ADC wont work without delay or setting GIE bit inside ISR

Aaron,

you mean this code?

//******************************************************************************
//   MSP430F552x Demo - ADC12, Sample A0, Set P1.0 if A0 > 0.5*AVcc
//
//   Description: A single sample is made on A0 with reference to AVcc.
//   Software sets ADC12SC to start sample and conversion - ADC12SC
//   automatically cleared at EOC. ADC12 internal oscillator times sample (16x)
//   and conversion. In Mainloop MSP430 waits in LPM0 to save power until ADC12
//   conversion complete, ADC12_ISR will force exit from LPM0 in Mainloop on
//   reti. If A0 > 0.5*AVcc, P1.0 set, else reset.
//
//                MSP430F552x
//             -----------------
//         /|\|                 |
//          | |                 |
//          --|RST              |
//            |                 |
//     Vin -->|P6.0/CB0/A0  P1.0|--> LED
//
//   Bhargavi Nisarga
//   Texas Instruments Inc.
//   April 2009
//   Built with CCSv4 and IAR Embedded Workbench Version: 4.21
//******************************************************************************

#include <msp430.h>

int main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  ADC12CTL0 = ADC12SHT02 + ADC12ON;         // Sampling time, ADC12 on
  ADC12CTL1 = ADC12SHP;                     // Use sampling timer
  ADC12IE = 0x01;                           // Enable interrupt
  ADC12CTL0 |= ADC12ENC;
  P6SEL |= 0x01;                            // P6.0 ADC option select
  P1DIR |= 0x01;                            // P1.0 output

  while (1)
  {
    ADC12CTL0 |= ADC12SC;                   // Start sampling/conversion
    
    __bis_SR_register(LPM0_bits + GIE);     // LPM0, ADC12_ISR will force exit
    __no_operation();                       // For debugger
  }
}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector = ADC12_VECTOR
__interrupt void ADC12_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(ADC12_VECTOR))) ADC12_ISR (void)
#else
#error Compiler not supported!
#endif
{
  switch(__even_in_range(ADC12IV,34))
  {
  case  0: break;                           // Vector  0:  No interrupt
  case  2: break;                           // Vector  2:  ADC overflow
  case  4: break;                           // Vector  4:  ADC timing overflow
  case  6:                                  // Vector  6:  ADC12IFG0
    if (ADC12MEM0 >= 0x7ff)                 // ADC12MEM = A0 > 0.5AVcc?
      P1OUT |= BIT0;                        // P1.0 = 1
    else
      P1OUT &= ~BIT0;                       // P1.0 = 0

    __bic_SR_register_on_exit(LPM0_bits);   // Exit active CPU
  case  8: break;                           // Vector  8:  ADC12IFG1
  case 10: break;                           // Vector 10:  ADC12IFG2
  case 12: break;                           // Vector 12:  ADC12IFG3
  case 14: break;                           // Vector 14:  ADC12IFG4
  case 16: break;                           // Vector 16:  ADC12IFG5
  case 18: break;                           // Vector 18:  ADC12IFG6
  case 20: break;                           // Vector 20:  ADC12IFG7
  case 22: break;                           // Vector 22:  ADC12IFG8
  case 24: break;                           // Vector 24:  ADC12IFG9
  case 26: break;                           // Vector 26:  ADC12IFG10
  case 28: break;                           // Vector 28:  ADC12IFG11
  case 30: break;                           // Vector 30:  ADC12IFG12
  case 32: break;                           // Vector 32:  ADC12IFG13
  case 34: break;                           // Vector 34:  ADC12IFG14
  default: break; 
  }
}

And it does not run in it's original version?

Dennis

The “__bic_SR_register_on_exit” instructs the compiler to clear these bits in the Status Register just before it will leave the ISR function and jumps back to main.

 

I think the ADC generates continuously interrupts and therefore you don’t see LED changes. Adding a delay or disable interrupts lengths the ADC ISR time and gives you the possibility to see LED changes.

 

What you need to do is clearing all ADC interrupt flags, either once in main or in the ADC ISR. You can also have a look which flags are set and why.

Access/read or write of the ADC12IV will (normally) reset the highest pending interrupt flag. What is the program doing when debugging it? Does it access the ISR? Only once or repeated? Does it jump back to main starting a new conversion?

Edit: Sorry, forget that question! You wrote that it works in debug mode.

(The code we're talking about uses driverlib.)

Actually, it is not ADC12IV but the access of the memory register that clears the corresponding interrupt flag.(Which implies that the behaviour could be explained by a conversion that happened in another memory register, which should not be possible.)

Aaron, does the problem remain if you do ADC12IFG=0; at the end of the interrupt function?

Clemens Ladisch said:

Aaron, does the problem remain if you do ADC12IFG=0; at the end of the interrupt function?

No that does not help, unfortunately. It still has the same behavior. Are interrupts being disabled somehow?

What i am confused by is why adding the delay makes it work without the +GIE inside the __bic_SR_on_exit function.

see my latest post, clearing the ADCIFG doesn't seem to help.

Dennis Eichmann , using that code that modifies registers (instead of using driver lib functions to do so) seems to work fine outside the debugger! So this must be an issue with the driverlib.