STM32超声波计数代码

以下是一个基于STM32的超声波计数代码示例，使用的是STM32F103C8T6开发板和HC-SR04超声波传感器。

#include "stm32f10x.h"
#include "stdio.h"

#define TRIG_PIN GPIO_Pin_0
#define ECHO_PIN GPIO_Pin_1

void delay_us(uint32_t us)
{
    uint32_t count = us * 8;
    while(count--);
}

void TIM2_init(void)
{
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    NVIC_InitTypeDef NVIC_InitStructure;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

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

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

    TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
    TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);

    TIM_Cmd(TIM2, ENABLE);
}

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(GPIOA, &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(GPIOA, &GPIO_InitStructure);
}

void TIM2_IRQHandler(void)
{
    static uint16_t overflow_cnt = 0;
    static uint32_t last_capture_time = 0;
    static uint32_t current_capture_time = 0;
    static uint32_t pulse_width = 0;

    if(TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
    {
        overflow_cnt++;
        TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
    }

    if(GPIO_ReadInputDataBit(GPIOA, ECHO_PIN) == SET)
    {
        TIM_SetCounter(TIM2, 0);
        overflow_cnt = 0;
    }

    if(GPIO_ReadInputDataBit(GPIOA, ECHO_PIN) == RESET && overflow_cnt > 0)
    {
        current_capture_time = TIM_GetCounter(TIM2) + overflow_cnt * 0xFFFF;
        pulse_width = current_capture_time - last_capture_time;
        last_capture_time = current_capture_time;
        overflow_cnt = 0;
    }
}

int main(void)
{
    uint32_t distance = 0;
    char buf[10];

    GPIO_init();
    TIM2_init();

    while(1)
    {
        GPIO_SetBits(GPIOA, TRIG_PIN);
        delay_us(10);
        GPIO_ResetBits(GPIOA, TRIG_PIN);

        delay_us(60000);

        distance = pulse_width / 58;
        sprintf(buf, "%d cm\n", distance);
        USART_SendString(USART1, buf);
    }
}

代码中使用TIM2用作计时器，GPIOA的0号引脚用作超声波发射端口，GPIOA的1号引脚用作超声波接收端口。当超声波发射端口发出超声波时，计时器开始计时，当超声波接收端口接收到超声波时，计时器停止计时，计算超声波从发射到接收的时间差，进而计算出距离。最后将距离发送到串口调试助手中显示出来。