PyMata

PyMata is a high performance, multi-threaded, non-blocking Python client for the Firmata Protocol that supports the complete StandardFirmata protocol.

A new version for Python 3.4.3, pymata_aio, can be found here.

##Major features

• Implements the entire Firmata 2.4.1 protocol.
• Python 2.7+ and Python 3.4+ compatibility through a shared code set. (If you are running Python 3.4 on Linux, please see note below).
• Easy to use and intuitive API. You can view the PyMata API Documentation here or view in the Documentation/html directory.
• Custom support for stepper motors, Sonar Ping Devices (HC-SRO4), Piezo devices and Rotary Encoders.
• Wiring diagrams are provided for all examples in the examples directory.
• Digial and Analog Transient Signal Monitoring Via Data Latches:
  • They provide "one-shot" notification when either a digital or analog pin meets a user defined threshold.
  • Analog latches compare each data change to a user specified value.
    • Comparison operators are <, >, <= and >=
  • Digital latches compare a data change to either a high or low, specified by the user.
  • Latches can easily be re-armed to detect the next transient data change.
  • Latches can be either manually read or a callback can be associated with a latch for immediate notification.
• Optional callbacks provide asynchronous notification of data updates.

Callbacks

Check out the example code on the wiki.

• Digital input pins.
• Analog input pins.
• Encoder changes.
• I2C read data changes.
• SONAR (HC-SR04) distance changes.
• Analog latch condition achieved.
• Digital latch condition achieved.
• Callbacks return data reports in a single list format.
• Polling methods and callbacks are available simultaneously and can be used in a mixed polled/callback environment.
• Callbacks return data in a single list.

The callback data return values

Callback Type	List Element 0	List Element 1	List Element 2	List Element 3
Analog	ANALOG MODE	Pin Number	Data Value	Not Applicable
Digital	DIGITAL MODE	Pin Number	Data Value	Not Applicable
I2C	I2C MODE	I2C Device Address	Data Value	Not Applicable
Sonar	Trigger Pin	Distance in Centimeters	Not Applicable	Not Applicatble
Encoder	Encoder MODE	Pin Number	Data Value	Not Applicable
Latched Analog	LATCHED ANALOG MODE	Pin Number	Data Value	Time Stamp
Latched Digital	LATCHED DIGITAL MODE	Pin Number	Data Value	Time Stamp

Control-C Signal Handler

Below is a sample Control-C signal handler that can be added to a PyMata Application. It suppresses exceptions being reported as a result of the user entering a Control-C to abort the application.

import sys
import signal
# followed by another imports your application requires

# create a PyMata instance
# set the COM port string specifically for your platform
board = PyMata("/dev/ttyACM0")

# signal handler function called when Control-C occurs
def signal_handler(signal, frame):
    print('You pressed Ctrl+C!!!!')
    if board != None:
        board.reset()
    sys.exit(0)

# listen for SIGINT
signal.signal(signal.SIGINT, signal_handler)

# Your Application Continues Below This Point

Misc

• Want to extend PyMata? See Our Instructables Article explaining how stepper motor support was added. Use it as a guide to customize PyMata for your own needs.
• Check Out Mr. Y's Blog Here for all the latest news!

Special Note For Linux Users Wishing to Use Python 3.4

pymata_aio is now available and for Python 3.4.3.

Check out the pymata_aio wiki!