MSP430I2041: ADC的位数问题

根据数据手册的描述 ADC为24位，但是提供的demo程序接收转换结果是16位的，而且查看ADC的数据寄存器也是16位的

Susan Yang：

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_FACTOR16/* Main Function */
void main(void) {WDTCTL = WDTPW | WDTHOLD;// Stop WDTSD24CTL = SD24REFS;// Internal refSD24INCTL0 = SD24GAIN_1;// Set gain on Channel 0SD24CCTL0 |= SD24IE;// Enable interrupt, OSR = 256 (default)__delay_cycles(3200);// Delay ~200us for 1.2V ref to settleSD24CCTL0 |= SD24SC;// Set bit to start conversion__bis_SR_register(GIE);// Enable interruptswhile(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 dataSD24CCTL0 &= ~SD24LSBACC;// Clear LSBACC bittemp = SD24MEM0;// Read upper 16 bits of SD24MEM0SD24CCTL0 |= SD24LSBACC;// Set LSBACC bittemp = temp*256 + (SD24MEM0&0xff);// Read lower 16 bits of SD24MEM0, combine with upper bits// Perform software oversamplingsum+= temp;// Add result to running sumj++;if(j >= SW_OVER_SAMPLING_FACTOR) {// Calculate and store averageresults[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;}
}

,

?? ?：

非常感谢

,

Susan Yang：

很高兴能帮到您！