PLC Modbus TCP Block

[reedajohns]

Description

Creates a new Modbus TCP communication block. The block uses the pymodbus library to read from and write to PLC registers over Modbus TCP. It supports three modes of operation:

• read: Reads specified registers from a PLC.
• write: Writes specified values to PLC registers.
• read_and_write: Performs both reading and writing operations in one execution.

Adding Modbus TCP support allows workflows to interact with a broader range of PLCs and industrial devices that use the Modbus protocol.

Type of change

• [ x] New feature (non-breaking change which adds functionality)

How has this change been tested, please provide a testcase or example of how you tested the change?

Tested locally on a PLC with Modbus TCP enabled. Ensured that we can robustly:

• Connect to a PLC via Modbus TCP
• Read Registers
• Write Registers

Created Unit test to simulate Modbus client responses. Tests cover successful read/write operations as well as failure scenarios (connection, read, and write failures).

Any specific deployment considerations

• The environment must allow network access to the target PLC's IP and Modbus port.
• Proper configuration of register addresses and values must be provided in workflows.

Docs

NA

[grzegorz-roboflow]

@reedajohns it seems tests fail because pymodbus cannot be installed:

ERROR: No matching distribution found for pymodbus==3.8.3