SparkFun: ITG-3200,Triple-Axis Gyro Display

Overview
This project show how the ITG-3200, a three-axis gyro sensor, can read and displayed using the beagle bone, a web browser and node.js. This project expands upon what was documented in SparkFun:_ITG-3200,Triple-Axis_Gyro.







Introduction
The goal here is to add a web-based graphical display to the gyroscopic sensor. Using examples of node.js servers that display realtime data from the beagle, I have altered the example code to display specifically the three axes of rotation for the gyroscope as well as in addition the internal temperature of the sensor itself.


 * buttonBox.js, buttonBox.html
 * This is a bone-based example that reads a gpio port, analog in and an i2c device and displays the output in a web browser.These will be there two main files that will contain many of my alterations.

Running the code
First off, you'll need to download the code through the get hub repository onto a local directory within your Beagle bone. You will then need to navigate to: beagle$ cd ~/MiniProject04/node.js/realtime beagle$ opkg update beagle$ opkg install nodejs (Don't install node, it's not what you think.)

On the Bone: beagle$ node buttonBox.js

Simply press ‘CTRL’ + ‘C’ to quit the program.

Connecting to the Bone
Then point a browser to beaglebone.local:8081. The default port is 8081. You can change it if you like.

How it works
The prior examples included the script within the HTML file that polled the server continuously for data updates. However I have altered the code within the HTML file as well as the .js file to allow the server to be so fully responsible for pushing the data to the client.

Another alteration I have made is to alter the I2C function that is called to acquisition the sensor data. Using the source code within mini project two, I have made a stripped-down version that simply returns all the relevant registers within the sensor. This is interpreted as a string within the server's .js file and is streamed to the client browser where the script parses the relevant information to each specific axis and temperature variable. This is then plotted on the grass and rendered on-screen over time.



Node.js Code
The code shown below is part sample code to demonstrate reading the registers via I2C and displaying the data with node.js. The alteration that has been made is to specify a timeout period for the server, as well as an additional function that will execute the terminal commands required to poll the gyroscopic sensor in return its register values. The code will also zero out the gyro to account for the internal bias the gyro might have just being stationary and level.

One alteration you'll need to make is to change the path the exec function with in the pushMessage function calls the custom c program to read the I2C buss. Just change the path to point to the excusable you compile with gcc using available MiniProject02.c file within the same directory as the HTML and node.js files, all the necessary header files are included as well.

// From Getting Started With node.js and socket.io // http://codehenge.net/blog/2011/12/getting-started-with-node-js-and-socket-io-v0-7-part-2/ "use strict";

var http = require('http'), url = require('url'), fs = require('fs'), exec = require('child_process').exec, server, connectCount = 0;	// Number of connections to server

server = http.createServer(function (req, res) { // server code   var path = url.parse(req.url).pathname;    console.log("path: " + path);    switch (path) {    case '/':        res.writeHead(200, {'Content-Type': 'text/html'});        res.write(' Hello! TryButton Box Demo');

res.end; break;

default:		// This is so all the files will be sent. fs.readFile(__dirname + path, function (err, data) {           if (err) {return send404(res); } //            console.log("path2: " + path);            res.write(data, 'utf8');            res.end;        }); break;

} });

var send404 = function (res) { res.writeHead(404); res.write('404'); res.end; };

server.listen(8081);

// socket.io, I choose you var io = require('socket.io').listen(server); io.set('log level', 2);

// on a 'connection' event io.sockets.on('connection', function (socket) {   var frameCount = 0;	// Counts the frames from arecord    var lastFrame = 0;	// Last frame sent to browser    console.log("Connection " + socket.id + " accepted."); //    console.log("socket: " + socket);

// now that we have our connected 'socket' object, we can // define its event handlers

// Make sure some needed files are there // The path to the analog devices changed from A5 to A6. Check both. var ainPath = "/sys/devices/platform/omap/tsc/"; //   if(!fs.existsSync(ainPath)) { //       ainPath = "/sys/devices/platform/tsc/"; //       if(!fs.existsSync(ainPath)) { //           throw "Can't find " + ainPath; //       } //    }    // Make sure gpio 7 is available. exec("echo 7 > /sys/class/gpio/export");

