Basic timer that doesn't work STM32L4

Question

I'm trying to use timer2 in STM32L475 but it doesn't start firing the interrupt at all.

I would like to configure the timer for a minute.

void InitializeTimer()
{
 TIM_SlaveConfigTypeDef sSlaveConfig;
 TIM_MasterConfigTypeDef sMasterConfig;
 htim2.Instance = TIM2;
 htim2.Init.Prescaler = 10000;
 htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
 htim2.Init.Period = 500;
 htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
 if (HAL_TIM_Base_Init(&htim2) != HAL_OK)
 {
 _Error_Handler(__FILE__, __LINE__);
 }
 sSlaveConfig.SlaveMode = TIM_SLAVEMODE_RESET;
 sSlaveConfig.InputTrigger = TIM_TS_ITR0;
 if (HAL_TIM_SlaveConfigSynchronization(&htim2, &sSlaveConfig) != HAL_OK)
 {
 _Error_Handler(__FILE__, __LINE__);
 }
 sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
 sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
 if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK)
 {
 _Error_Handler(__FILE__, __LINE__);
 }
if(HAL_TIM_Base_Start_IT(&htim2) != HAL_OK)
{
 _Error_Handler(__FILE__, __LINE__);
}
}
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
 if (htim->Instance == TIM2) {
 start_processing = true;
 }
}
void TIM2_IRQHandler()
{
 /* Clear interrupt flag first. It cannot be the last instruction in an interrupt handler. */
 __HAL_TIM_CLEAR_FLAG(&htim2, TIM_FLAG_UPDATE); //clear interrupt flag
 start_processing = true;
}

before main loop:

 MX_I2C3_Init();
 InitializeTimer();
 //MX_SPI3_Init();
 HAL_NVIC_SetPriority(TIM2_IRQn, 0, 1);
 HAL_NVIC_EnableIRQ(TIM2_IRQn);// Enable interrupt from TIM3 (NVIC level)

• followed Monica to Codidact: Some things to check: Does it start counting and reach the limit? What is the master timer (TIM1?) doing? Does it work without the master-slave configuration? Is start_processing declared as volatile? What do the control and status registers contain?
• Andre: @berendi yes start_processing declared as volatile. Can you show a basic setup without master and slave ?
• Andre: @berendi HAL_TIM_PeriodElapsedCallback is never called
• followed Monica to Codidact: The period value seems to be way too low for one minute. Does the controller run in some reduced frequency (low power) mode?

Answer 1

HAL_TIM_PeriodElapsedCallback() is never called because there is no code to call it. It is supposed to be called from TIM2_IRQHandler().

Here is a basic timer setup with interrupts every minute, assuming the APB1 clock is 80 MHz.

volatile int start_processing;
void TIM2_IRQHandler(void) {
 if(TIM2->SR & TIM_SR_UIF) { // check status
 start_processing = 1;
 TIM2->SR &= ~TIM_SR_UIF; // clear status
 }
}
void InitializeTimer(void) {
 RCC->APB1ENR1 |= RCC_APB1ENR1_TIM2EN;
 RCC->APB1ENR1;
 TIM2->PSC = 9999; // 80 MHz clock is prescaled to 8 kHz
 TIM2->EGR = TIM_EGR_UG; // required to take over the ARR value
 TIM2->ARR = 479999; // 8000 * 60 - 1
 TIM2->DIER = TIM_DIER_UIE; // enable update (timer overflow) interrupt
 TIM2->CR1 = TIM_CR1_CEN; // start timer
 NVIC_SetPriority(TIM2_IRQn, 0);
 NVIC_EnableIRQ(TIM2_IRQn);
}