I would like to configure a Hall effect sensor with I2C but I don't really see how to manage it. I don't really know which value that I have to enter in each registers, but this not the biggest issue. Indeed i would like to read the registers in order to modify them to have an idea of what i could change.
To do so i wrote 2 programms, respectively to write/read into registers. But i'm far from being an expert and i would't like some recommandations and advice on how i could change my code in order to make it work properly.
includes for both files
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/i2c-dev.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <stdint.h>
Write :
int file_i2c;
uint8_t buffer[2] = { 0 };
int addr = 0x31;
char *end;
char buf[12];
int main(void)
{
//----- OPEN THE I2C BUS -----
char *filename = (char *)"/dev/i2c-1";
if ((file_i2c = open(filename, O_RDWR)) < 0)
{
return EXIT_FAILURE;
}
if (ioctl(file_i2c, I2C_SLAVE, addr) < 0)
{
return EXIT_FAILURE;
}
int length = 0;
for( int i = 0xC0 ; i<0xE5 ; i++)
{
if( i < 0xD1 || i > 0xE0)
{
buffer[0] = i;
printf("Rgister value for 0x%02X : ",buffer[0]);
do {
if (!fgets(buf, sizeof buf, stdin))
break;
// remove \n
buf[strlen(buf) - 1] = 0;
buffer[1] = strtol(buf, &end, 2);
} while (end != buf + strlen(buf));
printf("\n");
length = 2;
if (write(file_i2c, buffer, length) != length)
{
printf("Failed to write to the i2c bus.\n");
}
}
}
close(file_i2c);
return EXIT_SUCCESS;
}
Read :
int file_i2c;
int addr = 0x31;
int main(void)
{
//----- OPEN THE I2C BUS -----
char *filename = (char *)"/dev/i2c-1";
if ((file_i2c = open(filename, O_RDWR)) < 0)
{
return EXIT_FAILURE;
}
if (ioctl(file_i2c, I2C_SLAVE, addr) < 0)
{
return EXIT_FAILURE;
}
uint8_t register_addr;
uint8_t str;
for( int i = 0xC0 ; i<0xE5 ; i++)
{
if( i < 0xD1 || i > 0xE0)
{
register_addr = i >> 8;
if(write(file_i2c, ®ister_addr, 1) == 1)
{
if (read(file_i2c, &str, 1) != 1)
{
fprintf(stderr,"Failed to read\n");
}
else
{
printf("data on 0x%02X : 0x%02X\n",i,str);
}
}
}
}
close(file_i2c);
return EXIT_SUCCESS;
}
we cannot know if the writing program works because the reading program returns
data on 0xC0 : 0x00
data on 0xC1 : 0x00
data on 0xC2 : 0x00
data on 0xC3 : 0x00
data on 0xC4 : 0x00
data on 0xC5 : 0x00
data on 0xC6 : 0x00
data on 0xC7 : 0x00
data on 0xC8 : 0x00
data on 0xC9 : 0x00
data on 0xCA : 0x00
data on 0xCB : 0x00
data on 0xCC : 0x00
data on 0xCD : 0x00
data on 0xCE : 0x00
data on 0xCF : 0x00
data on 0xD0 : 0x00
data on 0xE1 : 0x00
data on 0xE2 : 0x00
data on 0xE3 : 0x00
data on 0xE4 : 0x00
I hope you'll be able to help, thanks a lot, yocvito
Finally, the reading program works perfectly.
there was just a problem on that line.
register_addr = i >> 8;
I shifted right by 8 bits without really knowing why
so I replaced this line with
register_addr = i;
And so I have the expected return (the values correspond to those expected)
data on 0xC0 : 0x14
data on 0xC1 : 0x00
data on 0xC2 : 0x00
data on 0xC3 : 0x00
data on 0xC4 : 0x02
data on 0xC5 : 0x00
data on 0xC6 : 0xB0
data on 0xC7 : 0x12
data on 0xC8 : 0xE6
data on 0xC9 : 0xBD
data on 0xCA : 0xD1
data on 0xCB : 0x58
data on 0xCC : 0xB9
data on 0xCD : 0x00
data on 0xCE : 0x05
data on 0xCF : 0x33
data on 0xD0 : 0x00
data on 0xE1 : 0x00
data on 0xE2 : 0x00
data on 0xE3 : 0x00
data on 0xE4 : 0x00
As for the writing program, it was already working (he wrote well in the registers indicated). But, the written values are wrong (except for the first register).
Write :
Valeur de registre pour 0xC0 : 00010100
Valeur de registre pour 0xC1 : 11111111
Valeur de registre pour 0xC2 : 11111111
Read :
data on 0xC0 : 0x14
data on 0xC1 : 0x7F
data on 0xC2 : 0x1F
Do you have any idea where this might come from?