MSP430F149使用P6口采集外部电压时受IO口电压影响，怎么解决？？

P6口上电后就有2.7V左右电压。将外部待采集电压接入后外部电压受到IO口输出电压的影响改变实际电压。特别是当采集小电压（零点几伏）时，电压被拉高到1.6V左右。请问这问题该如何解决？？感谢解答！！

灰小子：

你好，你的io是怎么配置的？电路又是怎么样的？

jianfeng Chou：

回复 灰小子:

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。

灰小子：

回复 jianfeng Chou:

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|-
//| ||
//--|RSTXOUT|-
//||
//Vin-->|P6.0/A0P1.0|--> 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 WDTADC12CTL0 = SHT0_2 + ADC12ON;// Set sampling time, turn on ADC12ADC12CTL1 = SHP;// Use sampling timerADC12IE = 0x01;// Enable interruptADC12CTL0 |= ENC;// Conversion enabledP6SEL |= 0x01;// P6.0 ADC option selectP1DIR |= 0x01;// P1.0 outputfor (;;){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 offelseP1OUT |= 0x01;// Set P1.0 LED on__bic_SR_register_on_exit(CPUOFF);// Clear CPUOFF bit from 0(SR)
}