stm32f4输入捕获测频率

在STM32F4系列微控制器中，输入捕获模式可以用于测量外部信号的频率。以下是实现该功能的步骤：

1. 配置GPIO引脚为输入模式，并使能对应的时钟。

2. 配置TIMx定时器的时钟和定时器模式。

3. 配置TIMx定时器的输入捕获模式和捕获通道。

4. 在捕获中断服务程序中读取捕获寄存器的值，并计算频率。

以下是一个基本的示例代码：

#include "stm32f4xx.h"

#define TIMx            TIM3
#define TIMx_CLK        RCC_APB1Periph_TIM3

#define TIMx_CH1_GPIO_PORT      GPIOC
#define TIMx_CH1_GPIO_PIN       GPIO_Pin_6
#define TIMx_CH1_GPIO_AF        GPIO_AF_TIM3
#define TIMx_CH1_GPIO_CLK       RCC_AHB1Periph_GPIOC

volatile uint32_t freq = 0;

void TIMx_Configuration(void)
{
    TIM_ICInitTypeDef TIM_ICInitStructure;
    GPIO_InitTypeDef GPIO_InitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

    RCC_APB1PeriphClockCmd(TIMx_CLK, ENABLE);
    RCC_AHB1PeriphClockCmd(TIMx_CH1_GPIO_CLK, ENABLE);

    GPIO_InitStructure.GPIO_Pin = TIMx_CH1_GPIO_PIN;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_Init(TIMx_CH1_GPIO_PORT, &GPIO_InitStructure);

    GPIO_PinAFConfig(TIMx_CH1_GPIO_PORT, GPIO_PinSource6, TIMx_CH1_GPIO_AF);

    TIM_TimeBaseStructure.TIM_Prescaler = 0;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseStructure.TIM_Period = 0xFFFFFFFF;
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseInit(TIMx, &TIM_TimeBaseStructure);

    TIM_ICInitStructure.TIM_Channel = TIM_Channel_1;
    TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising;
    TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
    TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;
    TIM_ICInitStructure.TIM_ICFilter = 0x0;
    TIM_ICInit(TIMx, &TIM_ICInitStructure);

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

    TIM_ITConfig(TIMx, TIM_IT_CC1, ENABLE);
    TIM_Cmd(TIMx, ENABLE);
}

void TIMx_IRQHandler(void)
{
    static uint32_t last_count = 0;
    static uint32_t current_count = 0;

    if (TIM_GetITStatus(TIMx, TIM_IT_CC1) != RESET)
    {
        TIM_ClearITPendingBit(TIMx, TIM_IT_CC1);
        last_count = current_count;
        current_count = TIM_GetCapture1(TIMx);
        freq = SystemCoreClock / (current_count - last_count);
    }
}

int main(void)
{
    TIMx_Configuration();

    while (1)
    {
        // do something
    }
}

在该示例代码中，使用TIM3定时器和GPIOC6引脚实现输入捕获模式。在TIMx_IRQHandler()中，使用TIM_GetCapture1()函数获取当前捕获寄存器的值，计算频率并保存到freq变量中。在主循环中可以通过访问freq变量来读取测量值。