ultrasonic.py

import time  # for delays

import RPi.GPIO as GPIO  # importing GPIO library

GPIO.setmode(GPIO.BCM)  # setting GPIO numbering; BCM sets it according to the Broadcom SOC Channel

TRIG = 23  # pin 16
ECHO = 24  # pin 18

print "Distance measurement in progress..."

GPIO.setup(TRIG, GPIO.OUT)
GPIO.setup(ECHO, GPIO.IN)

GPIO.output(TRIG, False)
print "Waiting for the sensor to settle"
time.sleep(2)  # sleep for 2s

print "Starting"

start_time = time.time()

while time.time() - start_time < 10:
    GPIO.output(TRIG, True)
    time.sleep(0.00001)  # pulse for 10us to trigger the sensor
    GPIO.output(TRIG, False)

    while GPIO.input(ECHO) == 0:
        pass
    pulse_start = time.time()
    while GPIO.input(ECHO) == 1:
        # print GPIO.input(ECHO)
        if time.time() - pulse_start > 0.03:
            pulse_end = None
            break
    else:
        pulse_end = time.time()

    if pulse_end is not None:
        pulse_duration = pulse_end - pulse_start

        # Sound travels at ~343m/s
        # 34300cm/s = 2*distance/time
        # So, distance = time*17150
        distance = pulse_duration * 17150
        distance = round(distance, 2)
        print "Distance: ", distance, " cm"
    else:
        print "Out of Range!!"

GPIO.cleanup()