Posted on September 03, 2015 at 19:21
I'm having a problem where when I try to access an array from within a timer interrupt callback, everything seems to fall apart. To keep it simple, I have:
Timer 2 is set up to interrupt every 10us. Timer 3 is set up to interrupt every 10ms (1000x longer than Timer 2). Those interrupts are verified by toggling I/Os. That works great.
I have a 3 element array (RealTimeADCValue[3]), that I have continuous ADC conversion set up on ADC 0-2 with DMA. I can see those values in STM Studio and output them to a display. That works great too.
I'm trying to tally up a running total of the ADC channel 0 values with each Timer 2 tick. Essentially, tally up ADC values with each 10us tick (1000 samples) until Timer 3 rolls over, then store that total.
The callback code is:
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
if (htim->Instance==TIM2) //this timer is 1000x longer than TIM3
{
ADCSamplesLast=ADCSamplesWorking; //store number of samples taken, then reset
ADCSamplesWorking=0;
ADCTallyLast=ADCTallyWorking; //store the tally of ADC values, then reset
ADCTallyWorking=0;
}
if (htim->Instance==TIM3)
{
//ADCTallyWorking = ADCTallyWorking + RealTimeADCValue[0]; //add up the ADC values (have tried ''+='' as well...)
ADCSamplesWorking++; //inc count of samples taken
}
}
With it as-is, with the tallying of the ADC array commented out, it reads as expected, and ''ADCSamplesLast'' is ~1000. However, when I un-comment that line, the number of samples taken goes to like 2500, and it only stores one ADC value in ADCTallyLast. I even just tried reading ''RealTimeADCValue[0]'' into a dummy variable with the same results. Is there something I'm not getting about accessing an array, controlled by DMA, from within a callback?
Thanks for your input.
Joe
