pyhoff

Pyhoff

The pyhoff package allows you to read and write the most common Beckhoff and WAGO bus terminals ("Busklemmen") using the Ethernet bus coupler ("Busskoppler") BK9000, BK9050, BK9100, or WAGO 750_352 over Ethernet TCP/IP based on ModBus TCP.

Key Features

• Supports a wide range of Beckhoff and WAGO analog and digital bus terminals.
• Very lightweight: no dependencies; compact code base
• Easy to extend
• Using standardized ModBus TCP.
• Provides high-level abstractions for reading and writing data from/to IO-terminals with minimal code

Usage Scenarios

• Industrial test setups.
• Research automation setups.
• Data acquisition and monitoring.

Installation

The package has no additional decencies. It can be installed with pip:

pip install pyhoff

Usage

It is easy to use as the following example code shows:

from pyhoff.devices import *

# connect to the BK9050 by tcp/ip on default port 502
bk = BK9050("172.16.17.1")

# add all bus terminals connected to the bus coupler
# in the order of the physical arrangement
bk.add_bus_terminals(KL2404, KL2424, KL9100, KL1104, KL3202,
                     KL3202, KL4002, KL9188, KL3054, KL3214,
                     KL4004, KL9010)

# Set 1. output of the first KL2404-type bus terminal to hi
bk.select(KL2404, 0).write_coil(1, True)

# read temperature from the 2. channel of the 2. KL3202-type
# bus terminal
t = bk.select(KL3202, 1).read_temperature(2)
print(f"t = {t:.1f} °C")

# Set 1. output of the 1. KL4002-type bus terminal to 4.2 V
bk.select(KL4002, 0).set_voltage(1, 4.2)

Adding new terminals

The package comes with automatic generated code stubs for nearly all terminals. These stubs are not tested with hardware but for most digital IO terminals the code should be fully functional. Such a stub looks like this:

# From ./src/pyhoff/devices.py:
class KL2442(DigitalOutputTerminal):
    """
    KL2442: 2-channel digital output, 24 V DC, 2 x 4 A/1 x 8 A
    (Automatic generated stub)
    """
    parameters = {'output_bit_width': 2, 'input_bit_width': 0}

For analog IO terminals the stubs are functional as well, but they provide only a generic read_channel_word and read_normalized function (for inputs) without scaling the values to voltages, currents or temperatures. For better usability they might be extended with functions. Based on the stub the extension could look like this:

from pyhoff.devices import KL3054 as KL3054_stub

class KL3054(KL3054_stub):
    def read_current(self, channel: int) -> float:
        return self.read_normalized(channel) * 16.0 + 4.0

Or for contributing to the pyhoff package, the existing stub code can be updated like this:

# From ./src/pyhoff/devices.py:
class KL3054(AnalogInputTerminal):
    """
    KL3054: 4x analog input 4...20 mA 12 Bit single-ended
    """
    # Input: 4 x 16 Bit Daten (optional 4x 8 Bit Control/Status)
    parameters = {'input_word_width': 4}

    def read_current(self, channel: int) -> float:
        """
        Read the current value from a specific channel.

        Args:
            channel: The channel number to read from.

        Returns:
            The current value in mA.
        """
        return self.read_normalized(channel) * 16.0 + 4.0

Contributing

Other analog and digital IO terminals are easy to complement. Contributions are welcome! Please open an issue or submit a pull request on GitHub.

Developer Guide

To get started with developing the pyhoff package, follow these steps:

• First, clone the repository to your local machine using Git:

  git clone https://github.com/Nonannet/pyhoff.git
  cd pyhoff
  

• It is recommended to use a virtual environment:

  python -m venv .venv
  source .venv/bin/activate  # On Windows/Powershell use `.\venv\Scripts\Activate.ps1`
  

• Install pyhoff from source plus the development dependencies:

  pip install -e .[dev]
  

• Ensure that everything is set up correctly by running the tests:

  pytest
  

License

This project is licensed under the MIT License - see the LICENSE file for details.