Due to its simple structure and many years of history, the Modbus transmission protocol is widespread on many devices and systems.

As a modern, web-based HMI/SCADA system, WebIQ relies on the current OPC-UA communication standard, which today is supported by most PLC controller manufacturers. OPC-UA has the advantage that this is a manufacturer-independent standard and the HMI can be used independently of a specific controller manufacturer.

To be able to integrate existing Modbus RTU or TCP infrastructure into such a solution, Smart HMI offers a Modbus-to-OPC-UA gateway, via which the existing Modbus devices can be integrated via an OPC-UA server.

Smart HMI’s Modbus-to-OPC-UA gateway is designed to integrate with the WebIQ system via OPC-UA. The module can be configured via a configuration file config.json and runs on Windows 10 or 11 and on their embedded variants. The gateway can either be started as a console program with error and warning messages output via the console, or alternatively as a tool in the background. In both cases, messages can be logged to a log file.

The Modbus-to-OPC-UA gateway package from Smart-HMI is an open-source program and can be downloaded from Smart HMI via the MyWebIQ customer area . Prior signup on the Smart-HMI website is required for access.

The package is delivered including the source files and can be used free of charge under the open-source MIT license. The programming was done in JavaScript with Node.js, so that it can also run on Linux or on other operating systems. On Windows it is possible to start an executable file, modbus-opcua.exe, in the dist subdirectory by double-clicking on the file or by executing the batch file start.bat directly.

The Modbus part runs as a master and supports the Modbus functions 1-6 and 15, 16. Any number of Modbus devices can be queried, whereby the Modbus registers are mirrored directly into the name space of the OPC-UA server.

Registers of the Modbus device are mirrored in the OPC-UA namespace

The Modbus-to-OPC-UA gateway supports the simple integration of Modbus devices into the HMI-/SCADA system WebIQ.