import RPi.GPIO as GPIO
import time
import sys

TRIGER = 23
ECHO = 24

GPIO.setmode(GPIO.BCM)
GPIO.setup(TRIGER, GPIO.OUT)
GPIO.setup(ECHO, GPIO.IN)

def read_distance():
    GPIO.output(TRIGER, GPIO.HIGH)
    time.sleep(0.00001)                     #wait time(10μS)
    GPIO.output(TRIGER, GPIO.LOW)

    while GPIO.input(ECHO) == GPIO.LOW:
        sig_off = time.time()
    while GPIO.input(ECHO) == GPIO.HIGH:
        sig_on = time.time()

    duration = (sig_on - sig_off)
    distance = duration * 34000 / 2
    return distance

try:
    while True:
        cm = read_distance()
        if cm >= 2.0 and cm <= 400.0:
            print('distance =', '{:.2f}'.format(cm))
        time.sleep(1)

except KeyboardInterrupt:
    GPIO.cleanup()