pymata-express

Please note that the pymata-express feature set is now frozen and the project has been placed in maintenance mode.

Please consider using Telemetrix instead.

A high performance, Python asyncio client for the Arduino Firmata Protocol.

Pymata-Express is a Firmata client that, like its conventional Python sibling, pymata4, allows you to control an Arduino using the high-performance FirmataExpress sketch. It uses a conventional Python API for those that do not need or wish to use the asyncio programming paradigm of pymata-express.

It supports both an enhanced version of StandardaFirmata 2.5.8, called FirmataExpress, as well as StandardFirmata and StandardFimataWiFi.

• FirmataExpress adds support for:
  • HC-SR04 Ultrasonic Distance Sensors using a single pin.
  • DHT Humidity/Temperature Sensors.
  • Stepper Motors.
  • Piezo Tone Generation.
  • Baud rate of 115200

Special Note For FirmataExpress Users:

pymata-express now verifies the version of FirmataExpress in use. You may need to upgrade to the latest version of FirmataExpress using the Arduino IDE Library management tool.

Special Note For Users Upgrading To Version 1.11

The callback data format has changed to be consistent with pymata4.

Callback	Prior To Version 1.11	Version 1.11 And Above
analog input	[pin, current reported value, pin_mode, timestamp]	[pin_mode = 2, pin, current reported value, pin_mode, timestamp]
digital input	[pin, current reported value, pin_mode, timestamp]	[pin_mode = 0, pin, current reported value, pin_mode, timestamp]
hc-sr04	[pin, distance]	[pin_mode=12, trigger pin number, distance, timestamp]
i2c	[Device address, data bytes]	[pin_mode=6, i2c device address, data bytes, timestamp]

Major features

• Fully documented intuitive API

• Python 3.7+ compatible.

• Set the pin mode and go!

• Data change events may be associated with a callback function, or each pin can be polled for its last event change.

  • Each data change event is time-stamped and logged.

• User's Guide, Including Examples.

• Implements 100% of the StandardFirmata Protocol (StandardFirmata 2.5.8).

• Advanced auto-detection of Arduino devices (when using FirmataExpress).

Here is an example that monitors data changes on a digital input pin.

import asyncio
import time
import sys
from pymata_express import pymata_express

"""
Setup a pin for digital input and monitor its changes
using a callback.
"""

# Setup a pin for analog input and monitor its changes
DIGITAL_PIN = 12  # arduino pin number
IDLE_TIME = .001  # number of seconds for idle loop to sleep

# Callback data indices
# Callback data indices
CB_PIN_MODE = 0
CB_PIN = 1
CB_VALUE = 2
CB_TIME = 3


async def the_callback(data):
    """
    A callback function to report data changes.
    This will print the pin number, its reported value and
    the date and time when the change occurred

    :param data: [pin, current reported value, pin_mode, timestamp]
    """
    date = time.strftime('%Y-%m-%d %H:%M:%S', time.localtime(data[CB_TIME]))
    print(f'Pin: {data[CB_PIN]} Value: {data[CB_VALUE]} Time Stamp: {date}')


async def digital_in(my_board, pin):
    """
     This function establishes the pin as a
     digital input. Any changes on this pin will
     be reported through the call back function.

     :param my_board: a pymata_express instance
     :param pin: Arduino pin number
     """

    # set the pin mode
    await my_board.set_pin_mode_digital_input(pin, callback=the_callback)

    while True:
        try:
            await asyncio.sleep(IDLE_TIME)
        except KeyboardInterrupt:
            await board.shutdown()
            sys.exit(0)

# get the event loop
loop = asyncio.get_event_loop()

# instantiate pymata_express
board = pymata_express.PymataExpress()

try:
    # start the main function
    loop.run_until_complete(digital_in(board, 12))
except (KeyboardInterrupt, RuntimeError) as e:
    loop.run_until_complete(board.shutdown())
    sys.exit(0)

Sample console output as input change events occur:

Pin: 12 Value: 0 Time Stamp: 2020-03-10 13:26:22
Pin: 12 Value: 1 Time Stamp: 2020-03-10 13:26:27

This project was developed with Pycharm