MSP430F149使用P6口采集外部电压时受IO口电压影响，怎么解决？？

void Port_Init()
{
P6DIR = 0x00; //设置IO口方向为输入
P6OUT = 0xFF; //P6口初始设置为FF
}

这是我对P6口的初试。电路的话使用的是开发板，将输出为0-3V左右的太阳能电池板的正负极直接接入P6.0口和地来进行电压采集。

这样配置是有问题的，建议参考官网的例程。

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//******************************************************************************
//  MSP-FET430P140 Demo - ADC12, Sample A0, Set P1.0 if A0 > 0.5*AVcc
//
//  Description: A single sample is made on A0 with reference to AVcc.
//  Software sets ADC10SC to start sample and conversion - ADC12SC
//  automatically cleared at EOC. ADC12 internal oscillator times sample (16x)
//  and conversion. In Mainloop MSP430 waits in LPM0 to save power until ADC12
//  conversion complete, ADC12_ISR will force exit from LPM0 in Mainloop on
//  reti. If A0 > 0.5*AVcc, P1.0 set, else reset.
//
//                MSP430F149
//             -----------------
//         /|\|              XIN|-
//          | |                 |
//          --|RST          XOUT|-
//            |                 |
//      Vin-->|P6.0/A0      P1.0|--> LED
//
//  M. Buccini
//  Texas Instruments Inc.
//  Feb 2005
//  Built with CCE Version: 3.2.0 and IAR Embedded Workbench Version: 3.21A
//******************************************************************************

#include <msp430.h>

int main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  ADC12CTL0 = SHT0_2 + ADC12ON;             // Set sampling time, turn on ADC12
  ADC12CTL1 = SHP;                          // Use sampling timer
  ADC12IE = 0x01;                           // Enable interrupt
  ADC12CTL0 |= ENC;                         // Conversion enabled
  P6SEL |= 0x01;                            // P6.0 ADC option select
  P1DIR |= 0x01;                            // P1.0 output

  for (;;)
  {
    ADC12CTL0 |= ADC12SC;                   // Sampling open
    __bis_SR_register(CPUOFF + GIE);        // LPM0, ADC12_ISR will force exit
  }
}

// ADC12 interrupt service routine
#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=ADC12_VECTOR
__interrupt void ADC12_ISR (void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(ADC12_VECTOR))) ADC12_ISR (void)
#else
#error Compiler not supported!
#endif
{
    if (ADC12MEM0 < 0x7FF)
      P1OUT &= ~0x01;                       // Clear P1.0 LED off
    else
      P1OUT |= 0x01;                        // Set P1.0 LED on
    __bic_SR_register_on_exit(CPUOFF);      // Clear CPUOFF bit from 0(SR)
}