CODEWITHSUNDEEP
microcontrollermsp430adc
StanislavOssovsky
StanislavOssovsky

Reputation: 37

12-bit ADC in MSP430FR2476 seems to only work in 10-bit mode

Here is the problem: I am trying to initialize the 12-bit built-in ADC on MSP430FR2476, but no matter what I do it seems to work at 10 bits. I change the resolution bits in a control register and alas, to no avail. No matter what I have tried nothing helps, always 10 bits. The most significant byte never gets higher than 3. Please help, here is a snippet of the code:

 //Configuring ADC

  PMMCTL2 |= (INTREFEN);            //Internal reference, default 1.5V
  ADCCTL0=ADCCTL1 = 0;              //Ensuring that the ADC is off
  ADCCTL0 |= (ADCSHT_7 + ADCMSC);   //sample and hold = 64clk, multiple conversion
  ADCCTL1 |= (ADCSHP + ADCSSEL_2 + ADCCONSEQ_1 + ADCDIV_7);        //Conversion is triggered 
                                   //manually, ADC clock source - SMCLK/8 ~ 2Mhz, sequence of 
                                             //channels single conversion,
  ADCCTL2 |= (ADCRES_2);         //12 bit resolution, no matter what setting I have, no change
  ADCMCTL0 |= (ADCSREF_1 + ADCINCH_1);       //Employing the internal reference and starting 
                                             //conversion from A1 (P1.1)
  ADCIE |= ADCIE0;                           //Activate interrupt
  ADCCTL0 |= (ADCON);                        //Switching ADC on
  SYSCFG2 |= (BIT1);                         //Activate ADC module on the pins (this line 
                                             //doesn't do anything for some reason

void adc_convert_begin(){
    ADCCTL0 |= ADCENC;
    ADCCTL0 |= ADCSC;           //Start conversion
      

//The interrupt simpy send the most significant byte over UART
__attribute__((interrupt(ADC_VECTOR)))
void ADC_ISR(void){
    switch(__even_in_range (ADCIV, 0x0C)){
    case 0x0C:
        adc_data[adc_index] = ADCMEM0;
        UCA1TXBUF = (unsigned char)(ADCMEM0>>8);
        break;
    }
}

Upvotes: 1

Views: 337

Answers (1)

StanislavOssovsky
StanislavOssovsky

Reputation: 37

The error happens to be here:

ADCCTL2 |= (ADCRES_2);

The idea is the default value is 1, so when I perform an |= operation on the register, the final value turns out to be 3, instead of 2. I need to zero that bit field first!

Upvotes: 0

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