给我写一个用stm32的hcsr04超声波模块测距代码

好的，以下是一个简单的使用STM32的HC-SR04超声波模块测距的代码，仅供参考：

#include "stm32f10x.h"
#include <stdio.h>
#include <stdbool.h>

#define TRIG_PIN GPIO_Pin_0
#define ECHO_PIN GPIO_Pin_1

volatile uint32_t pulse_start_time = 0;
volatile uint32_t pulse_end_time = 0;
volatile bool is_pulse_started = false;
volatile bool is_pulse_ended = false;

void delay(uint32_t ms) {
    while (ms--) {
        for (volatile int i = 0; i < 2000; i++);
    }
}

void init_gpio() {
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

    GPIO_InitTypeDef gpio_init;

    gpio_init.GPIO_Pin = TRIG_PIN;
    gpio_init.GPIO_Mode = GPIO_Mode_Out_PP;
    gpio_init.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &gpio_init);

    gpio_init.GPIO_Pin = ECHO_PIN;
    gpio_init.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_Init(GPIOA, &gpio_init);
}

void init_timer() {
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

    TIM_TimeBaseInitTypeDef tim_init;

    tim_init.TIM_Period = 0xFFFF;
    tim_init.TIM_Prescaler = 71;
    tim_init.TIM_ClockDivision = TIM_CKD_DIV1;
    tim_init.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM2, &tim_init);

    TIM_Cmd(TIM2, ENABLE);
}

void init_interrupt() {
    NVIC_InitTypeDef nvic_init;

    nvic_init.NVIC_IRQChannel = TIM2_IRQn;
    nvic_init.NVIC_IRQChannelPreemptionPriority = 0;
    nvic_init.NVIC_IRQChannelSubPriority = 0;
    nvic_init.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&nvic_init);

    TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);
}

void send_pulse() {
    GPIO_SetBits(GPIOA, TRIG_PIN);
    delay(10);
    GPIO_ResetBits(GPIOA, TRIG_PIN);
}

float get_distance() {
    send_pulse();
    while (!is_pulse_ended);
    float time_elapsed = (pulse_end_time - pulse_start_time) / 1000000.0;
    float distance = time_elapsed * 340.0 / 2.0;
    is_pulse_ended = false;
    return distance;
}

int main() {
    init_gpio();
    init_timer();
    init_interrupt();

    while (true) {
        float distance = get_distance();
        printf("Distance: %.2f cm\n", distance);
        delay(1000);
    }
}

void TIM2_IRQHandler() {
    if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET) {
        TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
        if (!is_pulse_started) {
            pulse_start_time = TIM_GetCounter(TIM2);
            is_pulse_started = true;
        }
        else {
            pulse_end_time = TIM_GetCounter(TIM2);
            is_pulse_ended = true;
            is_pulse_started = false;
        }
    }
}

这个代码使用了STM32的定时器TIM2来计时超声波的回响时间，通过测量回响时间来计算距离。其中，TRIG_PIN为超声波模块的触发引脚，ECHO_PIN为超声波模块的回响引脚。在main函数中不断调用get_distance函数来获取距离，并通过printf函数输出到串口上。在定时器中断中，记录下超声波触发和回响的时间戳，方便后续计算距离。