// Send value every time a 'message' is received. socket.on('ain', function (ainNum) { //       var ainPath = "/sys/devices/platform/omap/tsc/ain" + ainNum;        fs.readFile(ainPath + "ain" + ainNum, 'base64', function(err, data) { if(err) throw err; socket.emit('ain', data); //           console.log('emitted ain: ' + data); });   });

socket.on('gpio', function (gpioNum) {       var gpioPath = "/sys/class/gpio/gpio" + gpioNum + "/value";        fs.readFile(gpioPath, 'base64', function(err, data) { if (err) throw err; socket.emit('gpio', data); //           console.log('emitted gpio: ' + data); });   });

socket.on('i2c', function (i2cNum) { //       console.log('Got i2c request:' + i2cNum);        exec('i2cget -y 3 ' + i2cNum + ' 0 w', function (error, stdout, stderr) { //		The TMP102 returns a 12 bit value with the digits swapped stdout = '0x' + stdout.substring(4,6) + stdout.substring(2,4); //               console.log('i2cget: "' + stdout + '"'); if(error) { console.log('error: ' + error); } if(stderr) {console.log('stderr: ' + stderr); } socket.emit('i2c', stdout); });   });

socket.on('led', function (ledNum) {       var ledPath = "/sys/class/leds/beaglebone::usr" + ledNum + "/brightness"; //        console.log('LED: ' + ledPath);        fs.readFile(ledPath, 'utf8', function (err, data) { if(err) throw err; data = data.substring(0,1) === "1" ? "0" : "1"; //           console.log("LED%d: %s", ledNum, data); fs.writeFile(ledPath, data); });   });

var updateInterval = 100; function pushMessage { //       console.log('Got i2c request:' + 6); exec('/home/root/ECE497/MiniProject04/node.js/realtime/./a.out 0 0 ' + 3,           function (error, stdout, stderr) {		console.log('stdout:' + stdout);		//console.log('stdout:' + parseFloat(stdout.substring(51,58))/100.0);                if(error) { console.log('error: ' + error); }                if(stderr) {console.log('stderr: ' + stderr); }                socket.emit('i2c', stdout);            }); setTimeout(pushMessage, updateInterval); }   pushMessage;

socket.on('disconnect', function {        console.log("Connection " + socket.id + " terminated.");        connectCount--;        if(connectCount === 0) {        }        console.log("connectCount = " + connectCount);    });

connectCount++; console.log("connectCount = " + connectCount); });

HTML Code
This file is altered from example code and contains all the necessary formatting for the user interface and data representation. A also contains the script necessary to parse the string containing the sensor data sent by the server.

<!doctype html> Gyro Demo

 

    Gyro Demo   Connect <button id="disconnect" onClick='disconnect'>Disconnect Analog: <input id="ainNum" type="text" value="" style="text-align: right; width:2em"> gpio: <input id="gpioNum" type="text" value="" style="text-align: right; width:2em"> i2c: <input id="i2cNum" type="text" value="" style="text-align: right; width:3em">

<button id="led0" onClick='led(0)'/>LED 0 <button id="led1" onClick='led(1)'/>LED 1 <button id="led2" onClick='led(2)'/>LED 2 <button id="led3" onClick='led(3)'/>LED 3

Button Box demo from the <a href="http://elinux.org/index.php?title=Category:ECE497" target="_blank">32-bit Embedded Linux Class</a>. In this demo, the beagle bone pushes it sensor data to the web browser. Try moving the gyro or touching it to change its temprature. Try double-clicking to zoom and click and dragging to pan. <a href="http://beagleboard.org" target="_blank"> <img src="beagle-hd-logo.gif" width=200 align="right"></a> Waiting for input <a href="http://www.ti.com/sitara" target="_blank"> <img src="hdr_ti_logo.gif" width=200 align="right"></a> message By Ruffin White

var socket; var firstconnect = true, fs = 8000, Ts = 1/fs*1000, samples = 100, plotTop, plotBot, ainData = [], iain = 0, gpioData = [], igpio = 0, i2cXData = [], ii2cX = 0, i2cYData = [], ii2cY = 0, i2cZData = [], ii2cZ = 0, i2cTData = [], ii2cT = 0, gpioNum = 7, ainNum = 6, i2cNum = "0x48"; ainData[samples] = 0; gpioData[samples] = 0; i2cXData[samples] = 0; i2cYData[samples] = 0; i2cZData[samples] = 0; i2cTData[samples] = 0;

function connect { if(firstconnect) { socket = io.connect(null);

socket.on('message', function(data)           { status_update("Received: message");}); socket.on('connect', function           { status_update("Connected to Server"); }); socket.on('disconnect', function           { status_update("Disconnected from Server"); }); socket.on('reconnect', function           { status_update("Reconnected to Server"); }); socket.on('reconnecting', function( nextRetry )           { status_update("Reconnecting in " + nextRetry/1000 + " s"); }); socket.on('reconnect_failed', function           { message("Reconnect Failed"); });

socket.on('ain', ain); socket.on('gpio', gpio); socket.on('i2c', i2c);

firstconnect = false; }     else { socket.socket.reconnect; }   }

function disconnect { socket.disconnect; }

function led(ledNum) { socket.emit('led', ledNum); }

// When new data arrived, convert it and plot it. function ain(data) { data = atob(data)/4096 * 1.8; data = isNaN(data) ? 0 : data; //       status_update("ain: " + data); ainData[iain] = [iain, data]; iain++; if(iain >= samples) { iain = 0; ainData = []; }       plotTop.setData([ ainData, gpioData ]); plotTop.draw; }

