【求助】关于MSP430通过硬件I2C接口连接从器件ADT7420的问题

 #include <msp430.h>

    unsigned char *PRxData;                     // Pointer to RX data
    unsigned char RXByteCtr;
    volatile unsigned char RxBuffer[128];       // Allocate 128 byte of RAM

    int main(void)
    {
      WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
      P4SEL|=BIT1+BIT2;                             // Assign I2C pins to USCI_B1
      UCB1CTL1 |= UCSWRST;                      // Enable SW reset
      UCB1CTL0 = UCMST + UCMODE_3 + UCSYNC;     // I2C Master, synchronous mode
      UCB1CTL1 = UCSSEL_2 + UCSWRST;            // Use SMCLK, keep SW reset
      UCB1BR0 = 12;                             // fSCL = SMCLK/12 = ~100kHz
      UCB1BR1 = 0;
      UCB1I2CSA = 0x49;                         // Slave Address is 048h
      UCB1CTL1 &= ~UCSWRST;                     // Clear SW reset, resume operation
      UCB1IE |= UCRXIE;                         // Enable RX interrupt

      while (1)
      {
        PRxData = (unsigned char *)RxBuffer;    // Start of RX buffer
        RXByteCtr = 5;                          // Load RX byte counter
        while (UCB1CTL1 & UCTXSTP);             // Ensure stop condition got sent
        UCB1CTL1 |= UCTXSTT;                    // I2C start condition

        __bis_SR_register(LPM0_bits + GIE);     // Enter LPM0, enable interrupts
                                                // Remain in LPM0 until all data
                                                // is RX'd
        __no_operation();                       // Set breakpoint >>here<< and
      }                                         // read out the RxBuffer buffer
    }

    //-------------------------------------------------------------------------------
    // The USCI_B0 data ISR is used to move received data from the I2C slave
    // to the MSP430 memory. It is structured such that it can be used to receive
    // any 2+ number of bytes by pre-loading RXByteCtr with the byte count.
    //-------------------------------------------------------------------------------
    #pragma vector = USCI_B1_VECTOR
    __interrupt void USCI_B1_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:                                  // Vector 10: RXIFG
        RXByteCtr--;                            // Decrement RX byte counter
        if (RXByteCtr)
        {
          *PRxData++ = UCB1RXBUF;               // Move RX data to address PRxData
          if (RXByteCtr == 1)                   // Only one byte left?
            UCB1CTL1 |= UCTXSTP;                // Generate I2C stop condition
        }
        else
        {
          *PRxData = UCB1RXBUF;                 // Move
        }
      }
    }

上拉电阻太大了一点，你改成1.5k或者2.2k试试

换了电阻了，但是问题还是没有解决，依旧没有时钟信号

这问题我也遇到过，你是不是上拉的电压太高或者不够？看看器件规格书，有的器件上拉电压不能高于VDDIO以上一定电压。

还有有可能干扰问题？买个协议分析仪吧，记得买贵点的，否则杂波很多。