用stm32实现五路循迹模块的功能，控制小车循迹的代码

循迹模块一般使用红外线传感器，可以检测黑线和白线的反差，从而实现对小车行驶方向的控制。以下是使用STM32实现五路循迹的代码示例：

#include "stm32f10x.h"

#define Trig1 GPIO_Pin_0
#define Echo1 GPIO_Pin_1
#define Trig2 GPIO_Pin_2
#define Echo2 GPIO_Pin_3
#define Trig3 GPIO_Pin_4
#define Echo3 GPIO_Pin_5
#define Trig4 GPIO_Pin_6
#define Echo4 GPIO_Pin_7
#define Trig5 GPIO_Pin_8
#define Echo5 GPIO_Pin_9

void delay_us(u32 n)
{
    u32 i;
    while(n--)
    {
        i = 10;
        while(i--);
    }
}

void Ultrasonic_Init(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
    TIM_ICInitTypeDef TIM_ICInitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB | RCC_APB2Periph_AFIO, ENABLE);
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

    GPIO_InitStructure.GPIO_Pin = Trig1 | Trig2 | Trig3 | Trig4 | Trig5;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    GPIO_InitStructure.GPIO_Pin = Echo1 | Echo2 | Echo3 | Echo4 | Echo5;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOB, &GPIO_InitStructure);

    TIM_TimeBaseInitStructure.TIM_Period = 0xFFFF;
    TIM_TimeBaseInitStructure.TIM_Prescaler = 72 - 1;
    TIM_TimeBaseInitStructure.TIM_ClockDivision = 0;
    TIM_TimeBaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM3, &TIM_TimeBaseInitStructure);

    TIM_ICInitStructure.TIM_Channel = TIM_Channel_1;
    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 = 0;
    TIM_ICInit(TIM3, &TIM_ICInitStructure);

    TIM_ICInitStructure.TIM_Channel = TIM_Channel_2;
    TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Falling;
    TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_IndirectTI;
    TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;
    TIM_ICInitStructure.TIM_ICFilter = 0;
    TIM_ICInit(TIM3, &TIM_ICInitStructure);

    TIM_ITConfig(TIM3, TIM_IT_CC1 | TIM_IT_CC2, ENABLE);
    TIM_Cmd(TIM3, ENABLE);

    NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
}

void Ultrasonic_Trigger(u16 GPIO_Pin)
{
    GPIO_SetBits(GPIOA, GPIO_Pin);
    delay_us(10);
    GPIO_ResetBits(GPIOA, GPIO_Pin);
}

u16 Ultrasonic_GetDistance(u16 GPIO_Pin)
{
    u16 distance = 0;
    u32 counter = 0;
    TIM3->CNT = 0;
    Ultrasonic_Trigger(GPIO_Pin);
    while(GPIO_ReadInputDataBit(GPIOB, GPIO_Pin) == RESET);
    TIM_Cmd(TIM3, ENABLE);
    while(GPIO_ReadInputDataBit(GPIOB, GPIO_Pin) == SET)
    {
        counter++;
        if(counter > 60000) break;
    }
    TIM_Cmd(TIM3, DISABLE);
    distance = (float)counter / 58.0;
    return distance;
}

int main(void)
{
    u16 distance[5];
    Ultrasonic_Init();
    while(1)
    {
        distance[0] = Ultrasonic_GetDistance(Echo1);
        distance[1] = Ultrasonic_GetDistance(Echo2);
        distance[2] = Ultrasonic_GetDistance(Echo3);
        distance[3] = Ultrasonic_GetDistance(Echo4);
        distance[4] = Ultrasonic_GetDistance(Echo5);

        if(distance[0] > 10 && distance[0] < 30) //左前
        {
            //向右转
        }
        else if(distance[1] > 10 && distance[1] < 30) //左
        {
            //向右转
        }
        else if(distance[2] > 10 && distance[2] < 30) //中
        {
            //直行
        }
        else if(distance[3] > 10 && distance[3] < 30) //右
        {
            //向左转
        }
        else if(distance[4] > 10 && distance[4] < 30) //右前
        {
            //向左转
        }
        else //没有检测到黑线
        {
            //停止
        }
    }
}

以上代码中，使用了定时器TIM3作为超声波模块的计时器，通过捕获定时器的计数值来计算超声波的回波时间，并进而计算出距离。通过检测五路超声波模块返回的距离来判断小车的行驶方向，从而实现对小车的控制。