基于stm32f103rct6的超声波测距代码

以下是基于STM32F103RCT6的超声波测距代码，使用的是TIM2模块作为计时器：

#include "stm32f10x.h"

#define TRIG_PIN GPIO_Pin_8
#define ECHO_PIN GPIO_Pin_9

void GPIO_Configuration(void);
void TIM_Configuration(void);

int main(void)
{
    uint32_t distance;
    GPIO_Configuration();
    TIM_Configuration();

    while(1)
    {
        GPIO_SetBits(GPIOB, TRIG_PIN);
        delay_us(10);
        GPIO_ResetBits(GPIOB, TRIG_PIN);
        while(!GPIO_ReadInputDataBit(GPIOB, ECHO_PIN));
        TIM_Cmd(TIM2, ENABLE);
        while(GPIO_ReadInputDataBit(GPIOB, ECHO_PIN));
        TIM_Cmd(TIM2, DISABLE);
        distance = TIM_GetCounter(TIM2) / 58;
        TIM_SetCounter(TIM2, 0);
    }
}

void GPIO_Configuration(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);

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

    GPIO_InitStructure.GPIO_Pin = ECHO_PIN;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
    GPIO_Init(GPIOB, &GPIO_InitStructure);
}

void TIM_Configuration(void)
{
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

    TIM_TimeBaseStructure.TIM_Period = 0xFFFF;
    TIM_TimeBaseStructure.TIM_Prescaler = SystemCoreClock / 1000000 - 1;
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
}

其中，`delay_us()`函数可以自己定义，实现微秒级延时。这段代码实现的是不断地进行超声波测距，每次测量完成后将距离存储在`distance`变量中。具体的超声波测距原理可以参考其他资料。