index.js

var i2c = require('i2c');
var sleep = require('sleep');

// LCD i2c interface via PCF8574P
// http://dx.com/p/lcd1602-adapter-board-w-iic-i2c-interface-black-works-with-official-arduino-boards-216865

// https://gist.github.com/chrisnew/6725633
// http://www.espruino.com/HD44780
// http://www.espruino.com/LCD1602
var displayPorts = {
	RS : 0x01,
	E : 0x04,
	D4 : 0x10,
	D5 : 0x20,
	D6 : 0x40,
	D7 : 0x80,

	CHR : 1,
	CMD : 0,

	backlight : 0x08,
	RW : 0x20 // not used
};

var LCD = function (device, address) {
	this.i2c = new i2c(address, {
			device : device
		});

	this.write4(0x30, displayPorts.CMD); //initialization
	this._sleep(200);
	this.write4(0x30, displayPorts.CMD); //initialization
	this._sleep(100);
	this.write4(0x30, displayPorts.CMD); //initialization
	this._sleep(100);
	this.write4( LCD.FUNCTIONSET | LCD._4BITMODE | LCD._2LINE | LCD._5x10DOTS, displayPorts.CMD); //4 bit - 2 line 5x7 matrix
	
	this._sleep(10);
	this.write(LCD.DISPLAYCONTROL | LCD.DISPLAYON, displayPorts.CMD); //turn cursor off 0x0E to enable cursor
	this._sleep(10);
	this.write(LCD.ENTRYMODESET | LCD.ENTRYLEFT, displayPorts.CMD); //shift cursor right
	this._sleep(10);
	this.write(LCD.CLEARDISPLAY, displayPorts.CMD); // LCD clear
	return this;
}

// commands
LCD.CLEARDISPLAY = 0x01;
LCD.RETURNHOME = 0x02;
LCD.ENTRYMODESET = 0x04;
LCD.DISPLAYCONTROL = 0x08;
LCD.CURSORSHIFT = 0x10;
LCD.FUNCTIONSET = 0x20;
LCD.SETCGRAMADDR = 0x40;
LCD.SETDDRAMADDR = 0x80;

//# flags for display entry mode
LCD.ENTRYRIGHT = 0x00;
LCD.ENTRYLEFT = 0x02;
LCD.ENTRYSHIFTINCREMENT = 0x01;
LCD.ENTRYSHIFTDECREMENT = 0x00;

//# flags for display on/off control
LCD.DISPLAYON = 0x04;
LCD.DISPLAYOFF = 0x00;
LCD.CURSORON = 0x02;
LCD.CURSOROFF = 0x00;
LCD.BLINKON = 0x01;
LCD.BLINKOFF = 0x00;

//# flags for display/cursor shift
LCD.DISPLAYMOVE = 0x08;
LCD.CURSORMOVE = 0x00;
LCD.MOVERIGHT = 0x04;
LCD.MOVELEFT = 0x00;

//# flags for function set
LCD._8BITMODE = 0x10;
LCD._4BITMODE = 0x00;
LCD._2LINE = 0x08;
LCD._1LINE = 0x00;
LCD._5x10DOTS = 0x04;
LCD._5x8DOTS = 0x00;

LCD.prototype._sleep = function (milli) {
	sleep.usleep(milli * 1000);
};

LCD.prototype.write4 = function (x, c) {
	function err() {};
	var a = (x & 0xF0); // Use upper 4 bit nibble
	this.i2c.writeByte(a | displayPorts.backlight | c, err);
	this.i2c.writeByte(a | displayPorts.E | displayPorts.backlight | c, err);
	this.i2c.writeByte(a | displayPorts.backlight | c, err);
	this._sleep(1);
}

LCD.prototype.write = function (x, c) {
	this.write4(x, c);
	this.write4(x << 4, c);
	this._sleep(1);
	return this;
}

LCD.prototype.clear = function () {
	return this.write(LCD.CLEARDISPLAY, displayPorts.CMD);
}

LCD.prototype.print = function (str) {
	if (typeof str == 'string') {
		for (var i = 0; i < str.length; i++) {
			var c = str[i].charCodeAt(0);
			this.write(c, displayPorts.CHR);
			this._sleep(1);
		}
	}
	return this;
}
/** flashing block for the current cursor */
LCD.prototype.cursorFull = function () {
	return this.write(LCD.DISPLAYCONTROL | LCD.DISPLAYON | LCD.CURSORON | LCD.BLINKON, displayPorts.CMD);
}
/** small line under the current cursor */
LCD.prototype.cursorUnder = function () {
	return this.write(LCD.DISPLAYCONTROL |  LCD.DISPLAYON | LCD.CURSORON | LCD.BLINKOFF, displayPorts.CMD);
}
/** set cursor pos, top left = 0,0 */
LCD.prototype.setCursor = function (x, y) {
	var l = [0x00, 0x40, 0x14, 0x54];
	return this.write(LCD.SETDDRAMADDR | (l[y] + x), displayPorts.CMD);
}
/** set cursor to 0,0 */
LCD.prototype.home = function () {
	var l = [0x00, 0x40, 0x14, 0x54];
	return this.write(LCD.SETDDRAMADDR | 0x00, displayPorts.CMD);
}
/** Turn underline cursor off */
LCD.prototype.blinkOff = function () {
	return this.write( LCD.DISPLAYCONTROL | LCD.DISPLAYON | LCD.CURSOROFF | LCD.BLINKOFF, displayPorts.CMD);
}
/** Turn underline cursor on */
LCD.prototype.blinkOn = function () {
	return this.write( LCD.DISPLAYCONTROL | LCD.DISPLAYON | LCD.CURSORON | LCD.BLINKOFF, displayPorts.CMD);
}
/** Turn block cursor off */
LCD.prototype.cursorOff = function () {
	return this.write( LCD.DISPLAYCONTROL | LCD.DISPLAYON | LCD.CURSOROFF | LCD.BLINKON, displayPorts.CMD);
}
/** Turn block cursor on */
LCD.prototype.cursorOn = function () {
	return this.write( LCD.DISPLAYCONTROL | LCD.DISPLAYON | LCD.CURSORON | LCD.BLINKON, displayPorts.CMD);
}
/** setBacklight */
LCD.prototype.setBacklight = function (val) {
	if (val > 0) {
		displayPorts.backlight = 0x08;
	} else {
		displayPorts.backlight = 0x00;
	}
	return this.write(LCD.DISPLAYCONTROL, displayPorts.CMD);
}
/** setContrast stub */
LCD.prototype.setContrast = function (val) {
	return this.write(LCD.DISPLAYCONTROL, displayPorts.CMD);
}
/** Turn display off */
LCD.prototype.off = function () {
	displayPorts.backlight = 0x00;
	return this.write(LCD.DISPLAYCONTROL | LCD.DISPLAYOFF, displayPorts.CMD);
}
/** Turn display on */
LCD.prototype.on = function () {
	displayPorts.backlight = 0x08;
	return this.write(LCD.DISPLAYCONTROL | LCD.DISPLAYON, displayPorts.CMD);
}
/** set special character 0..7, data is an array(8) of bytes, and then return to home addr */
LCD.prototype.createChar = function (ch, data) {
	this.write(LCD.SETCGRAMADDR | ((ch & 7) << 3), displayPorts.CMD);
	for (var i = 0; i < 8; i++)
		this.write(data[i], displayPorts.CHR);
	return this.write(LCD.SETDDRAMADDR, displayPorts.CMD);
}

module.exports = LCD;