SparkFun: ITG-3200,Triple-Axis Gyro

Overview
The ITG-3200 is a three-axis gyro that can be purchased from SparkFun. The datasheet describes it:

''The ITG-3200 is the world’s first single-chip, digital-output, 3-axis MEMS gyro IC optimized for gaming, 3D mice, and 3D remote control applications. The part features enhanced bias and sensitivity temperature stability, reducing the need for user calibration. Low frequency noise is lower than previous generation devices, simplifying application development and making for more-responsive remote controls.''



Inputs and Outputs
The ITG-3200 takes a supply voltage (Vs) of 1.8-3.6 V. The analog outputs are scaled proportionally to the supply voltage; at Vs = 3.6 V, the output will change by 2x for the same acceleration as compared to Vs = 1.8 V. Although the output sensitivity is scaled proportionally to the input voltage, noise is not, so higher supply voltages are advisable to reduce the impact of noise.

At all supply voltages, 0 g acceleration corresponds to an output voltage of Vs/2. At Vs = 3.6 V, the datasheet specs the typical sensitivity at 360 mV / g, with g as standard gravitational acceleration.



Connecting to the Bone
The Beagle Bone can be connected to the gyro via the I2C bus. Ground and Vcc on the breakout board should be connected to pins 1 and 2 respectively on the bone's P9 header, and the SCL and SDA pins should be connected to one of the I2C pairs on the bone. VIO should also be simply tied to Vcc, as this will be the same voltage the bone will use when acting as the master in the I2C buss. CLK should also be tied to ground unless you plan to use your own clock, grounding CLK will simply allow the device to use its own internal oscillator. Two 4.7k resistors should used be connected between SCL and then Vcc and between SDA and Vcc. There are available resistor pads on the breakout board I you prefer to have surface mounts on the board instead of bread boarding them. I used I2C3 (P9, pins 19 and 20). The address of the magnetometer can be found by using the i2cdetect command from the shell. I get:

beagle$ i2cdetect -y -r 3 0 1  2  3  4  5  6  7  8  9  a  b  c  d  e  f 00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 10: -- -- -- -- -- -- -- -- -- -- -- UU -- -- -- -- 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --  40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --  50: -- -- -- -- UU UU UU UU -- -- -- -- -- -- -- -- 60: -- -- -- -- -- -- -- -- -- 69 -- -- -- -- -- -- 70: -- -- -- -- -- -- -- --

The address should be 0x69 (or 105 in decimal). This address can be changed by soldering an arrangement of resistors on the reserved pads on the breakout board.

Registers
the ITG-3200 has 14 8-bit registers:

The sensor values for each axis are 16-bit and are stored across 2 registers each. GYRO_#OUT_H and GYRO_#OUT_L where # is just letter for the axis. Will have to get the two halves of the 16-bit signed measurement to read the entire value..

Sample C Code
The code shown below is sample code to demonstrate reading the registers via I2C and using the library.Specifically the code sets up some peripherals like buttons and interrupts and the I2C buss. The code will also zero out the gyro to account for the internal bias the gyro might have just being stationary and level. Then with by pressing the button the code will toggle through and repetitively read different poll the gyro and print and display the results to the terminal. Simply press ‘CTRL’ + ‘C’ to quit the program.

/* * MiniProject02.c * * Created on: Sep 20, 2012 *     Author: Ruffin White */


 * 1) include "Header.h"
 * 2) include 
 * 3) include 
 * 4) include 
 * 5) include 
 * 6) include 
 * 7) include 
 * 8) include 
 * 9) 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   \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; }

Header File
The code shown below is header file code used for using the gyro. This header file contains all the read and write functions to access all the applicable registers via I2C that exist on the Gyro. See the data sheet for more detail on what each register is for.

/* * ITG3200.h * * Created on: Sep 20, 2012 *     Author: Ruffin White */

/** * Includes */
 * 1) include 
 * 2) include "i2c-dev.h"

/** * Defines */
 * 1) define ITG3200_I2C_ADDRESS 0x69 //7-bit address that Gyro is originally configured by the break-out board

//--- // Registers //---
 * 1) define WHO_AM_I_REG   0x00
 * 2) define SMPLRT_DIV_REG 0x15
 * 3) define DLPF_FS_REG    0x16
 * 4) define INT_CFG_REG    0x17
 * 5) define INT_STATUS     0x1A
 * 6) define TEMP_OUT_H_REG 0x1B
 * 7) define TEMP_OUT_L_REG 0x1C
 * 8) define GYRO_XOUT_H_REG 0x1D
 * 9) define GYRO_XOUT_L_REG 0x1E
 * 10) define GYRO_YOUT_H_REG 0x1F
 * 11) define GYRO_YOUT_L_REG 0x20
 * 12) define GYRO_ZOUT_H_REG 0x21
 * 13) define GYRO_ZOUT_L_REG 0x22
 * 14) define PWR_MGM_REG    0x3E

// // Low Pass Filter Bandwidths //
 * 1) define LPFBW_256HZ 0x00
 * 2) define LPFBW_188HZ 0x01
 * 3) define LPFBW_98HZ 0x02
 * 4) define LPFBW_42HZ 0x03
 * 5) define LPFBW_20HZ 0x04
 * 6) define LPFBW_10HZ 0x05
 * 7) define LPFBW_5HZ  0x06

