start.js

#!/usr/bin/node

/**
 start.js
 Start off script which will load the Firmata driver on Arduino Yun.
 A watchdog is included so we will reset MCU if bridge does not connect Linux and MCU.
 The script also includes an Express Web server allowing to receive and transmit post commands which can be used to communicate with remote gateway just as the SignagePlayer LAN server.

 Test script post via (change IP to your Arduino IP address):
 curl 192.168.1.94:3840/mcu13:1
 curl 192.168.1.94:3840/webapp
 **/

var firmata = require('firmata');
var fs = require('fs');
var spawn = require('child_process').spawn;
var totalCounter = 0;
var timeout = 30;
var maxRebootCycles = 10;
var logFile = '/root/restartCycles.log';
var board = undefined;
var LEDPIN = 13;

var serialReady = false;

console.log('trying to init serial bridge');
var child = spawn('/root/initSerial.js');

child.stdout.on('data', function (msg) {
    if (msg == 'pass') {
        console.log('serial successfully initialized');
        clearInterval(intervals);
        fs.writeFileSync(logFile, 0, 'utf8');
        setTimeout(function(){
            loadFirmata();
        },20000)

    } else {
        updateRebootCycles();
    }
});

child.stderr.on('data', function (data) {
    updateRebootCycles();
});

child.on('close', function (code) {
    // console.log('child process exited with code ' + code);
});

var intervals = setInterval(function () {
    totalCounter++;
    if (totalCounter > timeout) {
        console.log('did not receive response from serial init in time');
        updateRebootCycles();
    }
}, 1000);

/**
 rebootDevice
 reboot micro controller and Linux
 **/
function rebootDevice() {
    console.log('rebooting..');
    spawn('reset-mcu');
    spawn('reboot');
    process.exit();
}

/**
 updateRebootCycles
 **/
function updateRebootCycles() {
    var fileExists = fs.existsSync(logFile);
    if (!fileExists) {
        console.log('did not find restartCycles.log so stopping watchdog');
        process.exit();
    }
    var cycles = fs.readFileSync(logFile, 'utf8');
    cycles++;
    if (cycles > maxRebootCycles) {
        console.log('not rebooting since reached max reboot cycles');
        fs.writeFileSync(logFile, 0, 'utf8');
        process.exit();
    }
    fs.writeFileSync(logFile, cycles, 'utf8');
    console.log('continuing since in cycle ' + cycles);
    rebootDevice();
}

/**
 loadFirmata
 Load the serial driver for Firmata and connect to ttyATH0 to serial over pin 0/1
 Once serial connection is available we load the Express web server
**/
function loadFirmata(){
    board = new firmata.Board("/dev/ttyATH0", function (err) {

        console.log('Firmata connected');
        serialReady = true;
        if (err) {
            console.log(err);
            board.reset();
            return;
        }
        board.pinMode(LEDPIN, board.MODES.OUTPUT);
    });
    loadServer();
}

/**
 loadServer
 Load Express web server
 Listen for remote commands and parse pin/state from URL POST
 **/
function loadServer(){
    var express = require("express");
    var app = express();

    app.all("/mcu:pin", function (req, res) {
        if (!serialReady) {
            res.send("NOTREADY");
            return;
        }
        var pin = (req.params.pin).split(':')[0];
        var state = (req.params.pin).split(':')[1];

        console.log('setting pin ' + pin + ' ' + state + ' ' + getTime());

        if (state == 1) {
            board.digitalWrite(pin, board.HIGH);
        } else {
            board.digitalWrite(pin, board.LOW);
        }
        res.send("OK");

    });

    app.use('/', express.static('/root/public'));

    app.all("/webapp", function (req, res) {
        res.sendfile('/root/public/index.htm')
    });

    var port = process.env.PORT || 3840;
    app.listen(port, function () {
        console.log("Listening on " + port);
    });

}

function getTime() {
    var t = new Date();
    return t.getHours() + ':' + t.getMinutes() + ':' + t.getSeconds();
}