/*******超声波测距程序*******/
#include 
#include

#define uchar unsigned char
#define uint unsigned int

sbit rs = P2^4;
sbit rw = P2^5;
sbit en = P2^6;
sbit tr = P3^2;                
sbit ec = P1^0;  

uint distance = 0;            
uchar count;

void delayms(uint x)
{
   uint i,j;
   for(i=x;i>0;i--)
     for(j=110;j>0;j--);
}
void write_com(uchar com)
{
   rs = 0;
   rw = 0;
   en = 0;
   P0 = com;
   delayms(2);
   en = 1;
   delayms(5);
   en = 0;
   delayms(2);
}
void write_dat(uchar dat)
{
   rs = 1;
   rw = 0;
   en = 0;
   P0 = dat;
   delayms(2);
   en = 1;
   delayms(5);
   en = 0;
   delayms(2);
}
void Init_1602()
{
write_com(0x38);
delayms(5);
write_com(0x0c);
delayms(5);
write_com(0x06);
delayms(5);
write_com(0x01);
delayms(5);
}
void Init_TIMER0()
{
TMOD = 0x01;  
  TL0 = 0x66;
TH0 = 0xfc;     
  ET0 = 1;       
EA = 1;        
}
void Init_mk()
{
tr =1;
  ec = 1;
count = 0;
distance = 0;
}
void init_fs()
{
  ec= 1;
_nop_();
_nop_();
_nop_();
_nop_();
_nop_();
_nop_();
_nop_();
_nop_();
_nop_();
_nop_();
_nop_();
_nop_();
_nop_();
_nop_();
_nop_();
  ec = 0;
}
void jsdistance()
{
uint y;
TR0 = 1;
while(tr);
TR0 = 0;
y = TH0*256+TL0;
y = y - 0xfc66;
distance = y + 1000 * count;
TL0 = 0x66;
TH0 = 0xfc;
delayms(30);
distance = 0.340 * distance / 2;
} 
void display()
{
  uchar qian,bai,shi,ge;
  qian= (distance / 1000);
  bai= (distance  / 100) % 10;
  shi = (distance  / 10) % 10;
  ge = distance  % 10;
   write_com(0x80+0x40+4);
  write_dat(0x30+qian);
  write_dat(0x30+bai);
   write_dat(0x30+shi);
  write_dat('.');
  write_dat(0x30+ge);
  write_dat('C');           
  write_dat('M');   
}
void write_hz(uchar *p)
{
   while(*p != 0)
   write_dat(*p++);
   delayms(500);
}
void main()
{ 
  rw = 0;
Init_1602();
Init_TIMER0();
Init_mk();
while(1)
{
   init_fs();        
   while(tr == 0)          
         {
             ;
         }
   jsdistance();    
   display();
   Init_mk();          
   delayms(10);   
     write_com(0x80);
     write_hz("****distance****");     
  } 
}
void TIMER0() interrupt 1
{
TF0 = 0;
TL0 = 0x66;
TH0 = 0xfc;
count++;
if(count == 18)
{
  TR0 =0;
   TL0 = 0x66;
   TH0 = 0xfc;
  count = 0;
}
}