51 Ultrasonic Distance Measurement

#include "Reg51.h" #include <intrins.h> sbit rx=p2^1;
Sbit tx=p2^0;
unsigned int time=0;
unsigned int timer=0;
unsigned char posit=0;
unsigned long s=0;
Bit flag = 0;
--¶¨òåê¹óãµäio--//#define Gpio_dig P0 sbit lsa=p2^2;
Sbit lsb=p2^3;

Sbit lsc=p2^4; --¶¨òå諾ö±äá¿--//unsigned char code dig_code[17]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07, 0x7f,0x6f,0x77,0x7c,
0X39,0X5E,0X79,0X71};
0¡¢1¡¢2¡¢3¡¢4¡¢5¡¢6¡¢7¡¢8¡¢9¡¢a¡¢b¡¢c¡¢d¡¢e¡¢fµäïôê¾âëunsigned Char disbuff[4] ={0,0,0,0,}; /******************************************************************************* *º¯êýãû: DigDisplay *º¯êý¹¦ä ü:ê¹óãêýâë¹üïôê¾*êäèë:îþ*êä³ö:îþ***************************************************
	/void Digdisplay () {unsigned char i;
	unsigned int J; for (i=0;i<8;i++) {switch (i)//î»ñ¡£¬ñ¡ôñµãááµäêýâë¹ü£¬{case (0): lsa=0; lsb=0; lsc=0; Break;//ïôê¾µú0î»case (1): lsa=1; lsb=0; lsc=0; Break;//ïôê¾µú1î»case (2): lsa=0; Lsb=1; lsc=0; Break;//ïôê¾µú2î»case (3): lsa=1; Lsb=1; lsc=0; Break;//ïôê¾µú3î»case (4): lsa=0; lsb=0; Lsc=1; Break;//ïôê¾µú4î»case (5): lsa=1; lsb=0; Lsc=1; Break;//ïôê¾µú5î»case (6): lsa=0; Lsb=1; Lsc=1; Break;//ïôê¾µú6î»case (7): lsa=1; Lsb=1; Lsc=1;						 break;//ïôê¾µú7î»} gpio_dig=disbuff[i];//¢ëí¶îâëj=10;	
		ɨãè¼ä¸ôê±¼äé趨while (j--); Gpio_dig=0x00;//ïûòþ}}/********************************************************/void Conut (void) {time=TH0*25
	 6+tl0;
	 th0=0;
	
	 tl0=0;     S= (Long) (time*0.17); ëã³öà´êçcm if ((s>=4000) | |
	  flag==1)//³¬³ö²âῶî§ïô꾡°err0¡±{flag=0;	   disbuff[0]=0x3f;	   ¡°-¡±disbuff[1]=0x50;	   ¡°-¡±disbuff[2]=0x50;	   ¡°-¡±disbuff[3]=0x79;
	  ¡°-¡±} else {disbuff[3]=dig_code[s%10000/1000];
	  DISBUFF[2]=DIG_CODE[S%1000/100];
	  DISBUFF[1]=DIG_CODE[S%100/10];
	 DISBUFF[0]=DIG_CODE[S%10/1]; }
	}
/**************************************/void Zd0 () Interrupt 1//t0öð¶ïóãà´¼æêýæ÷òç³ö,³¬¹ý²â¾à ¶î§{flag=1; Öð¶ïòç³ö±êö¾}/********************************************************/void Zd3 () Interrupt 3 {TH1=0XF
	 8;
	 tl1=0x30;
	 Digdisplay ();
	 timer++;
	  if (timer>=100) {timer=0;			                Tx=1; 
	  800MS Start a module _nop_ (); 
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ ();
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ (); 
	  _nop_ ();
	  _nop_ ();
	 tx=0;		   
	}}/*********************************************************/void Main (void) {tmod=0x11;
	th0=0;          
	tl0=0;		   
	Th1=0xf8;
	tl1=0x30;            
	Et0=1;			   
	Et1=1;			  
	Tr1=1;			   

	Ea=1; while (1) {while (!		RX);			 No ultrasound detected, RX is low level tr0=1;		Timer 0 is used to prevent the distance is too long, the number is too large to display, make a limit while (RX);
	 An ultrasonic wave is detected, which calculates the distance based on the time difference.tr0=0;			
	Conut (); }

  }