input capture problem in coding

[svraj]

Hi friends, i am capturing frequency using timer pins(Input capture mode).

MCU = stm32f103c8t6

Software = Keil uvision 5

Debugger = st-link v2

• I capture frq using timer 1 ( TIM1_CC_IRQn ) channel 1 which is A8, which works awesome.
• I tried similarly with timer 2 ( TIM2_IRQn ) channel 1 which is A0, which is also capture frequency well. But sticks into the TIM2_IRQHandler. My program execution is like, first it completes the main function, then it goes to TIM2_IRQHandler function, then its not returning back to while loop. It sticks inside the TIM2_IRQHandler function, whether it i apply frequency to the pin or not.

I am getting this issue only when i use other timers except timer 1.

code is given below (Register level language)...

#include "stm32f10x.h"
 
int main()
{
RCC->APB1ENR |=RCC_APB1ENR_TIM2EN;
 
	TIM2->PSC=7199;
	TIM2->CCMR1 |=TIM_CCMR1_CC1S_0; // set T2[1] as input capture
	TIM2->CCER &=~TIM_CCER_CC1P; // Rising edge
	TIM2->CCMR1 &=~TIM_CCMR1_IC1PSC; // Diabling the PSC
	TIM2->DIER |=TIM_DIER_UIE|TIM_DIER_CC1IE;
	TIM2->CCER |=TIM_CCER_CC1E;
	TIM2->CR1 |= TIM_CR1_CEN;
	NVIC_EnableIRQ(TIM2_IRQn);
 
while(1)
{
// Not entering to while loop??
}
}
 
 
// Interrupt handler
void TIM2_IRQHandler(void)
{ 
 
	if ((TIM2->SR & TIM_SR_CC1IF) != 0)
{
 if ((TIM2->SR & TIM_SR_CC1OF) != 0) /* Check the overflow */
 {
 /* Overflow error management */
 gap = 0; /* Reinitialize the laps computing */
 TIM2->SR &= ~(TIM_SR_CC1OF | TIM_SR_CC1IF); /* Clear the flags */
 } 
 if (gap == 0) /* Test if it is the first rising edge */
 {
	
 counter0 = TIM2->CCR1; /* Read the capture counter which clears the
 CC1ICF */
		
	 
 gap = 1; /* Indicate that the first rising edge has yet been detected */
 }
 else
 {
 counter1 = TIM2->CCR1; /* Read the capture counter which clears the
 CC1ICF */
	 
 if (counter1 > counter0) /* Check capture counter overflow */
 {
 Counter = counter1 - counter0;
	Frequency=10000/Counter; 
	 RPM=(Frequency*60)/4;
 }
 else
 {
 Counter = counter1 + 0xFFFF - counter0 + 1;
	 	Frequency=10000/Counter; 
			 RPM=(Frequency*60)/4;
 
 }
 counter0 = counter1; 
 }
}
else
{
 /* Unexpected Interrupt */	
 /* Manage an error for robust application */
} 
 
}

I think there is a mistake in my code in interrupt handler, kindly guide me friends to solve the issue.

[waclawek.jan]

You enable Update Interrupt

TIM2->DIER |=TIM_DIER_UIE|TIM_DIER_CC1IE;

but you then don't manage it (clear its flag) in the ISR.

JW

[svraj]

Thank you waclawek, rightly spot

After clearing the flag it works fine.