STM32 PWM to stop after n pluses

[Wleon.1]

Is there a way to stop STM32 PWM after 10 pluses ?

I know one solution is using the system time and issue a stop via the code, however my issue is the stm CPU might be very busy to handle the stop signal.

[waclawek.jan]

Which STM32?

Use a timer which has the repetition counter (TIM_RTR), see TIM1/TIM8.

If there's no timer with TIM_RTR available, you can use another timer as master, in master-slave configuration, this timer in gated mode. Another option is to use DMA to load 0 into ARR or into CR1. Both these options are more complex than using the repetition counter.

JW

[Wleon.1]

Thanks for your reply, but how do you load 0 into ARR using DMA ? Is there any example ?

[waclawek.jan]

In the same way as you'd write to any other TIM register using DMA. Read the TIM, DMA chapters in the Reference Manual, and the Timer Cookbook application note AN4776.

JW

[Tesla DeLorean]

Which STM32?

What frequency, and how busy?

The STM32 could get an update interrupt at each pulse. Or at multiples with the repetition count. At 8-bit provides for 1 thru 256 as I recall.

Posted examples to forum before doing N pulse PWM using One-Shot Mode + Repetition Count

[Wleon.1]

Thanks for the reply, I tried the TIM DMA, and got the DMA and TIM register to the following settings, however it seems that no interrupt is happening, I don't see the ARR change. Can you help me check if my settings are correct ?

[waclawek.jan]

Okay, from the screenshots we can guess it's 'F723. You should've told us.

DMA1 Stream 0 (set to Channel 2) is triggered by TIM4_CH1, you should've set TIM4_DIER.CC1DE for that.

Then that should work, but IMO it's better to leave the trigger from update (DIER.UDE=1 as it is now), and use the respective DMA1 Stream 6 (at channel 2).

JW

[Wleon.1]

Hi thanks for the reply ! I have got the interrupt now and the DMA is running, however I encounter something very strange.

so I have set an data array

#define n 9
#define transfer 6
uint32_t buffer[n] = {500, 251, 252, 253, 504, 255, 506, 257, 258}; 
uint32_t DCR = 0x20B;

and I call the following function to kick start:

HAL_StatusTypeDef HAL_TIM_PWM_Start_DMA_MODIFIED(TIM_HandleTypeDef *htim, uint32_t Channel, uint32_t *pData, uint16_t Length)
{
  uint32_t tmpsmcr;
 
  /* Check the parameters */
  assert_param(IS_TIM_CCX_INSTANCE(htim->Instance, Channel));
 
  if (htim->State == HAL_TIM_STATE_BUSY)
  {
    return HAL_BUSY;
  }
  else if (htim->State == HAL_TIM_STATE_READY)
  {
    if ((pData == NULL) && (Length > 0U))
    {
      return HAL_ERROR;
    }
    else
    {
      htim->State = HAL_TIM_STATE_BUSY;
    }
  }
  else
  {
    /* nothing to do */
  }
 
  switch (Channel)
  {
    case TIM_CHANNEL_1:
    {
      /* Set the DMA compare callbacks */
      htim->hdma[TIM_DMA_ID_CC1]->XferCpltCallback = TIM_DMADelayPulseCplt;
      htim->hdma[TIM_DMA_ID_CC1]->XferHalfCpltCallback = TIM_DMADelayPulseHalfCplt;
 
      /* Set the DMA error callback */
      htim->hdma[TIM_DMA_ID_CC1]->XferErrorCallback = TIM_DMAError ;
 
      /* Enable the DMA stream */
      if (HAL_DMA_Start_IT(htim->hdma[TIM_DMA_ID_CC1], (uint32_t)pData, (uint32_t)&htim->Instance->DMAR, Length) != HAL_OK)  <----- i Change this from CCR1 to DMAR
      {
        return HAL_ERROR;
      }
 
      /* Enable the TIM Capture/Compare 1 DMA request */
      __HAL_TIM_ENABLE_DMA(htim, TIM_DMA_CC1);
      break;
    }
 
    default:
      break;
  }
 
int main(void)
{
...
 
 htim4.Instance->ARR = 1000;
  htim4.Instance->CCR1 = 100;
  HAL_TIM_PWM_Start_DMA_MODIFIED(&htim4, TIM_CHANNEL_1, buffer, transfer);
...
}
 

I wired a interrupt pin to the TIM output, and each interrupt i will save ARR and CCR1 to an array:

int arr[100] = {0};
int ccr1[100] = {0};
 
...
 
/**
  * @brief This function handles EXTI line[9:5] interrupts.
  */
void EXTI9_5_IRQHandler(void)
{
  /* USER CODE BEGIN EXTI9_5_IRQn 0 */
 
    if(i<100)
   {
      arr[i] =  htim4.Instance->ARR;
      ccr1[i] = htim4.Instance->CCR1;
   }else{
     //i++;
   }
   i++;
 
  /* USER CODE END EXTI9_5_IRQn 0 */
  HAL_GPIO_EXTI_IRQHandler(GPIO_PIN_5);
  /* USER CODE BEGIN EXTI9_5_IRQn 1 */
  
  /* USER CODE END EXTI9_5_IRQn 1 */
}

I was expecting:

arr[] = 1000, 500, 253 ...

ccr1[]=100, 251, 253 ...

what I actually got is:

arr[] = 1000, 1000, 252 ...

ccr1[]=100, 251, 504 ...

why is this so strange ? It says in the document if I set DCR to 0x20B, it should DMA 3 element in the array each time the DMA is triggered, why the pattern seems so "random".

here is my register set:

[waclawek.jan]

I don't understand what are you trying to do, but don't use both the CC1DE and UDE - use only UDE and change the DMA stream as I wrote above.

JW

[Wleon.1]

I am trying to change ARR and CCR1 for each and every pulses.