ultrasonic.py

import time
import RPi.GPIO as GPIO


GPIO.setmode(GPIO.BCM)


GPIO_TRIGGER = 18
GPIO_ECHO    = 24

print "Ultrasonic Measurement"


GPIO.setup(GPIO_TRIGGER,GPIO.OUT)  
GPIO.setup(GPIO_ECHO,GPIO.IN)      


GPIO.output(GPIO_TRIGGER, False)


time.sleep(0.5)


GPIO.output(GPIO_TRIGGER, True)
time.sleep(0.00001)
GPIO.output(GPIO_TRIGGER, False)
start = time.time()

while GPIO.input(GPIO_ECHO)==0:
  start = time.time()

while GPIO.input(GPIO_ECHO)==1:
  stop = time.time()

elapsed = stop-start


distance = elapsed * 34300


distance = distance / 2

print "Distance : %.1f" % distance


GPIO.cleanup()