CODEWITHSUNDEEP
timerinterruptstm32
michaelm700
michaelm700

Reputation: 19

Why doesn't this simple STM32F756 timer code work?

Sourced to internal clock at APB1=96 MHz, I want to start a count up from zero via software command and generate a timer interrupt when the auto-reload register value is reached. I can only get the interrupt to fire if I use the HAL function HAL_TIM_Base_Start_IT that both activates the UPDATE interrupt and starts the clock. But then it fires immediately instead of waiting for the count to be reached?

//********** timer initialization  ************************************
static void MX_TIM3_Init(void)
{

  TIM_ClockConfigTypeDef sClockSourceConfig;
  TIM_MasterConfigTypeDef sMasterConfig;

  htim3.Instance = TIM3;
  htim3.Init.Prescaler = 1000;
  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim3.Init.Period = 1000;
  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  if (HAL_TIM_Base_Init(&htim3) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != 
   HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }
}

//************  timer activation code in main program  ******************
    HAL_NVIC_DisableIRQ(TIM3_IRQn);
    TIM3->CR1 |= 0;
    TIM3->CNT=0;
    HAL_NVIC_ClearPendingIRQ(TIM3_IRQn);
    HAL_NVIC_EnableIRQ(TIM3_IRQn);
    TIM3->CR1 |= 1;

//****************   timer ISR  ***************************************
void TIM3_IRQHandler(void)
{
  doStuff();

  HAL_NVIC_ClearPendingIRQ(TIM3_IRQn);
  HAL_TIM_IRQHandler(&htim3);
}

Upvotes: 1

Views: 1679

Answers (1)

LoriB
LoriB

Reputation: 381

If you don't want the interrupt to fire immediately after the start, try clearing the UPDATE flag before starting the timer:

if (HAL_TIM_Base_Init(&htim3) != HAL_OK)
{
  _Error_Handler(__FILE__, __LINE__);
}

__HAL_TIM_CLEAR_FLAG(&htim3, TIM_IT_UPDATE);

if(HAL_TIM_Base_Start_IT(&htim3) != HAL_OK)
{
  _Error_Handler(__FILE__, __LINE__);
}

Upvotes: 3

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