pyFirmata2 0.9.1

A realtime Python interface for the Firmata procotol

PyFirmata2 is an API which allows you to sample directly analogue and digital data from the ports of your Arduino without writing any C code. Just upload the default firmata sketch into your Arduino and you are all set.

The Python API is fully compatible with Firmata 2.1, and has some functionality of version 2.2. It runs on Python 2.7, 3.3, 3.4, 3.5 and 3.6

pyFirmata2 is an updated version of pyFirmata where you can measure at a given sampling rate which then allows digital filtering, for example with an realtime IIR filter.

Installation

First upload the standard firmata sketch into your Arduino with File -> Examples -> Firmata -> Standard Firmata.

Then install pyFirmata2. The preferred way to install is with pip:

pip3 install pyfirmata2

You can also install from source with python setup.py install. You will need to have setuptools installed:

git clone https://github.com/berndporr/pyFirmata2
cd pyFirmata2
python3 setup.py install

Usage

Basic usage:

>>> from pyfirmata import Arduino
>>> board = Arduino('/dev/tty.usbserial-A6008rIF')
>>> board.digital[13].write(1)

To switch on contious data acquisition from the inputs of the board run:

>>> board.samplingOn()

To enable sampling at the exact sampling interval (min 10ms) use the optional argument of samplingOn:

>>> board.samplingOn(samplinginterval in ms)

The individual analoge pins are enabled / read by:

>>> board.analog[0].enable_reporting()
>>> board.analog[0].read()
0.661440304938

In order to process the data at the given sampling interval register a callback handler:

>>> board.analog[0].register_callback(myCallback)

where myCallback(data) is then called every time when data has been received and is timed by the arduino itself. This is very precise up to 100Hz sampling rate (10ms sampling interval).

If you use a pin more often, it can be worth using the get_pin method of the board. It let’s you specify what pin you need by a string, composed of ‘a’ or ‘d’ (depending on wether you need an analog or digital pin), the pin number, and the mode (‘i’ for input, ‘o’ for output, ‘p’ for pwm). All seperated by :. Eg. a:0:i for analog 0 as input or d:3:p for digital pin 3 as pwm.:

>>> analog_0 = board.get_pin('a:0:i')
>>> analog_0.read()
0.661440304938
>>> pin3 = board.get_pin('d:3:p')
>>> pin3.write(0.6)

Board layout

If you want to use a board with a different layout than the standard Arduino or the Arduino Mega (for which there exist the shortcut classes pyfirmata.Arduino and pyfirmata.ArduinoMega), instantiate the Board class with a dictionary as the layout argument. This is the layout dict for the Mega for example:

>>> mega = {
...         'digital' : tuple(x for x in range(54)),
...         'analog' : tuple(x for x in range(16)),
...         'pwm' : tuple(x for x in range(2,14)),
...         'use_ports' : True,
...         'disabled' : (0, 1, 14, 15) # Rx, Tx, Crystal
...         }

Credits

The original pyFirmata has been written by Tino de Bruijn. The realtime sampling / callback has been added by Bernd Porr.