NUCLEO F411RE timer in order to generate an interrupt

[Roman_E]

Learning on how to code 4x4 keypad with F411RE I came to need to learn 

timer in order to generate an interrupt (saying simply C function should be called lets say every 1 second) 
I created STM32 project CubeIDE+CubeMX  selected TIM3 (in Timers)  -> set Clock Source to InternalClock, set Prescaler ( PSC... ) to 8399 ( googled, found example ),
set Counter Period to 9999 and set NVIC checkmark for TIM3 (enabled)
 Saved IOC file and CubeMX generated some code for me.
In stm32f4xx_it.c file I added 

void TIM3_IRQHandler(void)
{
 /* USER CODE BEGIN TIM3_IRQn 0 */

 /* USER CODE END TIM3_IRQn 0 */
 HAL_TIM_IRQHandler(&htim3);
 /* USER CODE BEGIN TIM3_IRQn 1 */
 HAL_GPIO_TogglePin(LD2_GPIO_Port, LD2_Pin);
 /* USER CODE END TIM3_IRQn 1 */
}

and running the code I expected to see blinking LED ( at least wanted no matter 1 sec or 0.5 sec )

but nothing happens
Did I miss something ? ( I'm learning this stuff )

 

[TDK]

Did you start the timer with interrupts enabled? Is global TIM3 interrupt enabled in IOC?

Should be a HAL_TIM_Base_Start_IT or similar statement in your user code to start the timer.

[Roman_E]

Is TIM3 interrupt enabled in IOC?   Yes , I checkmarked in NVIC CubeMX
I found HAL_TIM_Base_Start_IT  in Drivers/STM32F4xx_HAL_Driver folder header and c source files with HAL_TIM_Base_Start_IT  function
Should I add where ? to main.c file? Logically Yes , I should add "staring TIM3"

before while loop

 

[mfgkw]

(Edit: comment out HAL_TIM_Base_Start())

Probably you missed in main.c:

static void MX_TIM3_Init(void)
{
...
 /* USER CODE BEGIN TIM3_Init 2 */
 HAL_TIM_Base_Start_IT(&htim3);
 // HAL_TIM_Base_Start(&htim3);
 /* USER CODE END TIM3_Init 2 */

}

 

[mfgkw]

Great to hear it works.

 

Besides your initial problem a suggestion:

You modified void TIM3_IRQHandler(void) in stm32f4xx_it.c to toggle your LED pin.

The (unmodified) function calls HAL_TIM_IRQHandler(&htim3) from stm32f4xx_hal_tim.c, which in turn calls HAL_TIM_PeriodElapsedCallback(htim).

The latter is a weak function defined empty in stm32f4xx_hal_tim.c:

/**
 * @brief Period elapsed callback in non-blocking mode
 * @PAram htim TIM handle
 * @retval None
 */
__weak void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
 /* Prevent unused argument(s) compilation warning */
 UNUSED(htim);

 /* NOTE : This function should not be modified, when the callback is needed,
 the HAL_TIM_PeriodElapsedCallback could be implemented in the user file
 */
}

HAL_TIM_PeriodElapsedCallback is declared weak as it is intended to be defined somewhere else with more functionality.

 

Long story short: You may override the weak callback function in your code, e.g. in main.c without fiddling with stm32f... files.

main.c might then look like this:

...
/* USER CODE BEGIN 4 */

void HAL_TIM_PeriodElapsedCallback( TIM_HandleTypeDef *htim )
{
 if( htim == &htim3 )
 {
 HAL_GPIO_TogglePin( LED_GPIO_Port, LED_Pin );
 }
}

/* USER CODE END 4 */
...

 This keeps your code together and apart from ST defined code.

[Roman_E]

Thank you for your advice !
As I'm learning on how to use 4x4 keypad with F411re, I understand , that this interrupt function should be called periodically. Frequency it should be called based on Prescaler&Period ( at simple case + can be configured via CubeMX) 

htim3.Init.Prescaler = 8399;
htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
htim3.Init.Period = 4499;

What would be your suggestion on "frequency to call the interrupt function" ?
I understand that in this function I need to add code "to scan 4x4 rows and columns". But how often this function should be called ? Every 10 ms ? 20ms?

[Andrew Neil]

I think your questions here - generating a timer interrupt - has now been answered?

Is so, please mark the solution on the post which provided the answer.

 

You already have a separate thread on 4 x 4 keypad with Nucleo 411RE and HAL, and @gbm has already given a suggestion for the scan rate there...

[Gyessine]

Hello @Roman_E 
Hope you enjoy your time learning about timers
you can follow the steps of this article. It will help you learn how to do 1 second interruptions with timers
BR
Gyessine