ultrasonicdistance.py

import RPi.GPIO as GPIO

import time

import signal

import sys


# use Raspberry Pi board pin numbers

GPIO.setmode(GPIO.BCM)


# set GPIO Pins

pinTrigger = 18

pinEcho = 24


def close(signal, frame):

	print("\nTurning off ultrasonic distance detection...\n")

	GPIO.cleanup() 

	sys.exit(0)


signal.signal(signal.SIGINT, close)


# set GPIO input and output channels

GPIO.setup(pinTrigger, GPIO.OUT)

GPIO.setup(pinEcho, GPIO.IN)


while True:

	# set Trigger to HIGH

	GPIO.output(pinTrigger, True)

	# set Trigger after 0.01ms to LOW

	time.sleep(0.00001)

	GPIO.output(pinTrigger, False)


	startTime = time.time()

	stopTime = time.time()


	# save start time

	while 0 == GPIO.input(pinEcho):

		startTime = time.time()


	# save time of arrival

	while 1 == GPIO.input(pinEcho):

		stopTime = time.time()


	# time difference between start and arrival

	TimeElapsed = stopTime - startTime

	# multiply with the sonic speed (34300 cm/s)

	# and divide by 2, because there and back

	distance = (TimeElapsed * 34300) / 2


	print ("Distance: %.1f cm" % distance)

	time.sleep(1)