GPTIM_Input_Capture_Freq_Period_Measurement.c

#include "stm32f4xx.h"
int period;
float freq;

int main(){
	int last_value = 0;
	int current_value = 0;

	//Configure PA5 as alternate function mode
	RCC->AHB1ENR |= 0x1;					//Enable GPIOA
	GPIOA->MODER |= (2<<10);				//Set PA5 to alternate function mode
	GPIOA->AFR[0] |= (1<<20);				//Set PA5 to TIM2 Ch1
	
	//TIM2 Ch1 PA5 output compare @1Hz
	RCC->APB1ENR |= 0x1;					//Enable TIM2 Clock Bus
	TIM2->PSC = 1600-1;					//16.000.000 dive by 1.600 = 10.000 (Prescaler Register)
	TIM2->ARR = 10000-1;					//10.000 dive by 10.000 = 1Hz (Auto Reload Register)
	TIM2->CCMR1 |= 0x30;					//Set output to toggle on match (Capture/Compare Mode Register)
	TIM2->CCER |= 1;					//Enable CH1 compare mode (Capture/Compare Enable Register)
	TIM2->CCR1 = 0;						//Set match mode (Capture/Compare Register 1)
	TIM2->CNT = 0;						//Clear counter	(Counter)
	TIM2->CR1 |=1;						//Enable TIM2 counter (Control Registe 1)
	
	//Configure PA6 as alternate function mode
	RCC->AHB1ENR |=0x1;					//Enable GPIOA
	GPIOA->MODER |= (2<<12);				//Set PA6 to alternate function mode
	GPIOA->AFR[0]|= (2<<24);				//Set PA6 to TIM3 Ch1
	
	//TIM3 Ch1 PA6 input capture 
	RCC->APB1ENR |= 0x2;					//Enable TIM3 Clock Bus
	TIM3->PSC = 16000-1;					//1kHz
	TIM3->CCMR1 = 0x41;					//Set input capture 
	TIM3->CCER = 0xB;					//Capture Enable, Falling edge, Capture polarity
	TIM3->CR1 = 1;						//Enable TIM3 counter (Control Registe 1)
	

	while(1){
		while(!(TIM3->SR & 2));				//Wait until edge is captured
		current_value = TIM3->CCR1;
		period = current_value - last_value;
		last_value = current_value;
		freq = 1000/period;
	}
}