ev3js/button.js

LEGO Mindstorms EV3 API for Node.js

var fs = require('fs'),
    EventEmitter = require('events').EventEmitter;

var Button = function() {
    this.poll();
    //this.on('newListener', function(){console.log(this.listenerCount(), arguments);}.bind(this));
};

Button.prototype = new EventEmitter();
(function(){

    this.PATH = '/dev/input/by-path/platform-gpio-keys.0-event';
    this.BUFFER_SIZE = 16;

    this.ESC = 14;
    this.ENTER = 28;
    this.UP = 103;
    this.LEFT = 105;
    this.RIGHT = 106;
    this.DOWN = 108;

    this.polling = false;
    this.pollingTime = 10;

    this.poll = function(){
        fs.open(this.PATH, 'r', function(err, fd){
            if(err){
                throw err;
            }
            this.polling = this.pollingTime;
            (function(){
                var buf = new Buffer(this.BUFFER_SIZE);
                fs.readSync(fd, buf, 0, this.BUFFER_SIZE, null);
                this.parse(buf);
                this.polling && setTimeout(arguments.callee, this.polling);
            }.bind(this))();
            fs.close(fd);
        }.bind(this));
    }

    this.parse = function(data){
        if(data && data[8]){
            this.emit(data[12] ? 'release' : 'press', data[10]);
        }
    };
    
    this.abort = function(){
        this.polling = false;
    };

}.bind(Button.prototype))();

module.exports = Button;