drivers/keypad4x4/keypad4x4.go

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
}