Ultrahangos távolságmérő Raspberry PI-hez + ajándék extrák

#!/usr/bin/python
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#
# hcsr04.py
# Measure distance using an ultrasonic module
# in a loop.
#
# Author : Matt Hawkins
# Date   : 28/01/2013

# -----------------------
# Import required Python libraries
# -----------------------
import time
import RPi.GPIO as GPIO

# -----------------------
# Define some functions
# -----------------------

def measure():
 # This function measures a distance
 GPIO.output(GPIO_TRIGGER, True)
 time.sleep(0.00001)
 GPIO.output(GPIO_TRIGGER, False)
 start = time.time()

 while GPIO.input(GPIO_ECHO)==0:
   start = time.time()

 while GPIO.input(GPIO_ECHO)==1:
   stop = time.time()

 elapsed = stop-start
 distance = (elapsed * 34300)/2

 return distance

def measure_average():
 # This function takes 3 measurements and
 # returns the average.
 distance1=measure()
 time.sleep(0.1)
 distance2=measure()
 time.sleep(0.1)
 distance3=measure()
 distance = distance1 + distance2 + distance3
 distance = distance / 3
 return distance

# -----------------------
# Main Script
# -----------------------

# Use BCM GPIO references
# instead of physical pin numbers
GPIO.setmode(GPIO.BCM)

# Define GPIO to use on Pi
GPIO_TRIGGER = 23
GPIO_ECHO    = 24

print "Ultrasonic Measurement"

# Set pins as output and input
GPIO.setup(GPIO_TRIGGER,GPIO.OUT)  # Trigger
GPIO.setup(GPIO_ECHO,GPIO.IN)      # Echo

# Set trigger to False (Low)
GPIO.output(GPIO_TRIGGER, False)

# Wrap main content in a try block so we can
# catch the user pressing CTRL-C and run the
# GPIO cleanup function. This will also prevent
# the user seeing lots of unnecessary error
# messages.
try:

 while True:

   distance = measure_average()
   print "Distance : %.1f" % distance
   time.sleep(1)

except KeyboardInterrupt:
 # User pressed CTRL-C
 # Reset GPIO settings
 GPIO.cleanup()