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Board

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Rick Waldron edited this page Aug 5, 2013 · 15 revisions

The Board class constructs objects that represent the physical board itself. All device objects depend on an initialized and ready board object.

Johnny-Five has been tested on, but is not limited to, the following boards:

See also: Multi-Board Support

Parameters

  • options Optional object of themselves optional parameters.
Property Name Type Value(s) Description Required
id Number, String Any User definable identification no
port String "/dev/ttyAM0", "COM1" Path or name of device port/COM no

Shape

{ 
  ready: ...A boolean value that indicates the readiness of the physical board
  firmata: ...A reference to the protocol layer
  id: ...A user definable id value. Defaults to a generated uid
  pins: ...An array of all pins produced by the capabilities query
  type: ...A string identifier of the board type, one of: "UNO", "MEGA", "LEONARDO" or "UNKOWN"
  repl: ...A reference to the repl session object
  port: A string illustrating the device path or COM address
}

Initializing a Board

The easiest way to initialize a board object is to call the Board constructor function with new. Don't worry about knowing your device's path or COM port, Johnny-Five will figure out which USB the board is plugged into and connect to that automatically.

var five = require("johnny-five"),
    board = new five.Board();

You may optionally specify the port by providing it as a property of the options object parameter:

var five = require("johnny-five"),
    board = new five.Board({ port: "/dev/tty.usbmodemNNNN" });

or

var five = require("johnny-five"),
    board = new five.Board({ port: "COM1" });

Board Ready

Once the board object has been initialized, it must connect to the physical board with a set of handshake steps, once this has completed, the board is ready to communicate with the program. This process is asynchronous, and signified to the program via a "ready" event.

var five = require("johnny-five"),
    board = new five.Board();

board.on("ready", function() {
  // The board can now communicate with this program.
});

Usage

A basic, but complete example usage of the Board constructor:

var five = require("johnny-five"),
    board = new five.Board();

board.on("ready", function() {

  // Create an Led on pin 13
  var led = new five.Led(13);

  // Strobe the pin on/off, defaults to 100ms phases
  led.strobe();

});

API

  • repl This is a property of the board object that represents the automatically generated REPL that's created when a Johnny-Five program is executed. This object has an inject method that may be called as many times as desired.

  • repl.inject(object) Inject objects or values, from the program, into the REPL session.

var five = require("johnny-five"),
    board = new five.Board();

board.on("ready", function() {
  // Initialize an Led object that can be controlled from the REPL session
  this.repl.inject({
    led: new five.Led(13)
  });  
});
/*
  From the terminal...

  > node program.js
  1375291815062 Board Connecting... 
  1375291815081 Serial Found possible serial port /dev/whatever-this-port-is
  1375291815082 Board -> Serialport connected /dev/whatever-this-port-is
  1375291816115 Board <- Serialport ready /dev/whatever-this-port-is
  1375291816116 Repl Initialized 
  >> 
  (Since the led object is available here...)
  >> led.on();
  >> led.off();
  
*/
  • pinMode(pin, mode) Set the mode of a specific pin, one of INPUT, OUTPUT, ANALOG, PWM, SERVO. Mode constants are exposed via the Pin class
Mode Value Constant
INPUT 0 Pin.INPUT
OUTPUT 1 Pin.OUTPUT
ANALOG 2 Pin.ANALOG
PWM 3 Pin.PWM
SERVO 4 Pin.SERVO
```js // Set a pin to INPUT mode var five = require("johnny-five"), board = new five.Board();

board.on("ready", function() {

// pin mode constants are available on the Pin class this.pinMode(13, five.Pin.INPUT); });


- **analogWrite(pin, value)** Write an analog value (0-255) to a digital `pin`.
```js
var five = require("johnny-five"),
    board = new five.Board();

board.on("ready", function() {
  // Assuming an Led is attached to pin 9, this will turn it on at full brightness
  // PWM is the mode used to write ANALOG signals to a digital pin
  this.pinMode(9, five.Pin.PWM);
  this.analogWrite(9, 255);
});
  • analogRead(pin, handler(voltage)) Register a handler to be called whenever the board reports the voltage value (0-1023) of the specified analog pin.
var five = require("johnny-five"),
    board = new five.Board();

board.on("ready", function() {
  // Assuming a sensor is attached to pin "A1"
  this.pinMode(1, five.Pin.ANALOG);
  this.analogRead(1, function(voltage) {
    console.log(voltage);
  });
});
  • digitalWrite(pin, value) Write a digital value (0 or 1) to a digital pin.
var five = require("johnny-five"),
    board = new five.Board();

board.on("ready", function() {
  // Assuming an Led is attached to pin 13, this will turn it on
  this.pinMode(13, five.Pin.OUTPUT);
  this.digitalWrite(13, 1);
});
  • digitalRead(pin, handler(value)) Register a handler to be called whenever the board reports the value (0 or 1) of the specified digital pin.
var five = require("johnny-five"),
    board = new five.Board();

board.on("ready", function() {
  // Assuming a button is attached to pin 9
  this.pinMode(9, five.Pin.INPUT);
  this.digitalRead(9, function(value) {
    console.log(value);
  });
});

  • shiftOut(dataPin, clockPin, isBigEndian, value) Write a byte to dataPin, followed by toggling the clockPin. Understanding Big and Little Endian Byte Order

  • wait(ms, handler()) Register a handler to be called once in another execution turn and after the amount of time specified in milliseconds has passed.

var five = require("johnny-five"),
    board = new five.Board();

board.on("ready", function() {
  // Assuming an Led is attached to pin 13
  this.pinMode(13, five.Pin.OUTPUT);

  // Turn it on...
  this.digitalWrite(13, 1);

  this.wait(1000, function() {
    // Turn it off...
    this.digitalWrite(13, 0);
  });
});
  • loop(ms, handler()) Register a handler to be called repeatedly in another execution turn, every time the specified milliseconds has lapsed.
var five = require("johnny-five"),
    board = new five.Board();

board.on("ready", function() {
  var byte;

  // Assuming an Led is attached to pin 13
  this.pinMode(13, five.Pin.OUTPUT);

  // Homemade strobe
  this.loop(500, function() {
    this.digitalWrite(13, (byte ^= 0x01));
  });
});

Examples

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