ADS1248: Calibration

Hello,

I have installed the ADS1248 in my system as shown:

It is only used for reading voltages and temperatures via the internal sensor. Reading voltages works okay so far, the only problem is the self-calibration. Apparently it does not work, when I hard-code the offset register before (in this case for example with 0x02, just to check if it is changing):

 #define SELFOCAL 0x62

write_register(fd, OFC0, 0x02);	
write_register(fd, OFC1, 0x02);	
write_register(fd, OFC2, 0x02);	

self_off_calibration(fd, sps); 

printf("OFC0_after_cal: %02x\n",read_register(fd, OFC0)); 
printf("OFC1_after_cal: %02x\n",read_register(fd, OFC1)); 
printf("OFC2_after_cal: %02x\n",read_register(fd, OFC2)); 

static void self_off_calibration(int fd, uint32_t sps) { 
        uint8_t tx[] = {SELFOCAL, };
        spitransfer(fd, tx, NULL); 
        time_filter(sps, 'c'); 

}

static void write_register(int fd, uint8_t addr, uint8_t value)
{
	uint8_t tx[] = {WREG|addr, 0x00, value, };
	
	spitransfer(fd, tx, NULL);
}

static uint8_t read_register(int fd, uint8_t addr)
{
	uint8_t tx[] = {RREG|addr, 0x00, NOP};
	uint8_t rx[] = {0xFE, 0XFE, 0xFE};
	uint8_t hex;
	int i;

	spitransfer(fd, tx, rx);
	hex = rx[2];
	return hex;
}

time_filter is just a delay function.

The output of the offset registers stays always 0x02, even though it should have been over-written.

Did I maybe forget anything regarding the self-calibration?

Thanks in advance,

Lukas