index.js

var net = require('net');
var Put = require('put');

/** @constructor */
function PiFastGpio() {}

/**
 * Connects to the pigpio daemon.
 *
 * This method has to be called before it's possible to do anything with
 * the GPIO pins.
 *
 * The callback will be called when the connection has been established or
 * if an error occurs.
 *
 * @param {string} host - The host to connect to
 * @param {number} port - The port on the host to connect to
 * @param {function} cb - Callback function
 */
PiFastGpio.prototype.connect = function(host, port, cb) {
  this.client = net.connect({host: host, port: port});
  
  this.client.on('connect', function() {
    // Disable the Nagle algoritm
    this.client.setNoDelay(true);

    cb();
  }.bind(this));

  this.client.on('error', function(e) {
    cb(e);
  });
};

/**
 * Half-closes the connection. We might still get some data from the server.
 */
PiFastGpio.prototype.close = function() {
  this.client.end();
};

/**
 * Starts (500-2500) or stops (0) servo pulses on the given gpio pin.
 * 
 * The selected pulsewidth will continue to be transmitted until
 * changed by a subsequent call to set_servo_pulsewidth.
 * 
 * The pulsewidths supported by servos varies and should probably
 * be determined by experiment. A value of 1500 should always be
 * safe and represents the mid-point of rotation.
 * 
 * You can DAMAGE a servo if you command it to move beyond its
 * limits.
 * 
 *     gpio.setServoPulsewidth(17, 0)    # off
 *     gpio.setServoPulsewidth(17, 1000) # safe anti-clockwise
 *     gpio.setServoPulsewidth(17, 1500) # centre
 *     gpio.setServoPulsewidth(17, 2000) # safe clockwise
 *
 * @param {number} userGpio The number of the gpio to address. 0-31.
 * @param {number} pulsewidth The servo pulsewidth to generate
 *              0 (off),
 *              500 (most anti-clockwise) - 2500 (most clockwise).
 */
PiFastGpio.prototype.setServoPulsewidth = function(userGpio, pulsewidth) {
  var cmd = Put()
            .word32le(8) // _PI_CMD_SERVO
            .word32le(userGpio)
            .word32le(pulsewidth)
            .word32le(0); // Not used

  this.client.write(cmd.buffer());
};

/**
 * Starts (non-zero dutycycle) or stops (0) PWM pulses on the gpio.
 *
 *     pi.set_PWM_dutycycle(4,   0) # PWM off
 *     pi.set_PWM_dutycycle(4,  64) # PWM 1/4 on
 *     pi.set_PWM_dutycycle(4, 128) # PWM 1/2 on
 *     pi.set_PWM_dutycycle(4, 192) # PWM 3/4 on
 *     pi.set_PWM_dutycycle(4, 255) # PWM full on
 *
 * @param {number} userGpio The number of the gpio to address. 0-31
 * @param {number} dutycycle The pwm dutycycle to use.
 *              0 (off),
 *              255 (full on)
 */
PiFastGpio.prototype.setPwmDutycycle = function(userGpio, dutycycle) {
  var cmd = Put()
            .word32le(5) // _PI_CMD_PWM
            .word32le(userGpio)
            .word32le(dutycycle)
            .word32le(0);

  this.client.write(cmd.buffer());
};

module.exports = PiFastGpio;