#!/usr/bin/python
import time
import RPi.GPIO as GPIO

GPIO_BEGIN_PIN = 4
GPIO_END_PIN = 17

DISTANCE = 10.0 # (in cm) Anpassen, falls notwendig
TIMEOUT = 5 # sek

GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)

if __name__ == '__main__':
	GPIO.setup(GPIO_BEGIN_PIN, GPIO.IN)
	GPIO.setup(GPIO_END_PIN, GPIO.IN)
	start_time, end_time = 0, 0
	
	while GPIO.input(GPIO_BEGIN_PIN) == GPIO.LOW:
		time.sleep(0.001)
		start_time = time.time()
	end_time = 0

	while GPIO.input(GPIO_END_PIN) == GPIO.LOW and time.time()-start_time < TIMEOUT:
		time.sleep(0.001)
	else: 
		if time.time()-start_time >= TIMEOUT:
			print "Timeout"
			exit()
		else:
			end_time = time.time()

			speed = DISTANCE / (end_time - start_time)
			print "Geschwindigkeit: %.2f cm/s" % speed