TIM3 periodElapsedCallback never called

[JustSomeGuy]

In my code, after setting an on-board LED, the timer is started like this.

 __HAL_TIM_SET_COUNTER(&htim3, 0);
while(HAL_TIM_Base_Start_IT(&htim3) != HAL_BUSY);

In debugging mode, I saw that the CNT register was in fact incrementing, however in would always rollover and would never trigger this callback function:

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
	if(htim->Instance == TIM3)
	{
		while(HAL_TIM_Base_Stop_IT(htim) != HAL_BUSY);
		HAL_GPIO_WritePin(GREEN_LED_GPIO_Port, GREEN_LED_Pin, RESET);
	}
}

 I saw on another forum post that someone suggested to put that code in stm32l0xx.c in the function TIM3_IRQHandler(). However when I did that, I found that the function was called instantly after HAL_TIM_Base_Start_IT(&htim3). 

What is going on here? I opened a new project with the EXACT same settings for timer 3, and it worked perfectly. This project has become far too massive to move everything over to a new project without a lot of headache. I would prefer to find out how to solve this in the project I am currently working on. Here is the cubeMX configuration:

static void MX_TIM3_Init(void)
{
  TIM_ClockConfigTypeDef sClockSourceConfig = {0};
  TIM_MasterConfigTypeDef sMasterConfig = {0};

  htim3.Instance = TIM3;
  htim3.Init.Prescaler = 2047;
  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim3.Init.Period = 7811;
  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  if (HAL_TIM_Base_Init(&htim3) != HAL_OK)
  {
    Error_Handler();
  }
  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK)
  {
    Error_Handler();
  }
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }
}

[Bob S]

Do you have the TIM3 interrupt enabled in the NVIC?  In CubeMX open the timer config window and click on the "NVIC Settings" tab.

[JustSomeGuy]

Yes, those have been enabled since the start.

[JustSomeGuy]

Here is some more information: I looked at the vector tables for both the original non-functioning program and the new functioning one. I found that TIM3_IRQHandler is mentioned in the non-functional project, but not the functional project.

[Karl Yamashita]

attach your IOC file.

[Karl Yamashita]

One thing i've noticed is that you're checking for HAL_BUSY when you call HAL_TIM_Base_Start_IT but the function only returns HAL_OK or HAL_ERROR. Not sure how you're getting past this or are you? You should be stuck here forever. 

while(HAL_TIM_Base_Start_IT(&htim3) != HAL_BUSY);

You also check for HAL_BUSY in the callback. This will be a stuck forever loop as well

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
	if(htim->Instance == TIM3)
	{
		while(HAL_TIM_Base_Stop_IT(htim) != HAL_BUSY);
		HAL_GPIO_WritePin(GREEN_LED_GPIO_Port, GREEN_LED_Pin, RESET);
	}
}

Change HAL_BUSY to HAL_OK which should fix your issue.

[JustSomeGuy]

I tried that method, and the interrupt worked once, but after that my B-L072Z-LRWAN1 board wouldn't receive LoRa data (this LED is an indicator for when data is received through LoRa). I switched the method to polling the CNT register and that worked with no issues. However, polling is not ideal. I would really like to know why this timer is malfunctioning like this in interrupt mode.

Another thing to consider, if the HAL_TIM_BASE_Start_IT() only returns HAL_ERROR or HAL_OK, it should always exit the while loop after 1 pass, since I am checking to make sure that the function does not return a value that it will never return. I still changed it to != HAL_OK though, just so it actually does something.

[JustSomeGuy · Accepted solution]

Some more information: I removed the function HAL_TIM_BASE_Stop_IT(), moved HAL_TIM_BASE_Start_IT() to the top of main(), and set a boolean value to indicate that the LED is set when I cleared the CNT register. in the interrupt callback, I check the timer instance and that boolean value to check whether the LED has been set. Now it's working flawlessly.

[Karl Yamashita]

---

Another thing to consider, if the HAL_TIM_BASE_Start_IT() only returns HAL_ERROR or HAL_OK, it should always exit the while loop after 1 pass, since I am checking to make sure that the function does not return a value that it will never return. I still changed it to != HAL_OK though, just so it actually does something.

---

If you don't receive HAL_BUSY, then there is no way to exit the while loop.

Instead you've should have tested for the return status to be not HAL_OK

	if(HAL_TIM_Base_Start_IT(&htim1) != HAL_OK)
	{
		// handle error
	}