[En-Nut-Discussion] TWI Initialisation

[Peter Sodermanns]

Hi group,

I'm trying to get TWI working on an Ethernut 2.1B but till now with no 
success.
Initialisation of TWI seems to fail, I never get any signal on Port 
D0/D1 (=SCL/SDA).
Hardware malfunction is unlikely, I tried 2 different Ethernuts, each 
with just 1k5 pull up resistors on D0/D1.

My program is stripped down to the minimum and uses only twif.c:


#include <stdio.h>
#include <io.h>
#include <sys/version.h>
#include <sys/event.h>
#include <sys/timer.h>
#include <sys/heap.h>
#include <dev/debug.h>
#include <dev/twif.h>

int main(void)
{
u_long baud0 = 19200;
u_long TWI_speed;
int result = 0;

	NutRegisterDevice(&devDebug0, 0, 0);
	freopen("uart0", "w", stdout);
	_ioctl(_fileno(stdout), UART_SETSPEED, &baud0);
	NutSleep(200);

	printf_P(PSTR("\n\n\n"));
	printf_P(PSTR("Nut/OS:       %s\n"), NutVersionString());

	for (;;) {

		printf_P(PSTR(" TWBR = %d\n"), TWBR);
		printf_P(PSTR(" TWCR = %d\n"), TWCR);
		printf_P(PSTR(" TWDR = %d\n"), TWDR);
		printf_P(PSTR(" TWAR = %d\n"), TWAR);
		printf_P(PSTR(" TWSR = %d\n"), TWSR);

		result = TwInit(1);
		printf_P(PSTR("TwInit MasterError = %d, result = %d\n"), 
TwMasterError(), result);
		printf_P(PSTR(" TWBR = %d\n"), TWBR);
		printf_P(PSTR(" TWCR = %d\n"), TWCR);
		printf_P(PSTR(" TWDR = %d\n"), TWDR);
		printf_P(PSTR(" TWAR = %d\n"), TWAR);
		printf_P(PSTR(" TWSR = %d\n"), TWSR);

		TWI_speed = 10000;
		result = TwIOCtl(TWI_SETSPEED, &TWI_speed);
		printf_P(PSTR("TWI_SETSPEED MasterError = %d, result = %d\n"), 
TwMasterError(), result);
		printf_P(PSTR(" TWBR = %d\n"), TWBR);
		printf_P(PSTR(" TWCR = %d\n"), TWCR);
		printf_P(PSTR(" TWDR = %d\n"), TWDR);
		printf_P(PSTR(" TWAR = %d\n"), TWAR);
		printf_P(PSTR(" TWSR = %d\n"), TWSR);

		while(1);
	}
}


The resulting debug output is:

Nut/OS:       3.9.7.1
  TWBR = 0
  TWCR = 0
  TWDR = 255
  TWAR = 254
  TWSR = 248
TwInit MasterError = 0, result = 0
  TWBR = 191
  TWCR = 5
  TWDR = 255
  TWAR = 3
  TWSR = 250
TWI_SETSPEED MasterError = 0, result = 0
  TWBR = 182
  TWCR = 5
  TWDR = 255
  TWAR = 3
  TWSR = 249


Problem:

TWINT in register TWCR is not set,
interrupt routine is never executed,
no signals at output pins.


Any ideas what the cause could be?



Many Thanks,

                   Peter