Extended comments on example for callback_ping_config_and_read

Hello, I also tested the callback-example for Sonar and did some extended comments and also mentioned that the signal_handler doe Ctrl-C will not work very well. If you like, you can replace it in your example or add it as a new one. sorry for not branching/pull request - not so clear to me at the moment (new to git)

#!/usr/bin/env python
"""
Copyright (c) 2013-2015 Alan Yorinks All rights reserved.

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU  General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 General Public License for more details.

You should have received a copy of the GNU  General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
"""
import time
import sys
import signal

from PyMata.pymata import PyMata

# Ping callback function
def cb_ping(data):
    # will always print 11, because first element in data is firmata.SONAR = 0xb = 11
    #print(data[0])
    # will print 12 in this case; it's the pin-number of the attached sonar-device;
    # so here is the place to decide which device has called the callback (if you want to handle multiple devices with one callback)
    # like: if (data[1] == Pin_device_0): ...
    print(data[1])
    print(str(data[2]) + ' centimeters')

# Create a PyMata instance
board = PyMata("COM7", verbose=True)

def signal_handler(sig, frame):
    print('You pressed Ctrl+C!!!!')
    if board is not None:
        board.reset()
        board.close()
    sys.exit(0)

signal.signal(signal.SIGINT, signal_handler)

# Configure pin 12 for SONAR module (see png)
# every 100 ms it will trigger the sonar to meassure the distance and call the callback, if the value has changed compared to previous meassure
# AND the distance is <=100
 board.sonar_config(12, 12, cb_ping, 100, 100)
# if you just do:
#board.sonar_config(12 , 12, cb_ping)
# it will use 50ms as the ping interval and 200 centimeters (which is also the maximum)

# after 30 seconds stop; sleep will sleep the main-thread; so Ctrl-C will not work (at least under Windows) in this time
# so in this example you may also take out the signal_handler if you like; it will work, but directly 
# between the following sleep and the board.close
time.sleep(30)
board.close()

MrYsLab / PyMata

Extended comments on example for callback_ping_config_and_read #18