写一个stm32F103C8T6超声波测距代码

以下是一个基本的超声波测距代码，适用于STM32F103C8T6单片机。

首先，需要定义一些宏和变量：

#define TRIG_PIN GPIO_Pin_0
#define ECHO_PIN GPIO_Pin_1
#define TRIG_PORT GPIOA
#define ECHO_PORT GPIOA

volatile uint32_t pulse_start = 0;
volatile uint32_t pulse_end = 0;
volatile uint32_t pulse_duration = 0;
volatile uint32_t distance = 0;

接下来，需要进行GPIO的初始化：

void GPIO_Init(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

    GPIO_InitStructure.GPIO_Pin = TRIG_PIN;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(TRIG_PORT, &GPIO_InitStructure);

    GPIO_InitStructure.GPIO_Pin = ECHO_PIN;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(ECHO_PORT, &GPIO_InitStructure);
}

然后，需要编写触发超声波脉冲的函数：

void send_pulse(void)
{
    GPIO_SetBits(TRIG_PORT, TRIG_PIN);
    delay_us(10);
    GPIO_ResetBits(TRIG_PORT, TRIG_PIN);
}

接下来，需要编写中断服务程序来处理回声信号：

void EXTI1_IRQHandler(void)
{
    if (EXTI_GetITStatus(EXTI_Line1) != RESET)
    {
        if (GPIO_ReadInputDataBit(ECHO_PORT, ECHO_PIN) == SET)
        {
            pulse_start = TIM_GetCounter(TIM2);
        }
        else
        {
            pulse_end = TIM_GetCounter(TIM2);
            pulse_duration = pulse_end - pulse_start;
            distance = pulse_duration * 0.034 / 2;
        }

        EXTI_ClearITPendingBit(EXTI_Line1);
    }
}

最后，在主函数中初始化GPIO、定时器和中断，并在循环中触发超声波脉冲：

int main(void)
{
    // 初始化GPIO
    GPIO_Init();

    // 初始化定时器
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
    TIM_TimeBaseStructure.TIM_Period = 65535;
    TIM_TimeBaseStructure.TIM_Prescaler = 72 - 1;
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

    // 初始化中断
    EXTI_InitTypeDef EXTI_InitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
    GPIO_EXTILineConfig(GPIO_PortSourceGPIOA, GPIO_PinSource1);
    EXTI_InitStructure.EXTI_Line = EXTI_Line1;
    EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
    EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising_Falling;
    EXTI_InitStructure.EXTI_LineCmd = ENABLE;
    EXTI_Init(&EXTI_InitStructure);
    NVIC_InitStructure.NVIC_IRQChannel = EXTI1_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x00;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x00;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

    // 启动定时器
    TIM_Cmd(TIM2, ENABLE);

    while (1)
    {
        send_pulse();
        delay_ms(500);
    }
}

希望这个代码可以帮助到你！