MSP430G系列使用硬件IIC还需不需要外部接上拉电阻？

lingming zhang 说：

难受，我边看寄存器边调试，发现产生一个开始信号之后，UCTXSTT这个为就一直是1，表面从机没给应答，不知道怎么回事，从机应该不会出错，毕竟模拟IIC就是这个地址，无奈，希望大家给点意见，感谢！

你是不是用Launchpad调的？ Launchpad 上P1.6接着一个LED，你需要把跳帽拔掉

#include <msp430.h>

unsigned char TXData[3]={0x01,0b10000100,0b10000011};
unsigned char TXByteCtr;

int main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  P1SEL |= BIT6 + BIT7;                     // Assign I2C pins to USCI_B0
  P1SEL2|= BIT6 + BIT7;                     // 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
  IE2 |= UCB0TXIE;                          // Enable TX interrupt



  TXByteCtr = 1;                          // Load TX byte counter
  __bis_SR_register(GIE);        // Enter LPM0 w/ interrupts


   while (UCB0CTL1 & UCTXSTP);             // Ensure stop condition got sent
   UCB0CTL1 |= UCTR + UCTXSTT;             // I2C TX, start condition


}

//------------------------------------------------------------------------------
// The USCIAB0TX_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 = USCIAB0TX_VECTOR
__interrupt void USCIAB0TX_ISR(void)
{
  if (TXByteCtr==1)                            // Check TX byte counter
  {
	  UCB0TXBUF = TXData[0];                     // Load TX buffer
	  UCB0TXBUF = TXData[1];                     // Load TX buffer
	  UCB0TXBUF = TXData[2];                     // Load TX buffer
	  TXByteCtr--;
  }
  if(TXByteCtr==0)
  {
    UCB0CTL1 |= UCTXSTP;                    // I2C stop condition
    IFG2 &= ~UCB0TXIFG;                     // Clear USCI_B0 TX int flag
   // __bic_SR_register_on_exit(CPUOFF);      // Exit LPM0
  }
}