function gpio(data) { data = atob(data); //       status_update("gpio: " + data); gpioData[igpio] = [igpio, data]; igpio++; if(igpio >= samples) { igpio = 0; gpioData = []; }       plotTop.setData([ ainData, gpioData ]); plotTop.draw; } //gyroX: -00026 gyroY: -00012 gyroZ: 000073 gyroTemp: 002602

function i2c(data) { Xdata = parseInt(data.substring(6,12)); Ydata = parseInt(data.substring(20,26)); Zdata = parseInt(data.substring(34,40)); Tdata = parseInt(data.substring(51,56)); i2cXData[ii2cX] = [ii2cX, Xdata]; i2cYData[ii2cY] = [ii2cY, Ydata]; i2cZData[ii2cZ] = [ii2cZ, Zdata]; i2cTData[ii2cT] = [ii2cT, Tdata]; ii2cX++; if(ii2cX >= samples) { ii2cX = 0; i2cXData = []; }       i2cXData[ii2cY] = [ii2cY, Xdata]; ii2cY++; if(ii2cY >= samples) { ii2cY = 0; i2cYData = []; }       i2cXData[ii2cZ] = [ii2cZ, Xdata]; ii2cZ++; if(ii2cZ >= samples) { ii2cZ = 0; i2cZData = []; }       i2cXData[ii2cT] = [ii2cT, Xdata]; ii2cT++; if(ii2cT >= samples) { ii2cT = 0; i2cTData = []; }       plotBot.setData([ i2cXData, i2cYData, i2cZData]); plotBot.draw; plotTop.setData([ i2cTData ]); plotTop.draw; }

function status_update(txt){ document.getElementById('status').innerHTML = txt; }

function send{ socket.emit("ain", "Hello Server!"); };

connect;

$(function {

function initPlotData { // zip the generated y values with the x values var result = []; for (var i = 0; i <= samples; i++) result[i] = [i, 0]; return result; }

// setup control widget $("#ainNum").val(ainNum).change(function {        ainNum = $(this).val;    });

$("#gpioNum").val(gpioNum).change(function {        gpioNum = $(this).val;    });

$("#i2cNum").val(i2cNum).change(function {        i2cNum = $(this).val;    });

var updateTopInterval = 100; $("#updateTopInterval").val(updateTopInterval).change(function {        var v = $(this).val;        if (v && !isNaN(+v)) {            updateTopInterval = +v;            if (updateTopInterval < 25)                updateTopInterval = 25;            if (updateTopInterval > 2000)                updateTopInterval = 2000;            $(this).val("" + updateTopInterval);        }    });

var updateBotInterval = 100; $("#updateBotInterval").val(updateBotInterval).change(function {        var v = $(this).val;        if (v && !isNaN(+v)) {            updateBotInterval = +v;            if (updateBotInterval < 25)                updateBotInterval = 25;            if (updateBotInterval > 2000)                updateBotInterval = 2000;            $(this).val("" + updateBotInterval);        }    });

// setup plot var optionsTop = { series: { shadowSize: 0, // drawing is faster without shadows points: { show: false}, lines: { show: true, lineWidth: 5}, },        yaxis:	{ min: 10, max: 35, zoomRange: [10, 256], panRange: [-128, 128] }, xaxis:	{ show: true, zoomRange: [10, 100], panRange: [0, 100] }, legend:	{ position: "sw" }, zoom:	{ interactive: true, amount: 1.1 }, pan:	{ interactive: true } };   plotTop = $.plot($("#plotTop"),         [           { data:  initPlotData,             label: "GyroTemp" }        ],            optionsTop);

var optionsBot = { series: { shadowSize: 0, // drawing is faster without shadows points: { show: false}, lines: { show: true, lineWidth: 5}, //color: 2 },        yaxis:	{ min: -100, max: 100, zoomRange: [10, 256], panRange: [60, 100] }, xaxis:	{ show: true, zoomRange: [10, 100], panRange: [0, 100] }, legend:	{ position: "sw" }, zoom:	{ interactive: true, amount: 1.1 }, pan:	{ interactive: true } };   plotBot = $.plot($("#plotBot"),         [           { data:  initPlotData,            label: "GyroX"},          { data:  initPlotData,            label: "GyroY"},          { data:  initPlotData,            label: "GyroZ"}        ],            optionsBot);

// Request data every updateInterval ms   function updateTop { socket.emit("ain", ainNum); socket.emit("gpio", gpioNum); setTimeout(updateTop, updateTopInterval); }   //updateTop;

function updateBot { socket.emit("i2c", i2cNum); setTimeout(updateBot, updateBotInterval); }   //updateBot; });

Documents
SparkFun:_ITG-3200,Triple-Axis_Gyro

Schematic

Eagle Files

Quickstart Guide

ITG-3200 Datasheet

Code (ATmega328)

Example

Sparkfun

Github Repo