ping		con	0		' Set the number to free pin '0' Output to activate pinger. 
compRC		con	1		' Set the number to free pin '1' Output to set comparator RC circuit. 
rcvr		con	2		' Set the number to free pin '2' Input from 40kHz receiver/comparator.
pingLen	con	200		' Duration of ping in 2-us units.
echTime VAR word

sonar:
  high ping		' Turn pinger off initially
  high compRC			' Raise C2 to +5 volts. 
  pause 1			' Allow time for C2 to reach +5V. 
  input compRC			' Disconnect pin from C2. 
  pulsout ping,pingLen		' Send a short 40kHz pulse. 
  rctime rcvr,0,echTime		' Wait for echo; save time to echTime.
  if echTime < 150 then hurt
  if echTime > 149 then run
return