EventDuino

An event-driven Arduino to Node.js adapter.

Support is pretty basic so far:

• Arduino sketch with an event loop
• Extendable protocol
• Basic events
• Reading and writing of pins
• Watching pins for changes and emitting events

Installing

$ npm install eventduino

On the Arduino

Compile and upload the sketch in src/eventdu. This sketch listens for commands and watches for changes to pins via the watch command.

The bulk of the sketch is the parser.

Protocol

The protocol is very minimal. It includes a command, up to ten arguments, and optional comments. Total packet size is currently limited to 1024 bytes.

Currently defined commands and responses:

• INIT - Returned from the Arduino upon init, emits init
• ERROR - Returned from the Arduino upon error, emits exception
• PING - Sends a ping packet to the Arduino
• PONG - Returned from the Arduino from a ping, emits pong
• GET - Send and receive, emits get, arguments are the pin and the value
• SET - Sends a set packet, arguments are the pin and the value
• WATCH - Tells the Arduino to watch for a change on a pin, emits watch with apin and value on change
• UNWATCH - Tells the Arduino to stop watching for a change on a pin
• OK - Ok!

      <packet> ::= <command> <argument> <comment> <EOL>
    
     <command> ::= [0-9a-zA-Z][0-9a-zA-Z]
    
    <argument> ::= <NULL>
                 | ':' [0-9]+ ':' [0-9a-zA-Z]+
                 | <argument>
                 
     <comment> ::= <NULL>
                 | '#' [0-9a-zA-Z]+

Basic Events

The event system is pretty straightforward. On initialization an init event is emitted, at which point further commands can executed.

var eventduino = require('eventduino');

var ardy = new eventduino({ serialport: '/dev/tty.usbmodemfa131' });

ardy.on('pong', function () {
  console.log("PONG!");
});

ardy.on('init', function (args, comment) {
  console.log('Eventduino init version ' + comment);
  ardy.ping();
});

Getting and Setting

Getting and setting of pins is very simple. The pin mode is changed automatically. It is possible to get and set both digital and analog pins.

var eventduino = require('eventduino');

var ardy = new eventduino({ serialport: '/dev/tty.usbmodemfa131' });

ardy.on('get', function (args) {
  console.log("pin " + args[0] + " is set to " + args[1]);
});

ardy.on('init', function (args, comment) {
  console.log('Eventduino init version ' + comment);

  // get the value of analog pin 1
  ardy.get(eventduino.A1);

  // set the LED pin to HIGH (1)
  ardy.set(13, 1);
});

Watching for Changes

Eventduino can be set into watch mode, which will check for any changes to the pin and send a command if one occurs. A watch can be setup on as many pins as required. As analog pins can have a very active variance, a second parameter variance can be passed for analog pins: an event will only be emitted if the value read on watch changes past the variance.

var eventduino = require('eventduino');

var ardy = new eventduino({ serialport: '/dev/tty.usbmodemfa131' });

ardy.on('watch', function (args) {
  console.log("pin " + args[0] + " is now set to " + args[1]);
  
  // stop watching pin 5 on first change
  if (args[0] === 5) {
    ardy.unwatch(eventduino.A5);
    ardy.set(13, 1);
  }
});

ardy.on('init', function (args, comment) {
  console.log('Eventduino init version ' + comment);

  ardy.watch(1);
  // only emit the event if +- 5 on the read
  ardy.watch(eventduino.A5, 5);
});