int ping(){
   int dis;
    dis=0;
      trisb.f0=0;
     portb.f0=0;
     portb.f0=1;
     Delay_us(5);
     portb.f0=0;
     trisb.f0=1;
     portb.f0=0;
     while(portb.f0==0){}
      while(portb.f0==1){
dis++;

        Delay_us(1);
      }
      dis=dis/29/2;
      return dis;  //distance in cm
}