Input capture problem

Hi everyone!

I'm trying to measure a PWM frequency signal using the input capture channel 1 of TIM3, but it won't work.

i'm using NUCLEO F446RE board, here is my code:

#include "stm32f4xx.h" // Device header
#include "lcd_H.h"

int main(void)
{
uint16_t capt1 = 0, capt2 = 0;
uint8_t lock = 1;
float Freq = 0.00;
//Clock Setup

RCC ->CR |= 1 << 18; //Enable bypass HSE
RCC ->CR |= 1 << 16; //Enable HSE
while(!(RCC ->CR & (1 << 17))); //wait HSE is ready
RCC ->CFGR &= ~(1 << 1); //HSE is used as system clock
RCC ->CFGR |= 1 << 0;

/**************************************************************************************/
//Configure PA6 as Input Capture channel 1

RCC ->AHB1ENR |= 1 << 0; //Enable clock for GPIOA

GPIOA ->MODER &= ~(1 << 12); //PA6 is used as Alternate function Mode: 10
GPIOA ->MODER |= (1 << 13);
GPIOA ->PUPDR &= ~(1 << 12); //Pull Down in PA6 : 10
GPIOA ->PUPDR |= (1 << 13);
GPIOA ->AFR[0] |= 1 << 24; //PA6 is Alternate function 1: 0001

/**************************************************************************************/
//Configure TIM3
LcdInit();

RCC ->APB1ENR |= 1 << 1; //Enable clock for TIM3
TIM3 ->ARR = 0xFFFF;
TIM3 ->PSC = 0;
TIM3 ->CR1 |= 1 << 0; //Enable counter

TIM3 ->CCMR1 = 0x01; //01: CC1 channel is configured as input, IC1 is mapped on TI1
//IC1F: 0000 No filter, sampling is done at fDTS
//IC1PSC: Input capture 1 prescaler: 00 no prescaler, capture is done each time an edge is detected on the capture input
TIM3 ->CCER |= (1 << 0); //1: Capture enabled

/**************************************************************************************/

while(1)
{
TIM3 ->SR &= ~(1 << 1); //CLEAR Flag
while(!(TIM3 ->SR & (1 << 1))); //Wait a capture occurs

if(lock){
capt1 = TIM3 ->CCR1;
lock = 0;
}
else{
capt2 = TIM3 ->CCR1;

if(capt2 > capt1)
{
Freq = capt2 - capt1;
}
else{
Freq = ((0xffff-capt1)+capt2) +1;
}

Freq = (float)8000000.00/Freq;

//Print value in the LCD
LcdSendData(0x01, COMMAND_MODE); //Clear LCD
LcdSetCursor(1, 1);
LcdSendString("F=");
LcdPrintfloat(Freq);
LcdSendString("Hz");

lock = 1;
}

}
}

In debugging the code stuck here while(!(TIM3 ->SR & (1 << 1))); please any help?

Thank you.