#!/usr/bin/python

import pigpio
import time

_TRIG=5             # hc-sr04 tigger pin
_ECHO=6             # hc-rc04 echo pin
                    # this one must be brought down to 3.3V
		    # from the hc-sr04 5V level through a level converter
pi = pigpio.pi()    # access the local Pi's gpio
pi.set_mode (_TRIG, pigpio.OUTPUT)
pi.set_mode (_ECHO, pigpio.INPUT)
pi.write(_ECHO, pigpio.LOW)

print "hardware revision " + str(pi.get_hardware_revision())

while True:
    
    print "triggering"
    pi.write(_TRIG,pigpio.HIGH)
    time.sleep(0.00001)       # wait 10 us
    pi.write(_TRIG,pigpio.LOW)

    while pi.read(_ECHO) == pigpio-LOW:
        start = time.time()
    while pi.read(_ECHO) == pigpio.HIGH:
        stop = time.time()
    duration = stop - start
    distance = duration * 17150
    
    print "distance" + str(distance) + "cm"
    time.sleep(1)