MSP430F2274

这款单片机的ADC模块，选择ADC10的通道时候，手册里面有一个(VCC-VSS)/2，没看懂是什么意思，求帮忙解答 ，谢谢

Susan Yang：

这个就是指电源电压的一半，若是您选择了INCHx为1011，则表示这是电源电压的一半

若是选择了INCHx为1100，对于MSP430F2274则表示为A12

user6333565：

回复 Susan Yang:

什么是电源电压一半 说ADC的参考电压吗 还是啥 我想弄明白的是参考电压电一半指的是啥呢

Susan Yang：

回复 user6333565:

Up to eight external input channels (twelve on MSP430F22xx devices)

这里是指的输入通道，而A12等表示的是输入通道为固定值(VCC – VSS) / 2

看一下下面的例程，会对您有所帮助

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//******************************************************************************
//MSP430F22x4 Demo - ADC10, Sample A11, Lo_Batt, Set P1.0 if AVcc < 2.3V
//
//Description: A single sample is made on A11 (AVcc/2) with reference to
//internal 1.5V Vref. Software sets ADC10SC to start sample and conversion
//- ADC10SC automatically cleared at EOC. ADC10 internal oscillator times
//sample (16x) and conversion. ADC10BUSY flag is polled for EOC. If A11
//(AVcc/2) < 0311h (1.15V) indicating AVcc is less 2.3V, P1.0 set indicating
//a lo_Batt condition, else reset.
//
//MSP430F22x4
//-----------------
///|\|XIN|-
//| ||
//--|RSTXOUT|-
//||
//|A11 (AVcc/2) P1.0|-->LED
//
//A. Dannenberg
//Texas Instruments Inc.
//April 2006
//Built with CCE Version: 3.2.0 and IAR Embedded Workbench Version: 3.41A
//******************************************************************************
#include <msp430.h>int main(void)
{WDTCTL = WDTPW + WDTHOLD;// Stop WDTADC10CTL1 = INCH_11;// AVcc/2ADC10CTL0 = SREF_1 + ADC10SHT_2 + REFON + ADC10ON;TACCR0 = 30;// Delay to allow Ref to settleTACCTL0 |= CCIE;// Compare-mode interruptTACTL = TASSEL_2 + MC_1;// TACLK = SMCLK, Up mode__bis_SR_register(CPUOFF + GIE);// LPM0, TA0_ISR will force exitTACCTL0 &= ~CCIE;// Disable timer InterruptP1DIR |= 0x01;// Set P1.0 to output directionfor (;;){ADC10CTL0 |= ENC + ADC10SC;// Sampling and conversion startwhile (ADC10CTL1 & ADC10BUSY);// ADC10BUSY?if (ADC10MEM < 0x311)// ADC10MEM = A11 > 1.15V?P1OUT |= 0x01;// Set P1.0 LED onelseP1OUT &= ~0x01;// Clear P1.0 LED off}
}#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=TIMERA0_VECTOR
__interrupt void TA0_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(TIMERA0_VECTOR))) TA0_ISR (void)
#else
#error Compiler not supported!
#endif
{TACTL = 0;// Clear Timer_A control registersLPM0_EXIT;// Exit LPM0 on return
}