Why is my timer 4 interrupt issued as soon as I enable the interrupt?

[arnold_w]

Posted on February 01, 2016 at 10:26

I want to generate an interrupt after 2 seconds and I am running at 32 MHz. However, my interrupt is issued as soon as I enable the interrupt. What am I doing wrong?

void testTimer4(EventCallback_t timerInterruptCallback)
{
timerInterruptCallback_ = timerInterruptCallback;
RCC->APB1ENR |= RCC_APB1ENR_TIM4EN;
TIM4->PSC = 976;
TIM4->ARR = 65505;
TIM4->CNT = 0;
TIM4->SR &= (~TIM_SR_UIF);
TIM4->DIER |= TIM_DIER_UIE;
HAL_NVIC_EnableIRQ(TIM4_IRQn);
TIM4->CR1 |= TIM_CR1_CEN;
}
void TIM4_IRQHandler(void)
{
TIM4->SR &= (~TIM_SR_UIF);
HAL_NVIC_DisableIRQ(TIM4_IRQn);
TIM4->DIER &= (~TIM_DIER_UIE);
TIM4->CR1 &= (~TIM_CR1_CEN);
RCC->APB1ENR &= (~RCC_APB1ENR_TIM4EN);
(void)timerInterruptCallback_((uint32_t)TIMER_4_EXPIRED, 0);
}

[Radosław]

Posted on February 01, 2016 at 10:36

You change prescaler, in configuration stage generate software uptade then clear all flags.

Your code looks very strange.

TIM4->SR &= (~TIM_SR_UIF);
TIM4->DIER |= TIM_DIER_UIE;
 Don't use RMW editing on SR registers. You don,t check if coresponding interrupt is enabled. 
 sign ~ should be before ( etc. 
 Mixing HAL and reg style is *****. 

[Walid FTITI_O]

Posted on February 01, 2016 at 11:45

Hi arnold_w,

Check this discussion about the “Timer interrupt after start�?:

https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=https%3a//my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/F427%20-%20Timer%20interrupts%20right%20after%20start&FolderCTID=0x01200200770978C69A1141439FE559EB459D7580009C4E14902C3CDE46A77F0FFD06506F5B...

.

You be inspired there from my recommendations.

-Hannibal-

[arnold_w]

Posted on February 01, 2016 at 12:56

Thank you for your replies. So, the problem was that I forgot to update the prescalar after it was set. The following code works great.

void testTimer4(EventCallback_t timerInterruptCallback)

{ timerInterruptCallback_ = timerInterruptCallback; RCC->APB1ENR |= RCC_APB1ENR_TIM4EN; TIM4->PSC = 976; TIM4->EGR = TIM_EGR_UG; // Generate an update event to reload the Prescaler TIM4->ARR = 65505; TIM4->CNT = 0; TIM4->SR &= (~TIM_SR_UIF); TIM4->DIER |= TIM_DIER_UIE; HAL_NVIC_EnableIRQ(TIM4_IRQn); TIM4->CR1 |= TIM_CR1_CEN; } void TIM4_IRQHandler(void) { TIM4->SR &= (~TIM_SR_UIF); HAL_NVIC_DisableIRQ(TIM4_IRQn); TIM4->DIER &= (~TIM_DIER_UIE); TIM4->CR1 &= (~TIM_CR1_CEN); RCC->APB1ENR &= (~RCC_APB1ENR_TIM4EN); (void)timerInterruptCallback_((uint32_t)TIMER_4_EXPIRED, 0); }