# coding=gbk
import RPi.GPIO as GPIO
import time

# GPIO Mode (BOARD / BCM)
GPIO.setmode(GPIO.BCM)

# set GPIO Pins and speed
GPIO_TRIGGER = 23
GPIO_ECHO = 24
GPIO_SPEED = 340

# set GPIO direction (IN / OUT)
GPIO.setup(GPIO_TRIGGER, GPIO.OUT)
GPIO.setup(GPIO_ECHO, GPIO.IN)

def distance():
    # set Trigger to HIGH
    GPIO.output(GPIO_TRIGGER, True)

    # set Trigger after 0.01ms to LOW
    time.sleep(0.00001)
    GPIO.output(GPIO_TRIGGER, False)

    StartTime = time.time()
    StopTime = time.time()

    # save StartTime
    while GPIO.input(GPIO_ECHO) == GPIO.LOW:
        StartTime = time.time()

    # save time of arrival
    while GPIO.input(GPIO_ECHO) == GPIO.HIGH:
        StopTime = time.time()

    # time difference between start and arrival
    TimeElapsed = StopTime - StartTime
    # multiply with the sonic speed (34000 cm/s)
    # and divide by 2, because there and back
    distance = (TimeElapsed * GPIO_SPEED * 100) / 2
    return distance

if __name__ == ‘__main__‘:
    try:
        while True:
            dist = distance()
            print(" Measured Distance = %.1f cm" % dist)
            time.sleep(1)
    # Reset by pressing CTRL + C
    except KeyboardInterrupt:
        print(" Measurement stopped by User")
        GPIO.cleanup()