open62541: Open-source OPC UA stack suitable for embedded systems

Open62541 is an open implementation of OPC UA, the world language of machine-to-machine communication, programmed entirely in C. This means that the software, which was largely developed at the Fraunhofer Institute of Optronics, System Technologies and Image Exploitation IOSB in Karlsruhe, is extremely resource-efficient and runs on all types of hardware, from small embedded systems to large production plants. In 2019 open62541 has received the decisive seal of approval: The OPC Foundation announced the official certifiability of OPC UA servers based on version 1.0 of the open OPC UA stack.

OPC UA, the Open Platform Communications Unified Architecture, is the open standard with which any type of machine can communicate with each other in an industrial context. Individual sensors up to complete production lines, power plants or oil platforms are mapped in a server-side information model and controlled by a client software. This enables data exchange, intelligent data evaluation and process control. As a manufacturer-independent standard, OPC UA is considered a basic technology for industry 4.0 applications. OPC UA is published, further developed and managed by the OPC Foundation based in the USA.

open62541 is an open source implementation of the OPC UA communication protocol, which is being driven by the Fraunhofer IOSB together with the Indian system integrator Kalycito and the Open Source Automation Development Lab (OSADL). The software library is written in the C programming language, more precisely in the common subset of C99 and C++98.

Suitable for any hardware

This means that the software can be used with all common compilers and is so resource-saving that it runs on any conceivable hardware. It enables both dedicated OPC UA servers to be set up and OPC UA-based communication to be integrated into existing applications," explains Dr. Julius Pfrommer, group leader for Cyberphysical Distributed Systems in the Information Management and Control Technology (ILT) department at the Fraunhofer IOSB and leading software architect behind open62541. Bhagath Singh Karunakaran, founder and CEO of Kalycito Infotech Private Ltd. adds: "We firmly believe that the open source development model is ideally suited for basic technologies such as operating systems and communication and will lead to better results faster. It avoids unnecessary parallel developments and ensures a rapid spread of innovative software solutions".

The certification was carried out using a representative example server based on open62541. The certified scope includes the 'Micro Embedded Device Server' profile, which additionally supports subscriptions, method calls and encryption. Furthermore, open62541 version 1.0 also supports communication according to the OPC UA Publisher/Subscriber model, so that asynchronous communication with several participants is also possible. For OPC UA Pub/Sub there is currently no official certification offered by the OPC Foundation.

The software is licensed under the Mozilla Public License v2.0 (MPL-2.0). Thus the open62541 library may be linked and distributed with proprietary software. Only further developments of the open62541-library itself have to be licensed under MPL-2.0 when redistributed.

Consistent real-time Ethernet solution planned

Dr. Carsten Emde, Managing Director of the Open Source Automation Development Lab (OSADL) eG, thanks the participating companies for their financial support, without which the project would not have come about.

At the same time, he points out that with this certification, the project is by no means complete, but that the development continues - among other things, towards an integrated and freely available solution for real-time Ethernet via connection to TSN. For this purpose, he welcomes further interested companies: "The more companies participate in the project, the more powerful and versatile components can be developed and contributed. The project is designed in such a way that companies can join at any time even after the project has started, and we would therefore like to take this opportunity to motivate other interested companies to participate".

Project partners

  • Balluff GmbH
  • Heidelberger Druckmaschinen AG
  • Intel Corporation
  • iss innovative software services GmbH
  • Linutronix GmbH
  • Nestfield Co., Ltd
  • Pepperl+Fuchs AG
  • Pilz GmbH & Co. KG
  • Sick AG
  • Siemens AG
  • TQ-Systems GmbH
  • WIKA Mobile Control GmbH & Co. KG

The current developments were made possible by an OSADL community project in which the companies mentioned above are involved.


Department KIS of Fraunhofer IOSB

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