SparkFun: ITG-3200,Triple-Axis Gyro Display
Embedded Linux Class Ruffin White RHIT
Contents
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.
Code
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.
/*
* MiniProject02.c
*
* Created on: Sep 20, 2012
* Author: Ruffin White
*/
#include "Header.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <poll.h>
#include <signal.h>
#include "ITG-3200.h"
int loop=1;
void signal_handler(int sig)
{
printf( "Ctrl-C pressed, cleaning up and exiting..\n" );
loop = 0;
}
int main(int argc, char** argv){
//variable declarations
struct pollfd fdset[1];
int nfds = 1;
int timeout = 100;
int rc;
char* buf[MAX_BUF];
int gpio1, gpio2;
int gpio1_fd, gpio2_fd;
int gpio2_value = 0;
int pattern =0;
int value =0;
int freq = 10;
int duty = 25;
short int gyroID, gyroTemp, gyroX, gyroY, gyroZ;
// I2C Variables
char *end;
int res, i2cbus, address, size, file;
int daddress;
//check that at least two arguments are passed in
if(argc < 4){
printf("Usage: %s <input-gpio> <output-gpio> <i2c-bus>\n", argv[0]);
printf("polls input-gpio, and writes value to output-gpio\n");
fflush(stdout);
return 1;
}
//set signal handler for Ctrl + C
if (signal(SIGINT, signal_handler) == SIG_ERR)
printf("\ncan't catch SIGINT\n");
//assign gpio values
gpio1 = atoi(argv[1]);
gpio2 = atoi(argv[2]);
//assign I2C values
i2cbus = atoi(argv[3]);
address = ITG3200_I2C_ADDRESS;
file = initialize(i2cbus, address);
zeroGyro(file);
//argument 1 will be input
export_gpio(gpio1);
set_gpio_direction(gpio1, "in");
set_gpio_edge(gpio1, "falling");
gpio1_fd = gpio_fd_open(gpio1);
//argument 2 will be output
export_gpio(gpio2);
set_gpio_direction(gpio2, "out");
set_gpio_value(gpio2, gpio2_value);
gpio2_fd = gpio_fd_open(gpio2);
set_mux_value("gpmc_a2",6);
while(loop){
memset((void*)fdset, 0, sizeof(fdset));
fdset[0].fd = gpio1_fd;
fdset[0].events = POLLPRI;
rc = poll(fdset, nfds, timeout);
if (rc < 0){
printf("\npoll() failed!\n");
}
if (rc == 0){
printf(".");
}
if((fdset[0].revents & POLLPRI) == POLLPRI) {
read(fdset[0].fd, buf, MAX_BUF);
printf("interrupt value=%c\n", buf[0]);
pattern++;
if(pattern == 4){
pattern = 0;
}
}
switch(pattern){
// blink led
case 0:
printf("Case 0\n");
value = read_ain("ain6");
printf("Voltage: %d\n",value);
set_pwm("ehrpwm.1:0",10,25);
if(gpio2_value){
gpio2_value = 0;
}
else{
gpio2_value = 1;
}
set_gpio_value(gpio2, gpio2_value);
break;
//PWM output
case 1:
printf("Case 1\n");
gyroID = readWhoAmI(file);
printf("gyroID: %6d\n", gyroID);
break;
//Read Gyro Temperature
case 2:
printf("Case 2\n");
gyroTemp = readTemp(file);
printf("gyroTemp: %6d\n", gyroTemp);
break;
//Read Gyro XYZ
case 3:
printf("Case 3\n");
gyroX = readX(file);
gyroY = readY(file);
gyroZ = readZ(file);
printf("gyroX: %6d\n", gyroX);
printf("gyroY: %6d\n", gyroY);
printf("gyroZ: %6d\n", gyroZ);
break;
default:
break;
}
}
close(file);
gpio_fd_close(gpio1_fd);
gpio_fd_close(gpio2_fd);
unexport_gpio(gpio1);
unexport_gpio(gpio2);
fflush(stdout);
return 0;
}
Screen Shots
Features
Digital-output X-, Y-, and Z-Axis angular rate sensors (gyros) on one integrated circuit Digitally-programmable low-pass filter Low 6.5mA operating current consumption for long battery life Wide VDD supply voltage range of 2.1V to 3.6V Standby current: 5μA Digital-output temperature sensor Fast Mode I2C (400kHz) serial interface Optional external clock inputs of 32.768kHz or 19.2MHz to synchronize with system clock Pins broken out to a breadboard friendly 7-pin 0.1" pitch header
Documents
SparkFun:_ITG-3200,Triple-Axis_Gyro
Embedded Linux Class Ruffin White RHIT
