刚开始使用MSP430，想用msp430FR4133 检测电池电压

zengbo wang 说：

利用片内基准电压1.5V 反推电池电压，DVCC做参考电压怎么连接？

不需要外部连接。

//******************************************************************************
//  MSP430FR413x Demo - ADC, Lo_Batt, Set P1.0 if AVcc < 2.50V
//
//  Description: A single sample is made on A13 (Vref) with reference set to
//  DVCC. Software sets ADC10SC to start sample and conversion
//  - ADC10SC automatically cleared at EOC. Once conversion is completed, the
//  following equation is used to calculate DVCC = (1023 * 1.5) / adcResult.
//  if DVCC is < 2.5V, P1.0 set indicating a lo_Batt condition, else reset.
//
//                MSP430FR4133
//             -----------------
//         /|\|              XIN|-
//          | |                 |
//          --|RST          XOUT|-
//            |                 |
//            |A13 (Vref)   P1.0|-->LED
//
//  Ling Zhu
//  Texas Instruments Inc.
//  Mar 2017
//  Built with IAR Embedded Workbench v6.50 & Code Composer Studio v7.0.1
//******************************************************************************
#include <msp430.h>

unsigned int adcResult;                     // Temporarily stores the ADC value
                                            // that was read from ADCMEM0
int main(void)
{
    volatile unsigned long dvccValue;       // Calculated DVCC value

    WDTCTL = WDTPW | WDTHOLD;               // Stop WDT

    P1DIR |= BIT0;                          // Set P1.0 to output direction

    // Disable the GPIO power-on default high-impedance mode to activate
    // previously configured port settings
    PM5CTL0 &= ~LOCKLPM5;

    // Configure ADC10
    ADCCTL0 &= ~ADCENC;                     // Disable ADC
    ADCCTL0 = ADCSHT_2 | ADCON;             // ADCON, S&H=16 ADC clks
    ADCCTL1 = ADCSHP;                       // ADCCLK = MODOSC; sampling timer
    ADCCTL2 = ADCRES;                       // 10-bit conversion results
    ADCIE = ADCIE0;                         // Enable ADC conv complete interrupt
    ADCMCTL0 = ADCINCH_13 | ADCSREF_0;      // A13 ADC input select = 1.5V Ref
                                            // Vref = DVCC
    // Configure reference module located in the PMM
    PMMCTL0_H = PMMPW_H;                    // Unlock the PMM registers
    PMMCTL2 |= INTREFEN;                    // Enable internal reference
    while(!(PMMCTL2 & REFGENRDY));          // Poll till internal reference settles

    while(1)
    {
        ADCCTL0 |= ADCENC | ADCSC;          // Sampling and conversion start
        __bis_SR_register(LPM0_bits | GIE); // Enter LPM0, ADC_ISR will force exit
        __no_operation();                   // For debug only

        // To calculate DVCC, the following equation is used
        // DVCC = (1023 * 1.5) / adcResult
        // The following equation is modified to use only integers instead
        // of using float. All results needs to be divided by 100 to obtain
        // the final value.
        // DVCC = (1023 * 150) / adcResult
        dvccValue = ((unsigned long)1023 * (unsigned long)150) / (unsigned long) (adcResult);

        if (dvccValue < 250)                // DVCC < 2.50V ?
            P1OUT |= BIT0;                  // Set P1.0 LED on
        else
            P1OUT &= ~BIT0;                 // Clear P1.0 LED off
    }
}

// ADC interrupt service routine
#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=ADC_VECTOR
__interrupt void ADC_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(ADC_VECTOR))) ADC_ISR (void)
#else
#error Compiler not supported!
#endif
{
    switch(__even_in_range(ADCIV, ADCIV_ADCIFG))
    {
        case ADCIV_NONE:
            break;
        case ADCIV_ADCOVIFG:
            break;
        case ADCIV_ADCTOVIFG:
            break;
        case ADCIV_ADCHIIFG:
            break;
        case ADCIV_ADCLOIFG:
            break;
        case ADCIV_ADCINIFG:
            break;
        case ADCIV_ADCIFG:
            adcResult = ADCMEM0;            // Read ADC memory
            __bic_SR_register_on_exit(LPM0_bits);// Exit from LPM
            break;
        default:
            break;
    }
}