5529 硬件I2C 无法进入中断

只看该作者 · 2015-3-31 14:07

本帖最后由 dingliangzhu 于 2015-3-31 15:31 编辑

#include <msp430.h>

unsigned char TXData;

unsigned char TXByteCtr;

int main(void)

{

  WDTCTL = WDTPW + WDTHOLD;                // Stop WDT

  P3SEL |= 0x03;                         // Assign I2C pins to USCI_B0

  UCB0CTL1 |= UCSWRST;                   // Enable SW reset

  UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC;    // I2C Master, synchronous mode

  UCB0CTL1 = UCSSEL_2 + UCSWRST;          // Use SMCLK, keep SW reset

  UCB0BR0 = 12;                            // fSCL = SMCLK/12 = ~100kHz

  UCB0BR1 = 0;

  UCB0I2CSA = 0x48;                      // Slave Address is 048h

  UCB0CTL1 &= ~UCSWRST;                   // Clear SW reset, resume operation

  UCB0IE |= UCTXIE;                      // Enable TX interrupt

  TXData = 0x01;                         // Holds TX data

  while (1)

  {

TXByteCtr = 1;                         // Load TX byte counter

while (UCB0CTL1 & UCTXSTP);          // Ensure stop condition got sent

UCB0CTL1 |= UCTR + UCTXSTT;          // I2C TX, start condition

__bis_SR_register(LPM0_bits + GIE);    // Enter LPM0 w/ interrupts

__no_operation();                      // Remain in LPM0 until all data

                                          // is TX'd



TXData++;                            // Increment data byte

  }

}

//------------------------------------------------------------------------------

// The USCIAB0_ISR is structured such that it can be used to transmit any

// number of bytes by pre-loading TXByteCtr with the byte count.

//------------------------------------------------------------------------------

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)

#pragma vector = USCI_B0_VECTOR

__interrupt void USCI_B0_ISR(void)

#elif defined(__GNUC__)

void __attribute__ ((interrupt(USCI_B0_VECTOR))) USCI_B0_ISR (void)

#else

#error Compiler not supported!

#endif

{

  switch(__even_in_range(UCB0IV,12))

  {

  case  0: break;                         // Vector  0: No interrupts

  case  2: break;                         // Vector  2: ALIFG

  case  4: break;                         // Vector  4: NACKIFG

  case  6: break;                         // Vector  6: STTIFG

  case  8: break;                         // Vector  8: STPIFG

  case 10: break;                         // Vector 10: RXIFG

  case 12:                               // Vector 12: TXIFG

if (TXByteCtr)                         // Check TX byte counter

{

   UCB0TXBUF = TXData;                // Load TX buffer

   TXByteCtr--;                         // Decrement TX byte counter

}

else

{

   UCB0CTL1 |= UCTXSTP;                // I2C stop condition

   UCB0IFG &= ~UCTXIFG;                // Clear USCI_B0 TX int flag

   __bic_SR_register_on_exit(LPM0_bits); // Exit LPM0

}

break;

  default: break;

  }

}

上面是TI官方提供的硬件I2C的一个操作例程。我将该例程下载到5528单片机中，调试中发现无法进入中断服务函数。我觉得执行完下面三句后，应该就要进入中断。

while (UCB0CTL1 & UCTXSTP);          // Ensure stop condition got sent

UCB0CTL1 |= UCTR + UCTXSTT;          // I2C TX, start condition

__bis_SR_register(LPM0_bits + GIE);    // Enter LPM0 w/ interrupts

其中， UCB0CTL1 |= UCTR + UCTXSTT;          // I2C TX, start condition  这条语句执行完后应该将起始位和从机地址发送出去，理论上在中断使能的情况下就可以进入中断了。

从机是PCF8574（i/o扩展芯片，用来驱动lcd1602），默认地址为0x27，从机地址是对的。上下拉电阻也加上了。不知道问题出在哪个方面，请大家帮帮忙，谢谢！