超声波测距代码：

#include<reg52.h>sbit echo=P2^0 ; //回声接收端口
sbit trig=P2^1  ;//超声波触发端口sbit wei1=P2^4;
sbit wei2=P2^5;
sbit wei3=P2^6;
sbit wei4=P2^7;sbit in=P2^2;#define dula P0
#define uchar unsigned char
#define uint unsigned intlong int distance=0;
uchar count;
unsigned char code table[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};
unsigned char code table1[]={0xbf,0x86,0xdb,0xcf,0xe6,0xed,0xfd,0x87,0xff,0xef,0x71};void delay(uint xms)
{uint i,j;for(i=xms;i>0;i--)for(j=112;j>0;j--);
}void display(long int num)
{uchar qian,bai,shi,ge;if((num>5000)||(num==0)){qian=15;bai=15;shi=10;ge=15;}else{qian=num/1000;bai=(num/100)%10;shi=(num/10)%10;ge=num%10;if(bai>0){in=0;}else if(bai==0){in=1;}}wei1=1;wei2=0;wei3=0;wei4=0;P0=table[qian];delay(2);wei1=0;wei2=1;wei3=0;wei4=0;P0=table[bai];delay(2);wei1=0;wei2=0;wei3=1;wei4=0;P0=table1[shi];delay(2);wei1=0;wei2=0;wei3=0;wei4=1;P0=table[ge];delay(2);
}void Init_timer0(void)
{TMOD=0x01;TL0=0x66;TH0=0xfc;ET0=1;EA=1;
}void Init_parameter(void)
{echo=0;trig=0;count=0;distance=0;
}void Trig_SuperSonic(void) //发出声波
{trig=1;delay(1);trig=0;
}void Measure_Distance(void)
{uchar l;uint h,y;TR0=1;while(echo){;}TR0=0;l=TL0;h=TH0;y=(h<<8)+1;y=y-0xfc66;distance=y+1000*count;TL0=0x66;TH0=0xfc;delay(30);distance=0.17*distance;
}void main(void)
{uchar a;Init_timer0();Init_parameter();while(1){Trig_SuperSonic();while(echo==0){;}Measure_Distance();for(a=100;a>0;a--){display(distance);}Init_parameter();}
}void timer0(void)interrupt 1
{TF0=0;TL0=0x66;TH0=0xfc;count++;if(count==18){TR0=0;TL0=0x66;TH0=0xfc;count=0;}
}