stm32f407捕获方波

以下是使用STM32F407捕获方波的示例代码：

#include "stm32f4xx.h"

#define TIMER_FREQ 84000000

int main(void)
{
  // 初始化GPIO
  GPIO_InitTypeDef GPIO_InitStruct;
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
  GPIO_InitStruct.GPIO_Pin = GPIO_Pin_0;
  GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStruct.GPIO_Speed = GPIO_Speed_100MHz;
  GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_Init(GPIOA, &GPIO_InitStruct);

  // 将GPIO引脚与定时器功能映射
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource0, GPIO_AF_TIM2);

  // 初始化定时器
  TIM_TimeBaseInitTypeDef TIM_TimeBaseStruct;
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
  TIM_TimeBaseStruct.TIM_Period = 65535;
  TIM_TimeBaseStruct.TIM_Prescaler = ((SystemCoreClock / 2) / TIMER_FREQ) - 1;
  TIM_TimeBaseStruct.TIM_ClockDivision = 0;
  TIM_TimeBaseStruct.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseStruct.TIM_RepetitionCounter = 0;
  TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStruct);

  // 配置定时器输入捕获模式
  TIM_ICInitTypeDef TIM_ICInitStruct;
  TIM_ICInitStruct.TIM_Channel = TIM_Channel_1;
  TIM_ICInitStruct.TIM_ICPolarity = TIM_ICPolarity_Rising;
  TIM_ICInitStruct.TIM_ICSelection = TIM_ICSelection_DirectTI;
  TIM_ICInitStruct.TIM_ICPrescaler = TIM_ICPSC_DIV1;
  TIM_ICInitStruct.TIM_ICFilter = 0x0;
  TIM_ICInit(TIM2, &TIM_ICInitStruct);

  // 启动定时器
  TIM_Cmd(TIM2, ENABLE);

  // 等待捕获到方波
  while (1) {
    if (TIM_GetFlagStatus(TIM2, TIM_FLAG_CC1) != RESET) {
      uint16_t capture_value = TIM_GetCapture1(TIM2);
      float frequency = (float)TIMER_FREQ / (float)(capture_value + 1);
      TIM_ClearFlag(TIM2, TIM_FLAG_CC1);
    }
  }

  return 0;
}

该代码将PA0引脚与TIM2的CH1功能相连，并使用输入捕获模式来捕获方波的频率。在捕获到方波后，程序会计算出方波的频率并输出到控制台。需要注意的是，在使用输入捕获模式时，需要在启动定时器前配置输入捕获模式。