STM32F4 Discovery. Question about input capture mode

Question

Programming

Hello,

please tell me what I'm doing wrong.
The task is to read the pulse width.
After googling, I decided to use the Input capture mode for the timer.
The result is this code:

#include "stm32f4xx.h"
#include <stm32f4xx_rcc.h>
#include <stm32f4xx_gpio.h>
#include <stm32f4xx_tim.h>
#include <misc.h>
#include "lcd.hpp"
#include "stdio.h"

volatile int IC3ReadValue1 = 0;
volatile int IC3ReadValue2 = 0;
volatile int Capture = 0;
volatile int CaptureNumber = 0;
volatile int dataCaptureReady = 0;

void tim3ConfigRising()
{

  TIM_ICInitTypeDef timICStruct;

  timICStruct.TIM_Channel = TIM_Channel_2;
  timICStruct.TIM_ICPolarity = TIM_ICPolarity_Rising;
  timICStruct.TIM_ICSelection = TIM_ICSelection_DirectTI;
  timICStruct.TIM_ICPrescaler = TIM_ICPSC_DIV1;
  timICStruct.TIM_ICFilter = 0x0;

  TIM_ICInit(TIM3, &timICStruct);

}

void tim3ConfigFalling()
{
  TIM_ICInitTypeDef timICStruct;

  timICStruct.TIM_Channel = TIM_Channel_2;
  timICStruct.TIM_ICPolarity = TIM_ICPolarity_Falling;
  timICStruct.TIM_ICSelection = TIM_ICSelection_DirectTI;
  timICStruct.TIM_ICPrescaler = TIM_ICPSC_DIV1;
  timICStruct.TIM_ICFilter = 0x0;

  TIM_ICInit(TIM3, &timICStruct);

}

void initTimers()
{
   RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

    /* Частота счёта - 10 мкс, период - 20 мс */
   TIM_TimeBaseInitTypeDef base_timer;
   TIM_TimeBaseStructInit(&base_timer);
   base_timer.TIM_Prescaler = SystemCoreClock / 1000 - 1;
   base_timer.TIM_Period = 2000;
   base_timer.TIM_ClockDivision = 0;
   base_timer.TIM_CounterMode = TIM_CounterMode_Up;
   TIM_TimeBaseInit(TIM3, &base_timer);

   tim3ConfigRising();

   // TIM enable counter
  	 TIM_Cmd(TIM3, ENABLE);

   // Enable the CC2 Interrupt Request
   TIM_ITConfig(TIM3, TIM_IT_CC2, ENABLE);

   NVIC_InitTypeDef NVIC_InitStructure;

   NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
   NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
   NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
   NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
   NVIC_Init(&NVIC_InitStructure);
}

void initGpio()
{
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

  GPIO_InitTypeDef gpioStruct;
  gpioStruct.GPIO_Mode = GPIO_Mode_IN;
  gpioStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
  gpioStruct.GPIO_Speed = GPIO_Speed_50MHz;
  gpioStruct.GPIO_Pin = GPIO_Pin_7;

  GPIO_Init(GPIOA, &gpioStruct);
}

int main(void)
{

  LiquidCrystal lcd(RCC_AHB1Periph_GPIOC, GPIOC, GPIO_Pin_0, GPIO_Pin_1, GPIO_Pin_2,
      RCC_AHB1Periph_GPIOC, GPIOC, GPIO_Pin_5, GPIO_Pin_4);

  initGpio();
  initTimers();

  char buffer[20];
  char *bufPtr;
  bufPtr = (char*)buffer;
  while(1)
  {

    if (dataCaptureReady)
    {
      /* Capture computation */
        if (IC3ReadValue2 > IC3ReadValue1)
        {
        Capture = (IC3ReadValue2 - IC3ReadValue1);
        }
        else
        {
        Capture = ((0xFFFF - IC3ReadValue1) + IC3ReadValue2);
        }
        /* Frequency computation */
        int TIM3Freq = (uint32_t) SystemCoreClock / Capture;

      dataCaptureReady = 0;
      sprintf(bufPtr, "%d %d", Capture, TIM3Freq);
      lcd.setCursor(0,0);
      lcd.print(bufPtr);
    }

  }

}

extern "C" {
  void TIM3_IRQHandler()
  {

    if(TIM_GetITStatus(TIM3, TIM_IT_CC2) == SET)
    {
      /* Clear TIM3 Capture compare interrupt pending bit */
      TIM_ClearITPendingBit(TIM3, TIM_IT_CC2);
      if(CaptureNumber == 0)
      {
        /* Get the Input Capture value */
        IC3ReadValue1 = TIM_GetCapture2(TIM3);
        CaptureNumber = 1;

        tim3ConfigFalling();

      }
      else if(CaptureNumber == 1)
      {
        /* Get the Input Capture value */
        IC3ReadValue2 = TIM_GetCapture2(TIM3);

        dataCaptureReady = 1;
        CaptureNumber = 0;

        tim3ConfigRising();

      }
    }
  }
}

But, the stone flower does not come out.
The interrupt handler is not called, the TIM3->CCR2 register is empty, while everything is as expected in GPIOA->IDR.

There is an assumption that the PA07 pin is not “connected” to the timer and this does not cause an interrupt, but the solution has not yet been found

Answer 1

Yes, that's right. Pin PA07 is not related to the timer, because this is its alternative function, which must be enabled.

gpioStruct.GPIO_Mode = GPIO_Mode_AF;
GPIO_PinAFConfig(GPIOC, GPIO_PinSource6, GPIO_AF_TIM3);