C51单片机超声波传感器测距

#include<stc15.h>
#include<intrins.h> //选择内部晶振 27MHZ
#define uchar unsigned char  
#define uint  unsigned int
sbit  IN1_= P0^0;
sbit  IN2_= P0^1;//左前轮
sbit  IN3_= P0^2;
sbit  IN4_= P0^3;//右前轮

sbit  IN1= P1^0;
sbit  IN2= P1^1;//左后轮
sbit  IN3= P1^2;
sbit  IN4= P1^3;//右后轮
sbit   bee=P4^1;

sbit Echo=P3^2;  

sbit Trig=P1^5;

bit flag=0;

void Delay5us()

{  uchar i;  i--;  i--;  i--;  i--;  i--;  i--; }
void delay(int i)
{
while(i--);
}

void Init()