MSP430I2041: ADC的位数问题

您是可以使用24bit的，但是由于没有24bit的数据，所以您需要使用 32bit的long

请参考下面的代码

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//******************************************************************************
//  MSP430i20xx Demo - SD24, Continuous Conversion on a Single Channel
//
//  Description: This program uses the SD24 module to perform continuous
//  conversions on a single channel. A SD24 interrupt occurs when a conversion
//  has completed.
//
//  Test by applying voltages to the input channel and setting a breakpoint
//  at the indicated line. Run program until it reaches the breakpoint, then use
//  the debugger's watch window to view the conversion results.
//
//  Results (upper 16 bits only) are stored in the array "results"
//
//  ACLK = 32kHz, MCLK = SMCLK = Calibrated DCO = 16.384MHz, SD_CLK = 1.024MHz
//  * Ensure low_level_init.c is included when building/running this example *
//
//  Notes: For minimum Vcc required for SD24 module - see datasheet
//         100nF cap btw Vref and AVss is recommended when using 1.2V ref
//
//               MSP430i20xx
//             -----------------
//         /|\|                |
//          | |                |
//          --|RST             |
//            |                |
//   Vin1+ -->|A0.0+      VREF |---+
//   Vin1- -->|A0.0-           |   |
//            |                |  -+- 100nF
//            |                |  -+-
//            |                |   |
//            |           AVss |---+
//
//  T. Witt
//  Texas Instruments, Inc
//  September 2013
//  Built with Code Composer Studio v5.5
//******************************************************************************
#include "msp430.h"

/* Array to store SD24 conversion results */
volatile int j, index = 0;
volatile unsigned long sum = 0;
unsigned long results[100];                     // Final results from running average

/* Defines */
#define SW_OVER_SAMPLING_FACTOR                 16

/* Main Function */
void main(void) {
    WDTCTL = WDTPW | WDTHOLD;                   // Stop WDT

    SD24CTL = SD24REFS;                         // Internal ref
    SD24INCTL0 = SD24GAIN_1;                    // Set gain on Channel 0
    SD24CCTL0 |= SD24IE;                        // Enable interrupt, OSR = 256 (default)

    __delay_cycles(3200);                       // Delay ~200us for 1.2V ref to settle

    SD24CCTL0 |= SD24SC;                        // Set bit to start conversion
    __bis_SR_register(GIE);                     // Enable interrupts

    while(1) {                                  // Loop endlessly, SET BREAKPOINT or PAUSE HERE
    }
}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=SD24_VECTOR
__interrupt void SD24_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(SD24_VECTOR))) SD24_ISR (void)
#else
#error Compiler not supported!
#endif
{
    long temp = 0;
    switch (__even_in_range(SD24IV,SD24IV_SD24MEM3)) {
        case SD24IV_NONE: break;
        case SD24IV_SD24OVIFG: break;
        case SD24IV_SD24MEM0:

            // Capture ADC data
            SD24CCTL0 &= ~SD24LSBACC;           // Clear LSBACC bit
            temp = SD24MEM0;                    // Read upper 16 bits of SD24MEM0
            SD24CCTL0 |= SD24LSBACC;            // Set LSBACC bit
            temp = temp*256 + (SD24MEM0&0xff);  // Read lower 16 bits of SD24MEM0, combine with upper bits

            // Perform software oversampling
            sum+= temp;                         // Add result to running sum
            j++;
            if(j >= SW_OVER_SAMPLING_FACTOR) {  // Calculate and store average
                results[index++] = sum/SW_OVER_SAMPLING_FACTOR;
                sum = 0;
                j = 0;
            }

            if(index >=100) {
                index=0;
            }
            break;
        case SD24IV_SD24MEM1: break;
        case SD24IV_SD24MEM2: break;
        case SD24IV_SD24MEM3: break;
        default: break;
    }
}