+}
+
+// device is a driver for 4x4 keypads
+type device struct {
+	inputEnabled bool
+	lastColumn   int
+	lastRow      int
+	columns      [4]machine.Pin
+	rows         [4]machine.Pin
+	mapping      [4][4]uint8
+}
+
+// takes r4 -r1 pins and c4 - c1 pins
+func NewDevice(r4, r3, r2, r1, c4, c3, c2, c1 machine.Pin) Device {
+	result := &device{}
+	result.columns = [4]machine.Pin{c4, c3, c2, c1}
+	result.rows = [4]machine.Pin{r4, r3, r2, r1}
+
+	return result
+}
+
+// Configure sets the column pins as input and the row pins as output
+func (keypad *device) Configure() {
+	inputConfig := machine.PinConfig{Mode: machine.PinInputPullup}
+	for i := range keypad.columns {
+		keypad.columns[i].Configure(inputConfig)
+	}
+
+	outputConfig := machine.PinConfig{Mode: machine.PinOutput}
+	for i := range keypad.rows {
+		keypad.rows[i].Configure(outputConfig)
+		keypad.rows[i].High()
+	}
+
+	keypad.mapping = [4][4]uint8{
+		{0, 1, 2, 3},
+		{4, 5, 6, 7},
+		{8, 9, 10, 11},
+		{12, 13, 14, 15},
+	}
+
+	keypad.inputEnabled = true
+	keypad.lastColumn = -1
+	keypad.lastRow = -1
+}
+
+// GetKey returns the code for the given key.
+// The codes start with 0 at the upper left end of the keypad and end with 15 at the lower right end of the keypad
+// Example:
+// 0	1	2	3
+// 4	5	6	7
+// 8	9	10	11
+// 12	13	14	15
+// returns 255 for no keyPressed
+func (keypad *device) GetKey() uint8 {
+	row, column := keypad.GetIndices()
+	if row == -1 && column == -1 {
+		return NoKeyPressed
+	}
+
+	return keypad.mapping[row][column]
+}
+
+// GetIndices returns the position of the pressed key
+func (keypad *device) GetIndices() (int, int) {
+	for rowIndex, rowPin := range keypad.rows {
+		rowPin.Low()
+
+		for columnIndex := range keypad.columns {
+			columnPin := keypad.columns[columnIndex]
+
+			if !columnPin.Get() && keypad.inputEnabled {
+				keypad.inputEnabled = false
+
+				keypad.lastColumn = columnIndex
+				keypad.lastRow = rowIndex
+
+				return keypad.lastRow, keypad.lastColumn
+			}
+
+			if columnPin.Get() &&
+				columnIndex == keypad.lastColumn &&
+				rowIndex == keypad.lastRow &&
+				!keypad.inputEnabled {
+				keypad.inputEnabled = true
+			}
+		}
+
+		rowPin.High()
+	}
+
+	return -1, -1
+}