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

arnold_w
Senior
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);
}

3 REPLIES 3
Radosław
Senior II
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
Senior II
arnold_w
Senior
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);

}