MSP430 硬件I2C ，时钟SCLK测量。

只看该作者 · 2013-2-21 19:07

大家好。。最近遇到MSP430硬件I2C通信问题，因而想测试一下I2C的SCLK信号。但是官网的I2C程序，在程序编译并写入MSP430F5438开发板之后。再用示波器一端接地一端接对应I2C的UCB0SCLK脚未测试到波形的存在。。因而想请教一下。这种测量方法是否正常呢。？？是否有其他测量方法呢。？硬件I2C通信时可以在开发板里面单步运行通信程序么。因为程序单步运行在发送数据的过程中会停留在等待发送区为空，但是全速运行时是不会有任何问题的。。

只看该作者 · 2013-2-21 19:07

我测试用的程序如下：

#include "msp430x54x.h"

unsigned char TXData;
unsigned char TXByteCtr;

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                // Stop WDT
  P11SEL |= BIT0 + BIT1 + BIT2;
  P11DIR |= BIT0 + BIT1 + BIT2;
  P3SEL |= 0x06;                         // 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.
//------------------------------------------------------------------------------
#pragma vector = USCI_B0_VECTOR
__interrupt void USCI_B0_ISR(void)
{
  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;
  }
}