Raspberry PI controlling an Arduino via the pyfirmata protocol


    The Raspberry PI is good for a lot of things from computer clusters to home automation but its missing a few things such as a real time clock, terminal/barrel power connector, or  Analog pins.  The Arduino has analog pins that can be read by the USB virtual serial port from the Raspberry PI.

    2013-02-10 21.31.34

    In MagPI issue 7, has a great article on using the firmata protocol to communicate between   Arduino and the Raspberry PI.


    Install and setup 

    1. Enable SSH on the Raspberry PI
    2. Install Adafruit Learning System Raspberry Pi WebIDE
    3. Get the required packages:
      sudo apt-get install python-serial mercurial
    4. Install pyFirmata
      sudo apt-get install python-serial mercurial
      hg clone https://bitbucket.org/tino/pyfirmata
      cd pyfirmata
      sudo python setup.py install
      cd .. ; sudo rm -r pyfirmata

    Source code 

    Read analog pin 1

    import pyfirmata
    # Create a new board, specifying serial port
    board = pyfirmata.Arduino('/dev/ttyACM0')
    # start an iterator thread so that serial buffer doesn't overflow
    it = pyfirmata.util.Iterator(board)
    # set up pins
    pin0=board.get_pin('a:0:i')             # A0 Input      (LM35)
    pin3=board.get_pin('d:3:p')             # D3 PWM Output (LED)
    # IMPORTANT! discard first reads until A0 gets something valid
    while pin0.read() is None:
    while True : 
      print "PWM: " + str( pin0.read() ) 
    	board.pass_time(1)                  # pause 1 second