Subversion Repositories svnkaklik

Rev

Details | Last modification | View Log

Rev Author Line No. Line
354 kaklik 1
/* compass.c
2
 *
3
 * Software to read from the CMPS03 magnetic compass. 
4
 *
5
 * By Josh Marshall, joshua dot marshall at studentmail dot newcastle dot edu dot au
6
 * October 15, 2004.
7
 *
8
 * Adapted from code for the SP03 speech synthesiser 
9
 * By Bram Stolk, b.stolk at chello.nl
10
 *
11
 * Bram Stolk's notes:
12
 * In linux, you can do I2C stuff in user-space, if you enable
13
 * the device-interface to i2c. You can use plain read() and 
14
 * write() calls on your /dev/i2c-0 file.
15
 *
16
 * NOTE: Check if you have an i2c adapter active by doing:
17
 * cat /proc/bus/i2c
18
 * If this comes up empty, then you have no adapters. If the
19
 * file does not exist at all, you probably lack i2c kernel
20
 * support alltogether.
21
 */
22
 
23
#include <errno.h>
24
#include <string.h>
25
#include <stdio.h>
26
#include <stdlib.h>
27
#include <unistd.h>
28
#include <fcntl.h>
29
#include <linux/i2c-dev.h>
30
 
31
/* Note that the documentation for the compass states its address as 0xC0.
32
 * However, this includes the low bit which specifies read or write.
33
 * Linux i2c does not include this bit in this address, so the actual
34
 * address is 0xC0 shifted down, 0x60.
35
 */
36
#define CMPS03_ADDR 0x60
37
 
38
/* The important registers on the compass. Internal/test registers omitted. */
39
#define CMPS03_SOFTWARE_REVISION 0x0
40
#define CMPS03_BEARING_BYTE 0x1
41
#define CMPS03_BEARING_WORD_HIGH 0x2
42
#define CMPS03_BEARING_WORD_LOW 0x3
43
#define CMPS03_CALIBRATE_CMD 0xF
44
 
45
int main(int argc, char *argv[]) {
46
   char *end;
47
   int res,file;
48
   int e1;
49
   char filename[20] ;
50
   long funcs;
51
 
52
   int heading_byte, heading_word_h, heading_word_l;
53
   int bearing_long, bearing_degrees;
54
 
55
   sprintf(filename,"/dev/i2c-%d");
56
   if ((file = open(filename,O_RDWR)) < 0) {
57
     e1 = errno;
58
     if (e1 != ENOENT) {
59
       fprintf(stderr,"Error: Could not open file '%s' : %sn",
60
               filename,strerror(e1));
61
       if(e1 == EACCES)
62
         fprintf(stderr,"Run as root?n");
63
     }
64
   } 
65
 
66
   if (ioctl(file,I2C_SLAVE,CMPS03_ADDR) < 0) {
67
     if (errno == EBUSY) {
68
       printf("device is busyn");
69
     }
70
     printf("Got error: %d\n", errno);
71
     exit(0);
72
   }
73
 
74
   /* Get software revision number */
75
   res = i2c_smbus_read_byte_data(file, CMPS03_SOFTWARE_REVISION);
76
   if (res < 0) {
77
     printf("Cannot read software revision leveln");
78
   } else {
79
     printf("Software revision level: %02xn", res);
80
   }
81
 
82
   /* Loop and read from the compass. */
83
   while (1) {
84
     /* The heading byte is 0-255 for the 360 degrees. */
85
     heading_byte = i2c_smbus_read_byte_data(file, CMPS03_BEARING_BYTE);
86
     if (heading_byte < 0) { printf("Error reading from compass."); exit(1);}
87
 
88
     /* The high resolution heading is given in two registers, and is 10 * the 
89
      * heading in degrees, ie 359.9 degrees reads as 3599. */
90
     heading_word_h = i2c_smbus_read_byte_data(file, CMPS03_BEARING_WORD_HIGH);
91
     if (heading_word_h < 0) { printf("Error reading from compass."); exit(1);}
92
     heading_word_l = i2c_smbus_read_byte_data(file, CMPS03_BEARING_WORD_LOW);
93
     if (heading_word_l < 0) { printf("Error reading from compass."); exit(1);}
94
 
95
     /* Combine the two bytes, and get the heading in degrees. */
96
     bearing_long = heading_word_h * 256 + heading_word_l;
97
     bearing_degrees = bearing_long / 10;
98
 
99
     printf("Bearing: %d \n", bearing_degrees);
100
 
101
     /* Wait for a while. */
102
     usleep(200000);
103
   }
104
}