import RPi.GPIO as GPIO
import time

TRIG = 23
ECHO = 24


def init_us():
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(TRIG, GPIO.OUT)
    GPIO.setup(ECHO, GPIO.IN)
    GPIO.output(TRIG, False)
    print "Waiting For Sensor To Settle"
    time.sleep(2)


def measure_distance():
    global pulse_end, pulse_start
    GPIO.output(TRIG, True)
    time.sleep(0.00001)
    GPIO.output(TRIG, False)

    while GPIO.input(ECHO) == 0:
        pulse_start = time.time()

    while GPIO.input(ECHO) == 1:
        pulse_end = time.time()

    pulse_duration = pulse_end - pulse_start

    distance = pulse_duration * 17150

    distance = round(distance, 2)

    return num2words(distance)


def cleanup_us():
    GPIO.cleanup()