stm32f407 hc-sr04超声波测距代码

以下是使用STM32F407和HC-SR04超声波测距模块的示例代码：

#include "stm32f4xx.h"
#include "stm32f4xx_gpio.h"
#include "stm32f4xx_rcc.h"
#include "stm32f4xx_tim.h"
#include "misc.h"

#define TRIG_PIN GPIO_Pin_0
#define ECHO_PIN GPIO_Pin_1
#define GPIO_PORT GPIOA

uint32_t distance = 0;

void GPIO_Configuration(void) {
    GPIO_InitTypeDef GPIO_InitStructure;
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

    GPIO_InitStructure.GPIO_Pin = TRIG_PIN;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
    GPIO_Init(GPIO_PORT, &GPIO_InitStructure);

    GPIO_InitStructure.GPIO_Pin = ECHO_PIN;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
    GPIO_Init(GPIO_PORT, &GPIO_InitStructure);
}

void TIM_Configuration(void) {
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

    TIM_TimeBaseStructure.TIM_Period = 0xFFFFFFFF;
    TIM_TimeBaseStructure.TIM_Prescaler = (uint16_t)(SystemCoreClock / 1000000) - 1;
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

    TIM_ICInitTypeDef TIM_ICInitStructure;
    TIM_ICInitStructure.TIM_Channel = TIM_Channel_2;
    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(TIM2, &TIM_ICInitStructure);

    TIM_Cmd(TIM2, ENABLE);
}

uint32_t GetDistance(void) {
    GPIO_SetBits(GPIO_PORT, TRIG_PIN);
    Delay_us(10);
    GPIO_ResetBits(GPIO_PORT, TRIG_PIN);

    uint32_t start_time = 0;
    uint32_t end_time = 0;
    uint32_t timeout = 0;

    while (GPIO_ReadInputDataBit(GPIO_PORT, ECHO_PIN) == RESET) {
        if (++timeout > 1000000) {
            return 0xFFFFFFFF;
        }
    }

    start_time = TIM_GetCounter(TIM2);
    timeout = 0;

    while (GPIO_ReadInputDataBit(GPIO_PORT, ECHO_PIN) == SET) {
        if (++timeout > 1000000) {
            return 0xFFFFFFFF;
        }
    }

    end_time = TIM_GetCounter(TIM2);

    if (end_time > start_time) {
        distance = (end_time - start_time) * 10 / 58;
    } else {
        distance = (start_time - end_time) * 10 / 58;
    }

    return distance;
}

int main(void) {
    GPIO_Configuration();
    TIM_Configuration();

    while (1) {
        GetDistance();
    }

    return 0;
}

此代码初始化GPIO和定时器，然后在主循环中调用`GetDistance()`函数来获取测量到的距离。该函数使用超声波模块发送一个10微秒的脉冲，然后等待接收到回波。通过测量回波的时间来计算距离，并返回结果。在本例中，距离以毫米为单位表示。如果无法检测到回波或测量超时，则返回0xFFFFFFFF。

需要注意的是，在本例中，我们使用了定时器的输入捕获模式来测量回波的时间。我们使用TIM2的通道2来读取ECHO引脚的状态，并在上升沿触发捕获。此代码假设您已正确配置STM32F407的时钟源。如果您遇到问题，请参阅STM32F407参考手册。