I2C problems

schneiderham posted on 3 Nov 2009 10:15 PM

rated by 0 users

Hi,

I am using a MSP430F5419 and a BQ272000 Battery fuel gauge using I2C.  I seem to be having troubles reliably communicating.  About 50% of the I2C interactions result in no acks; more specifically, it usually gets stuck in line (5) waiting for UCTXIFG.

Here is some simple code to read a register.  Note that the TimerWatchDog is used to avoid infinite loops.

1: SysTickStartTimer(&TimerWatchDog, 2);

2: while (UCB2CTL1 & UCTXSTP && !(SYSTICK_TIMER_ELAPSED(&TimerWatchDog)));             // Ensure last stop condition got sent

3:  UCB2CTL1 |= UCTR;

 4:  UCB2CTL1 |= UCTXSTT;             // I2C TX, start condition  

 5:  while (!(UCB2IFG & UCTXIFG) && !(SYSTICK_TIMER_ELAPSED(&TimerWatchDog)));           // When UCTXIFG is set the Start has been sent  

  6: UCB2TXBUF = Cmd;                        // Write Cmd  

  7: while (!(UCB2IFG & UCTXIFG) && !(SYSTICK_TIMER_ELAPSED(&TimerWatchDog)));           // Ensure Cmd is being sent  

  // Gointo Rx Mode

  8: UCB2CTL1 &= ~UCTR;

  9: UCB2CTL1 |= UCTXSTT;             // I2C RX, start condition

  10: while (UCB2CTL1 & UCTXSTT && !(SYSTICK_TIMER_ELAPSED(&TimerWatchDog)));             // Ensure start and address got sent

  11: UCB2CTL1 |= UCTXSTP;                // Generate I2C stop condition

  12: while (!(UCB2IFG & UCRXIFG) && !(SYSTICK_TIMER_ELAPSED(&TimerWatchDog)));           // Ensure Data Sent

  13: *Data = UCB2RXBUF;  

  14: __delay_cycles(I2C_ACCESS_DELAY*20);

  if( SYSTICK_TIMER_ELAPSED(&TimerWatchDog) )

  {

    return FALSE;

  }

  else

  {

    return TRUE;

  }

ANy suggestions.