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/* compass.c
*
* Software to read from the CMPS03 magnetic compass.
*
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <linux/i2c-dev.h>
/* Note that the documentation for the compass states its address as 0xC0.
* However, this includes the low bit which specifies read or write.
* Linux i2c does not include this bit in this address, so the actual
* address is 0xC0 shifted down, 0x60.
*/
#define CMPS_Addr (0xC0>>1)
#define I2C_SLAVE 0x0B /* Change slave address
/* The important registers on the compass. Internal/test registers omitted. */
#define CMPS03_SOFTWARE_REVISION 0x0
#define CMPS03_BEARING_BYTE 0x1
#define CMPS03_BEARING_WORD_HIGH 0x2
#define CMPS03_BEARING_WORD_LOW 0x3
#define CMPS03_CALIBRATE_CMD 0xF
void I2C_addr (int Addr) // vybere adresu cidla se kterym se bude komunikovat
{
if (ioctl(file, I2C_SLAVE, Addr) == -1)
{
fprintf(stderr, "Failed to set address to 0x%02x.\n", Addr);
exit(-5);
}
}
int i2c_init() // zinicializuje i2c
{
file = open("/dev/i2c-0", O_RDWR);
if (file < 0)
{
cerr << "Could not open /dev/i2c-0." << endl;
return -1;
}
return 0;
}
unsigned char read_azimut_mag() // precte azimut z kompasu
{
char Buf[3]; // promena pro manipulaci s i2c
I2C_addr(CMPS_Addr);
Buf[0]=1;
write(file,Buf,1);
read(file, Buf,1);
return (Buf[0]-SEVER);
}
void calib() // kalibrace kompasu
{
char Buf[3]; // promena pro manipulaci s i2c
I2C_addr(CMPS_Addr);
Buf[0]=15;
Buf[1]=0xFF;
write(file,Buf,2);
}
int main(int argc, char *argv[])
{
char *end;
int res,file;
int error;
char filename[20] ;
long funcs;
int heading_byte, heading_word_h, heading_word_l;
int bearing_long, bearing_degrees;
sprintf(filename,"/dev/i2c-0");
file = open(filename,O_RDWR);
if (errno != 0)
{
switch (errno)
{
case EACCES:
fprintf(stderr,"Run as root? \n");
break;
default:
fprintf(stderr,"Error: Could not open file '%s' : %s \n", filename, strerror(errno));
break;
}
}
if (ioctl(file,I2C_SLAVE,CMPS03_ADDR) < 0) {
switch (errno)
{
case EBUSY:
printf("device is busy \n");
break;
default:
printf("Got error: %s \n", strerror(errno));
exit(0);
}
}
/* Get software revision number */
res = read(file, CMPS03_SOFTWARE_REVISION,1);
if (res < 0) {
printf("Cannot read software revision level \n");
} else {
printf("Software revision level: %02x \n", res);
}
/* Loop and read from the compass. */
while (1) {
/* The heading byte is 0-255 for the 360 degrees. */
heading_byte = read(file, CMPS03_BEARING_BYTE,1);
if (heading_byte < 0) { printf("Error reading from compass. \n"); exit(1);}
/* The high resolution heading is given in two registers, and is 10 * the
* heading in degrees, ie 359.9 degrees reads as 3599. */
heading_word_h = read(file, CMPS03_BEARING_WORD_HIGH,1);
if (heading_word_h < 0) { printf("Error reading from compass. \n"); exit(1);}
heading_word_l = read(file, CMPS03_BEARING_WORD_LOW,1);
if (heading_word_l < 0) { printf("Error reading from compass. \n"); exit(1);}
/* Combine the two bytes, and get the heading in degrees. */
bearing_long = heading_word_h * 256 + heading_word_l;
bearing_degrees = bearing_long / 10;
printf("Bearing: %d \n", bearing_degrees);
/* Wait for a while. */
usleep(200000);
}
}