Hello,
I would like to measure the period of a square wave (around 1 kHz) with a timer in input capture configuration. I am using TIM5_CH3 on pin PA2 (nucleo G474RE).
I would like to receive a bit of help in debugging my code since i am not able to measure the period of an external waveform (also tracked on my oscilloscopes).
void TIM5_Init_ToMeasurePeriod (void){
// Enable the GPIOA Clock
RCC-> AHB2ENR |= (1<<0); // Enable the GPIOA clock writing 1 in bit 0
// Configure the GPIO
GPIOA -> MODER |= (1<<5); // Port PA2 configured as alternate function
GPIOA -> AFR[0] |= (1<<9); // Set alternate Function 2 i.e. TIM5_CH3 for PA2
// Enable the timer clock
RCC->APB1ENR1 |= (1<<3); // Enable the tim5 clock writing 1 in bit 3
// Set the timer timebase
TIM5 -> PSC = 1; // 80 MHz/2= 40MHz clock --> 0.025 us count set the resolution (1ms=40000 counts)
TIM5-> ARR = 0xFFFF;
TIM5 -> CCMR2 |= (1<<0); // CC3 channel configured as input and tim_ic3 is mapped on tim_ti3
TIM5 -> CCMR2 |= (1<<5); // Input capture filter set to N=4. 4 consecutive samples with the new level are required (to avoid noise during the toggling)
TIM5-> TISEL |= (0<<16); // TIM5_ch3 is the input of the timer
TIM5->CCER |= (1<<8)|(0<<0)|(0<<0); // Enable capture from the counter into the capture register
//TIM5->DIER |= (1<<3); // interupt enable for channel 3 not used now
// start the timer
TIM5 -> CR1|= TIM_CR1_CEN;
/* Clear the Capture event flag for channel 1 */
//TIM5->SR = ~TIM_SR_CC3IF;
}
uint32_t Period;
int main(void)
{
TIM5_Init_ToMeasurePeriod();
while (!(TIM5->SR & TIM_SR_CC3IF)){}
/* An active edge was detected, so store the timestamp */
period = TIM5 -> CCR3; // store the CCR register in 0.025 us counts
Thanks a lot
