ECE497 Project: Node.js Weather Station

Revision as of 14:19, 17 February 2012 by Ziyi Zhang (talk | contribs)
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Team members: Yuming Cao, Ziyi Zhang

Executive Summary

Our project aims to implement the emerging nodejs technique (the server side javascript) as a lightweight web server on the beagleboard and accomplish a series of remote monitoring and control of hardware pins like gpio/led/i2c on the beagleboard. There are a lot of things we can do on the nodejs web server, but we try to make it related to our beagleboard hardware interface.

Give two sentences telling what isn't working.

End with a two sentence conclusion.

The sentence count is approximate and only to give an idea of the expected length.

Installation Instructions

1. Here's our github path that includes everything useful to our project:

2. Additional packages installed via opkg:

  • install nodejs
opkg update
opkg install nodejs
opkg install nodejs-dev
  • install node package manager
curl | sh
  • install module
npm install
  • install binary module
npm install binary
  • Include kernel mods.
  • If there is extra hardware needed, include links to where it can be obtained.
  • Here's the guideline to install Cloud9 easily: [1]

User Instructions

Once everything is installed, how do you use the program? Give details here, so if you have a long user manual, link to it here.


Here is where you brag about what your project can do.

Consider including a YouTube demo.

Theory of Operation

Give a high level overview of the structure of your software. Are you using GStreamer? Show a diagram of the pipeline. Are you running multiple tasks? Show what they do and how they interact.

Work Breakdown

1. We've already successfully using JavaScript read and write data to the linux gpio file.

fs.writeFileSync("/sys/class/leds/beagleboard::usr0/trigger", "heartbeat");
fs.writeFileSync("/sys/class/gpio/export", ""+5);

2. Even though we can access to the gpio in the above way, we still need to find someway to access the I2C information. In the I2C exercises, from the C code provided in exercise 5, we can think of the following two options:

a) To translate tons of the C codes into JavaScript...including rewriting the union structures like i2c_smbus_write_byte() and i2c_smbus_read_byte(), which requires far more knowledge in understanding how to translate the underlying hardware detail into upper-level script languages...

b) Try to run the ./myi2c excutable file directly inside nodjs script...

  • It seems that the second way is easier... We've already found a method... We're working on this... turns out this does not work for some reason.
  • At last we successfully excute the ./myi2c file inside our javascript using the following code, the big idea is create another child process to handle it:
var exec  = require('child_process').exec,
child = exec('./myi2c',
  function (error, stdout, stderr) {
    console.log('stdout:', stdout);
    console.log('stderr:', stderr);
    if (error !== null) {
      console.log('exec error:', error);

And the terminal will show the temperature.

3. Now we are going to working on how to show this temperature information on the website so that we can visit it from any place!!!

  • I've successfully done it!!! The pics are already uploaded to the github. Check the following code:
var fs = require("fs");
var http = require("http");

try {
	http.createServer(function(request, response) {

		response.writeHead(200, {"Content-Type": "text/plain"});
		var exec = require('child_process').exec, child;
		child = exec('./myi2c',
	    		function (error, stdout, stderr) {
				console.log('stdout:', stdout);
				console.log('stderr:', stderr);
				if(error != null) {
					console.log('exec error:', error);
} catch(ex3) {

4. The next thing we will do is to refresh the website every other time...

  • We are now able to load html file inside nodejs scripts so that we can put normal HTML stuff inside the web page and load it from server scripts. The following code snippet can accomplish this (borrowed and modified based on Jadon's code):
function loadHTMLFile(uri, res, temp) {
 var filename = path.join(process.cwd(), uri);
  function(exists) {
   if(!exists) {
    res.writeHead(404, {"Content-Type": "text/plain"});
    res.write("404 Not Found\n");

    function(err, file) {
     if(err) {
      res.writeHead(500, {"Content-Type": "text/plain"});
      res.write(err + "\n");
     res.writeHead(200, {"Content-Type": "text/html"});
     var str = ("" + file).replace("<!--%OUTPUT%-->", temp);

And outside the above function, the main routine, we have similar code as listed in 3, but insert the function call:

child = exec('./myi2c',
	    		function (error, stdout, stderr) {
				console.log('stdout:', stdout);
				console.log('stderr:', stderr);
				loadHTMLFile('/index.html', response, stdout);
				if(error != null) {
					console.log('exec error:', error);
  • Now we can update the temperature information on the website, both triggered by a button on the page, and by just automatically refreshing the temperature value whenever the temperature changes. Here is the simple client script for accomplishing this:
<script language="javascript">
<h1>Welcome to the world of Node.js</h1>

<p>Here is the demo of the weather station.</p>
<h2>Current temperature:</h2>
<span id="temperature output"><!--%OUTPUT%--></span>
<form action = "/test.js" method="post">
<input type="submit" value="get temperature">


Give some concluding thoughts about the project. Suggest some future additions that could make it even more interesting.