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
1 ACCEPTED SOLUTION
Accepted Solutions
HI @KnarfB
My goal is to use the register based approach to mesure the period of an incoming square wave.
and basically I followed this paragraph in AN4776
this is my code now
void TIM3_Init_ToMeasurePeriod (void){
// configure PA6 pin to TIM3_CH1 with alternate function AF to measureperiod
// Enable the GPIOA Clock
RCC-> AHB2ENR |= (1<<0); // Enable the GPIOA clock writing 1 in bit 0
// Configure the GPIO
GPIOA -> MODER |= (1<<13); // Port PA6 configured as alternate function
GPIOA -> AFR[0] |= (1<<25); // Set alternate Function 2 i.e. TIM3_CH1 for PA6
// Enable the timer clock
RCC->APB1ENR1 |= (1<<1); // Enable the tim3 clock writing 1 in bit 1
// Set the timer timebase
TIM3 -> PSC = 1;
TIM3-> ARR = 0xFFFF; // it should set the lowest measurable framerate
TIM3 -> CCMR1 |= (1<<0); // CC1 channel configured as input
//TIM3 -> CCMR1 |= (1<<5); // Input capture filter set to N=4. 4 consecutive samples with the new level are required (to avoid noise during the toggling)
TIM3-> TISEL |= (0<<16);
// enable the capture compare
TIM3->CCER |= (1<<0); // Enable capture from the counter into the capture register
//TIM3->DIER |= (1<<3); // interrupt enable for channel 3
// start the timer
TIM3 -> CR1|= TIM_CR1_CEN;
}
uint32_t Timestamp;
int main(void)
{
TIM3_Init_ToMeasurePeriod();
/* Clear the Capture event flag for channel 3 */
//TIM3->SR = ~TIM_SR_CC1IF;
while (1)
{
TIM3->SR = ~TIM_SR_CC1IF;
while (!(TIM3->SR & TIM_SR_CC1IF));
/* An active edge was detected, so store the timestamp */
Timestamp = TIM3 -> CCR1; // store the CCR register in 0.025 us counts
}
}Can you help me in solving this?
Thanks
HI @Community member
These are the registers settings while I am doing input capture on PA6/Tim3_Ch1 with the code I shared in my last post
Ok I will try also to generate a pwm with this timer. I will let you know as soon as I do it
Thanks a lot
