#!/usr/bin/python
# -*- coding:utf-8 -*-

import RPi.GPIO as GPIO
import time

TRIG = 11
ECHO = 12


def setup():
    GPIO.setmode(GPIO.BOARD)
    GPIO.setup(TRIG, GPIO.OUT)
    GPIO.setup(ECHO, GPIO.IN)


def distance():
    GPIO.output(TRIG, 0)
    time.sleep(0.000002)

    GPIO.output(TRIG, 1)
    time.sleep(0.00001)
    GPIO.output(TRIG, 0)

    while GPIO.input(ECHO) == 0:
        a = 0
    time1 = time.time()
    while GPIO.input(ECHO) == 1:
        a = 1
    time2 = time.time()

    during = time2 - time1
    return during * 340 / 2 * 100


def loop():
    while True:
        dis = distance()
        print dis, 'cm'
        print ''
        time.sleep(0.3)


def destroy():
    GPIO.cleanup()


if __name__ == "__main__":
    setup()
    try:
        loop()
    except KeyboardInterrupt:
        destroy()