brickpi

node-brickpi

Node.js bindings for the BrickPi.

Usage

var BrickPi = require('brickpi')
 
var brickPi = new BrickPi('/dev/ttyAMA0', function() {
  brickPi.led(0).on()
})

Constructor options

All arguments are optional and order is not important.

Pass a string (path to a serial device), an options object and a callback function to invoke when the BrickPi is ready to use.

Default options are as follows:

var brickPi = new BrickPi({
    baudrate: 500000, // the speed of the connection to the BrickPi
    timeout: 10000, // stop the motors if no communication is received in this time period (ms)
    debug: false // whether to print verbose debug output
})

LED

The BrickPi has two LEDs that can be accessed by passing an index to the led function:

var led1 = brickPi.led(0)
var led2 = brickPi.led(1)

An LED supports several methods:

brickPi.led(0).on() // turn the LED on
brickPi.led(0).off() // turn the LED off
brickPi.led(0).toggle() // if the LED is on, turn it off, otherwise turn it on

Motors

var motor = brickPi.addMotor(new BrickPi.Motor(), BrickPi.PORTS.MA)
 
// later
motor.speed(255) // continuous motion - full speed ahead
motor.speed(0) // stop
motor.speed(-255) // reverse
 
// rotation
motor.rotate(180) // rotate 180 degrees
motor.rotate(-180) // rotate 180 degrees in the opposite direction
 
// optionally specify a speed
motor.rotate(180, 255) // rotate 180 degrees at full speed
motor.rotate(180, 128) // rotate 180 degrees at half speed
 
brickPi.once('emergencyStop', function() {
    console.info('stopped!')
})
brickPi.emergencyStop() // immediately stop all motors

Sensors

Valid sensor types are Distance, Light, Sound and Touch.

// add sensors
var distance = brickPi.addSensor(new BrickPi.Sensors.NXT.Distance(), BrickPi.PORTS.S1)
var light = brickPi.addSensor(new BrickPi.Sensors.NXT.Light(), BrickPi.PORTS.S2)
var sound = brickPi.addSensor(new BrickPi.Sensors.NXT.Sound(), BrickPi.PORTS.S3)
var touch = brickPi.addSensor(new BrickPi.Sensors.NXT.Touch(), BrickPi.PORTS.S4)
 
// later
distance.value(function(error, value) {
    // value is 0-255 in cm
}) 
light.value(function(error, value) {
  // value is 0-100 in %
})
sound.value(function(error, value) {
  // value is 0-100 in %
})
touch.value(function(error, value) {
  // value is true or false
})

Notes

What about EV3, NXT2, etc?

I only have the NXT kit, sorry. Hardware donations and/or pull requests gratefully accepted.

Why is the motor control so imprecise?

NXT motors are continuous servos equipped with encoders. This means that you tell the motor how fast to spin then read the encoders to work out what position the motor is in. Once it reaches the desired location, you stop the motor. Because the motor is a mechanical device stopping it involves it slowing down before stopping completely by which point it will most likely be slightly past the desired location. Normal servos do not have this problem because the PWM duty cycle set corresponds to a given orientation of the servo horn.

What about sensor port 5?

The second generation BrickPi has five sensor ports. This driver has been ported from the Python version which doesn't support the fifth sensor port. If a driver that does support it emerges I can add support.