//--- // Offsets //--- short int TEMP_OUT_OFFSET = 0; short int GYRO_XOUT_OFFSET = 0; short int GYRO_YOUT_OFFSET = 0; short int GYRO_ZOUT_OFFSET = 0;

// // Read Functions //

//This function is used to initialize the gyroscope. The function returns the -errno if an error accrues. short int initialize(int i2cbus, int address){

char filename[20]; int file; sprintf(filename, "/dev/i2c-%d", i2cbus); file = open(filename, O_RDWR); if (file<0) { return -errno; }

if (ioctl(file, I2C_SLAVE, address) < 0) { return -errno; }	return file;

}

//This function is used to initialize the gyroscope. The function returns the -errno if an error accrues. short int zeroGyro(int file){

GYRO_XOUT_OFFSET = readX(file); GYRO_YOUT_OFFSET = readY(file); GYRO_ZOUT_OFFSET = readZ(file);

}

//This function is used to read the WHO_AM_I_REG of the gyroscope. //Usage: int gyroID = readWhoAmI; short int readWhoAmI(int file) { short int data=0; data = i2c_smbus_read_byte_data(file, WHO_AM_I_REG);

return data; }

//This function is used to write the WHO_AM_I_REG of the gyroscope. //Usage: data = readWhoAmI(data); short int writeWhoAmI(int file, short int data) { i2c_smbus_write_byte_data(file,WHO_AM_I_REG,data);

return data; }

//This function is used to read the SMPLRT_DIV_REG of the gyroscope. short int readSmplrtDiv(int file) { short int data=0; data = i2c_smbus_read_byte_data(file, SMPLRT_DIV_REG);

return data; }

//This function is used to write the SMPLRT_DIV_REG of the gyroscope. short int writeSmplrtDiv(int file, short int data) { i2c_smbus_write_byte_data(file,SMPLRT_DIV_REG,data);

return data; }

//This function is used to read the DLPF_FS_REG of the gyroscope. short int readDlpfFs(int file) { short int data=0; data = i2c_smbus_read_byte_data(file, DLPF_FS_REG);

return data; }

//This function is used to write the DLPF_FS_REG of the gyroscope. short int writeDlpfFs(int file, short int data) { i2c_smbus_write_byte_data(file,DLPF_FS_REG,data);

return data; }

//This function is used to read the INT_CFG_REG of the gyroscope. short int readIntCfg(int file) { short int data=0; data = i2c_smbus_read_byte_data(file, INT_CFG_REG);

return data; }

//This function is used to write the INT_CFG_REG of the gyroscope. short int writeIntCfg(int file, short int data) { i2c_smbus_write_byte_data(file,INT_CFG_REG,data);

return data; }

//This function is used to read the INT_STATUS of the gyroscope. short int readIntStatus(int file) { short int data=0; data = i2c_smbus_read_byte_data(file, INT_STATUS);

return data; }

//This function is used to read the temperature of the gyroscope. //Usage: int gyroTemp = readTemp; short int readTemp(int file) { short int data=0; data = i2c_smbus_read_byte_data(file, TEMP_OUT_H_REG)<<8; data |= i2c_smbus_read_byte_data(file, TEMP_OUT_L_REG);

return data; }

//This function is used to read the X-Axis rate of the gyroscope. The function returns the ADC value from the Gyroscope //NOTE: This value is NOT in degrees per second. //Usage: int xRate = readX; short int readX(int file) { short int data=0; data = i2c_smbus_read_byte_data(file, GYRO_XOUT_H_REG)<<8; data |= i2c_smbus_read_byte_data(file, GYRO_XOUT_L_REG);

return data - GYRO_XOUT_OFFSET; }

//This function is used to read the Y-Axis rate of the gyroscope. The function returns the ADC value from the Gyroscope //NOTE: This value is NOT in degrees per second. //Usage: int yRate = readY; short int readY(int file) { short int data=0; data = i2c_smbus_read_byte_data(file, GYRO_YOUT_H_REG)<<8; data |= i2c_smbus_read_byte_data(file, GYRO_YOUT_L_REG);

return data - GYRO_YOUT_OFFSET; }

//This function is used to read the Z-Axis rate of the gyroscope. The function returns the ADC value from the Gyroscope //NOTE: This value is NOT in degrees per second. //Usage: int zRate = readZ; short int readZ(int file) { short int data=0; data = i2c_smbus_read_byte_data(file, GYRO_ZOUT_H_REG)<<8; data |= i2c_smbus_read_byte_data(file, GYRO_ZOUT_L_REG);

return data - GYRO_ZOUT_OFFSET; }

//This function is used to read the PWR_MGM_REG of the gyroscope. short int readPwrMgm(int file) { short int data=0; data = i2c_smbus_read_byte_data(file, PWR_MGM_REG);

return data; }

//This function is used to write the PWR_MGM_REG of the gyroscope. short int writePwrMgm(int file, short int data) { i2c_smbus_write_byte_data(file,PWR_MGM_REG,data);

return data; }

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

Dimensions
0.70 x 0.55" (17.78 x 13.97mm)

Documents
Schematic

Eagle Files

Quickstart Guide

ITG-3200 Datasheet

Code (ATmega328)

Example

Sparkfun