Blinkt.js

"use strict";

var wpi = require('wiring-pi'),
	DAT = 23,
	CLK = 24,
	Blinkt;

Blinkt = function () {};

/**
 * Connects to the GPIO and sets the GPIO pin modes. Must be called
 * before any other commands. All pixels will start off white at
 * full brightness by default.
 */
Blinkt.prototype.setup = function setup () {
	// Set WPI to GPIO mode
	wpi.setup('gpio');

	// Set pin mode to output
	wpi.pinMode(DAT, wpi.OUTPUT);
	wpi.pinMode(CLK, wpi.OUTPUT);

	this._numPixels = 8;
	this._pixels = [];

	// Init pixels
	for (var i = 0; i < this._numPixels; i++) {
		this.setPixel(i, 255, 255, 255, 1.0);
	}
};

/**
 * Sets all pixels to the passed RGB and brightness values.
 * @param {Number} r The pixel red value between 0 and 255.
 * @param {Number} g The pixel green value between 0 and 255.
 * @param {Number} b The pixel blue value between 0 and 255.
 * @param {Number} a The pixel brightness value between 0.0 and 1.0.
 */
Blinkt.prototype.setAllPixels = function setAllPixels (r, g, b, a) {
	for (var i = 0; i < this._numPixels; i++) {
		this.setPixel(i, r, g, b, a);
	}
};

/**
 * Sets the specified pixel to the passed rgb and brightness level.
 * The pixelNum is an integer between 0 and 7 to indicate the pixel
 * to change.
 * @param {Number} pixelNum The pixel to set RGB and brightness for.
 * An integer value between 0 and 7. Zero is the first pixel, 7 is
 * the last one.
 * @param {Number} r The pixel red value between 0 and 255.
 * @param {Number} g The pixel green value between 0 and 255.
 * @param {Number} b The pixel blue value between 0 and 255.
 * @param {Number} a The pixel brightness value between 0.0 and 1.0.
 */
Blinkt.prototype.setPixel = function setPixel (pixelNum, r, g, b, a) {
	if (a === undefined) {
		if (this._pixels[pixelNum]) {
			// Set a to current level or 1.0 if none exists
			a = this._pixels[pixelNum][3] !== undefined ? this._pixels[pixelNum][3] : 1.0;
		}
	} else {
		a = parseInt((31.0 * a), 10) & 0b11111; // jshint ignore:line
	}

	this._pixels[pixelNum] = [
		parseInt(r, 10) & 255, // jshint ignore:line
		parseInt(g, 10) & 255, // jshint ignore:line
		parseInt(b, 10) & 255, // jshint ignore:line
		a
	];
};

/**
 * Sets the brightness of the pixel specified by pixelNum.
 * @param {Number} pixelNum The pixel to set RGB and brightness for.
 * An integer value between 0 and 7. Zero is the first pixel, 7 is
 * the last one.
 * @param {Number} brightness The pixel brightness value between 0.0
 * and 1.0.
 */
Blinkt.prototype.setBrightness = function setBrightness (pixelNum, brightness) {
	this._pixels[pixelNum][3] = parseInt((31.0 * brightness), 10) & 0b11111; // jshint ignore:line
};

/**
 * Clears the pixel buffer.
 * This is the same as setting all pixels to black.
 * You must also call sendUpdate() if you want to turn Blinkt! off.
 */
Blinkt.prototype.clearAll = function clearAll () {
	for (var i = 0; i < this._numPixels; i++) {
		this.setPixel(i, 0, 0, 0);
	}
};

/**
 * Sends the current pixel settings to the Blinkt! device. Once you
 * have set each pixel RGB and brightness, you MUST call this for the
 * pixels to change on the Blinkt! device.
 */
Blinkt.prototype.sendUpdate = function sendUpdate () {
	var i,
		pixel;

	for (i = 0; i < 4; i++) {
		this._writeByte(0);
	}

	for (i = 0; i < this._numPixels; i++) {
		pixel = this._pixels[i];

		// Brightness
		this._writeByte(0b11100000 | pixel[3]); // jshint ignore:line
		// Blue
		this._writeByte(pixel[2]);
		// Green
		this._writeByte(pixel[1]);
		// Red
		this._writeByte(pixel[0]);
	}

	this._writeByte(0xff);
	this._latch();
};

/**
 * Writes byte data to the GPIO pins.
 * @param {Number} byte The byte value to write.
 * @private
 */
Blinkt.prototype._writeByte = function writeByte (byte) {
	var bit;

	for (var i = 0 ; i < this._numPixels; i++) {
		bit = ((byte & (1 << (7 - i))) > 0) === true ? wpi.HIGH : wpi.LOW; // jshint ignore:line

		wpi.digitalWrite(DAT, bit);
		wpi.digitalWrite(CLK, 1);
		wpi.digitalWrite(CLK, 0);
	}
};

/**
 * Emit exactly enough clock pulses to latch the small dark die APA102s which are weird.
 * @private
 */
Blinkt.prototype._latch = function latch() {
	wpi.digitalWrite(DAT, 0);
	for (var i = 0 ; i < 36; i++) {
		wpi.digitalWrite(CLK, 1);
		wpi.digitalWrite(CLK, 0);
	}
};

module.exports = Blinkt;