基于C8051单片机超声波测距电平触发编写（留底）

#include <c8051f020.h>  
#include <intrins.h>
#define uchar unsigned char
#define uint unsigned int
void SYSCLK_Init (void);
void PORT_Init (void); 
void  StartModule() ;
void display(unsigned char bai,unsigned char shi,unsigned char ge);
void delay(unsigned int z);
void timerinit();
void delay(unsigned int z);
void Timer_Count(void);
unsigned int  time=0;
uchar i;
 uchar j;
unsigned long S=0;
unsigned char qian,bai,shi,ge;
bit flag =0;
sbit lcdrs=P2^5;
sbit lcden=P2^7;
sbit lcdwr=P2^6;
sbit  RX = P0^1;
sbit  TX = P0^0;
uchar abc[]={0x30,0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,0x39};   //1234567;
uchar result[3];
void delay(void)
{
 int a=10000;
 while(a!=0)
 {
  a--;
 }
}
void write_com(uchar com)
{
 lcdrs=0;
 P3=com;
 delay();
 lcden=1;
 delay();
 lcden=0;
}
void write_date(uchar dat)
{
 lcdrs=1;
 P3=dat;
 delay();
 lcden=1;
 delay();
 lcden=0;
}
void init()
{
 lcdwr=0;
 lcden=0;
 write_com(0x38);
 write_com(0x0c);
 write_com(0x06);
 write_com(0x01);
}
void main()
{
 unsigned int valA;
  WDTCN = 0xde;
  WDTCN = 0xad; 
  timerinit();                      
  SYSCLK_Init ();                                                                 
  PORT_Init ();                        
 init();
 lcdrs=0;
 lcdwr=0;
 write_com(0x40);
while(1)
{    
RX=1;
StartModule();
 
for(valA=100;valA>0;valA--)
{
   if(RX==1)
   {
       Timer_Count();
   }
}
}
}
 void SYSCLK_Init (void)
{
   OSCICN = 0x05;                                                                                  
}
 void PORT_Init (void)
{
   XBR0    = 0x04;                     // Enable UART0
   XBR1    = 0x00;
   XBR2    = 0x40;                     // Enable crossbar and weak pull-ups
  P0MDOUT |= 0xff;                    // enable TX0 as a push-pull output
   P2MDOUT  = 0xe0;                    // P2口设为推挽方式
   P3MDOUT  = 0xff;                    // P2口设为推挽方式      
}
void Conut(void)
 {
  time=TH0*256+TL0;
  TH0=0;
  TL0=0;
  S=(uint)(time*1.7*1.6*1.5)/10;     //算出来是MM
  if((S>=7000)||flag==1) //超出测量范围显示“-”
  { 
   flag=0;
   display(0x80,0x80,0x80);
  }
  else
  {
   bai=S/100;
   shi=S%100/10;
   ge=S%10;
   display(bai,shi,ge);
  }
 }
void zd0() interrupt 1    //T0中断用来计数器溢出,超过测距范围
  {
    flag=1;        //中断溢出标志
 RX=0;
  }
void  StartModule()            //启动模块
  {
   TX=1;                        //启动一次模块
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
/*   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();*/
   TX=0;
  }
void Timer_Count(void)
{
   TR0=1;       //开启计数
      while(RX);   //当RX为1计数并等待
      TR0=0;    //关闭计数
 
         Conut();   //计算
}
void timerinit()
{
 TMOD=0x01;     //设T0为方式1，GATE=1；
 TH0=0;
 TL0=0;         
 ET0=1;             //允许T0中断
 EA=1;      //开启总中断   
}
/*********************************************************/
void display(unsigned char bai,unsigned char shi,unsigned char ge)
{ 
  
     uchar i;
  result[0]=abc[bai];
  result[1]=abc[shi];
  result[2]=abc[ge];
   write_com(0x40);
     for(i=0;i<3;i++)
  {
  write_com(0x80+i+1);
  write_date(result[i])  ;
  }
}

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