SLAA475A October   2010  – March 2019 MSP430L092

 

  1.   MSP430x09x Analog Pool: Feature Set and Advanced Use
    1.     Trademarks
    2. 1 MSP430x09x Overview
    3. 2 Analog Pool (A-Pool)
      1. 2.1  Input Dividers
      2. 2.2  Internal Reference
      3. 2.3  Starting and Stopping the A-Pool
      4. 2.4  Comparator Function
      5. 2.5  8-Bit DAC Function
      6. 2.6  8-Bit ADC Function
        1. 2.6.1 ADC Conversion Using Ramp
          1. 2.6.1.1 ADC Conversion Without Error Compensation
          2. 2.6.1.2 ADC Conversions With Overdrive Compensation
          3. 2.6.1.3 ADC Conversions With Offset Compensation
          4. 2.6.1.4 ADC Conversions With Overall Compensation
          5. 2.6.1.5 Windowed ADC Conversion
        2. 2.6.2 ADC Conversion Using SAR
        3. 2.6.3 Multiple ADC Conversions
        4. 2.6.4 Comparison Between Different Measurement Methods
        5. 2.6.5 Error Dependencies
      7. 2.7  SVM Function
      8. 2.8  Use of Multiple Features
      9. 2.9  Temperature Measurements With the A-Pool
      10. 2.10 Fractional and Integer Number Use
      11. 2.11 APINTB and APFRACTB Use With ATBU and EOCBU
      12. 2.12 A-Pool Trigger Sources
      13. 2.13 Filtering ADC Conversions With Digital Filters
    4. 3 Summary
    5. 4 References
  2.   Revision History

2.6.2 ADC Conversion Using SAR

In addition to the ramp method, a SAR conversion is also implemented. Within 8 clock cycles, the SAR implementation reaches the measured value with an accuracy of 1 bit. The SAR logic does not compensate for any internal offsets of the A-Pool module. The following code shows the settings to use the SAR logic.

#include "msp430l092.h" unsigned char result; // Result variable void main( void ) { // Stop watchdog timer to prevent time out reset WDTCTL = WDTPW + WDTHOLD; APCNF = CMPON+DBON+CONVON+APREFON; // Enable comparator on + // Enable DAC buffer + // Enable conversion + // Enable reference APVDIV = A0DIV; // Set 500mV input range APIE |= EOCIE; // Enable end of conversion interrupt APOMR |= SAREN; // Enable SAR logic _BIS_SR(GIE); // Switch on global interrupts APCTL = APPSEL0+APPSEL2+OSEL+RUNSTOP; // Set DAC buffer output to PSEL + // Select output buffer + // Start conversion _BIS_SR(LPM0); // Go to LPM0 asm("nop"); while(1); } #pragma vector=APOOL_VECTOR // A-Pool interrupt service routine __interrupt void APOOL_ISR(void) { switch(__even_in_range(APIV,8)) // Add offset to PC and delete flag { case 0: break; case 2: result = APINT; // Save value in variable break; case 4: break; case 6: break; case 8: break; default: break; } }