超声波

来源：互联网发布：手机版gps数据采集器编辑：程序博客网时间：2024/04/25 09:20

其实超声波贼简单，只是难者不会，会者不难而已。

核心就是先让Trig产生10+us的高电平，然后等待echo的出现高电平，开启定时器进行计数，完了关闭计数。计数对应的时间就是往返的时间。
乘以声速除以2就是距离。

不多说了，看代码一切理解。

#include <stdio.h>#include <reg51.h>#include <intrins.h>sbit echo = P2 ^ 1;//超声波测距的数据返回端口sbit trig = P2 ^ 0;//起始控制端口unsigned char flag = 0;unsigned int time=0;//计数float length;//返回距离unsigned char str[12];extern void InitLcd1602();extern void LcdShowStr(unsigned char x, unsigned char y, unsigned char *str);void LcdFullClear();void FloatToStr(unsigned char *str, float dat){    unsigned int H, L;    signed char i = 0;    unsigned char buf[12] = {0};    H = (unsigned int)dat;    L = dat*100-H*100;    do {          //先转换为低位在前的十进制数组        buf[i++] = H % 10;        H /= 10;    } while (H > 0);    while (i-- > 0)   //将数组值转换为ASCII码反向拷贝到接收指针上    {        *str++ = buf[i] + '0';    }    *str++ = '.';    *str++ = L/10 + '0';    *str++ = L%10 + '0';    *str = '\0';}void Init()//用于初始化设置定时器和串口波特率{    SCON = 0x50;    TH1 = 0xFD;    TL1 = 0xFD;//串口设置    TI = 1;    TR1 = 1; //开启定时器    TMOD = 0x21; //设T0为方式1    TH0 = 0;    TL0 = 0;    TR0 = 0;//定时器初始关闭    ET0 = 1; //允许T0中断    EA = 1; //开启总中断}void start_10() //10us+的起始信号{    int i;    trig = 1;    for (i = 0; i <= 13; i++)    {        _nop_();    }    trig = 0; //重新拉回低电平}void Count(void)//用于将时间换算成长度{    unsigned char str[12];    time = TH0 * 256 + TL0;    TH0 = 0;    TL0 = 0;    length = (time * 1.87)/100;     //算出来是CM    if(!flag)    {        //printf("%f\n",length);        FloatToStr(str, length);        LcdShowStr(2,0, str);    }    else    {        flag = 0;        //printf("error\n");        LcdShowStr(2,0, "error");    }}void Delay500ms()       //@11.0592MHz{    unsigned char i, j, k;    i = 22;    j = 3;    k = 227;    do    {        do        {            while (--k);        } while (--j);    } while (--i);}void Scan(){    start_10();    while (!echo);    //当RX为零时等待    TR0 = 1; //开启计数    while (echo);    //当RX为1计数并等待    TR0 = 0; //关闭计数    Count();//计算出距离    Delay500ms();    LcdFullClear();}void main(){    Init();//定时器初始化    InitLcd1602();    while(1)    {        Scan();     }}void Timer0() interrupt 1{    flag = 1;}

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