The Ethernet standard and the future evolution of this base communication layer represents today an important standard of interoperable network communication - in fact from sensor via control system up to the server. According to common understanding, this will remain so without doubt in the near and even less near future. To the contrary, there are many doubts that the upper communication layers will remain as they are now, since the desired deterministic and interoperable connectivity of the future requires that only a single protocol be used - instead of the more than 40 different ones none of which has reached more than 50 percent market share. In addition, communication methods are needed that require much less resources than today which is an important prerequisite to serve the expected large number of future nodes.
In order to obtain the mentioned interoperable connectivity, it was proposed some time ago to equip the already existing OPC UA protocol with additional features needed by industry and establish it as a unified communication protocol of the future. OPC UA runs even on systems that provide only a minimum of resources with respect to network bandwidth and computing power. Deterministic communication via this protocol shall be obtained using Time Sensitive Networking (TSN) that currently undergoes standardization. Two important protocol additions needed by industry that also are about to be standardized are Publish ("Pub") and Subscribe ("Sub"). While the former is needed to simultaneously send messages to a number of receivers, the latter allows a program component to register for a particular event such as sensor data exceeding or falling below permissible limits to avoid polling.
In addition to the standardization of the protocols, to gain general acceptance of this technology it also is necessary to provide a freely accessible software implementation that can be used in an unrestricted way. Since this currently is not not the case, the Open Source Automation Development Lab (OSADL) in collaboration with Indian system integrator Kalycito Infotech has launched a related Open Source software project that is funded by Kalycito and an OSADL project group. The already developed and further to be enhanced software is based on the OPC UA implementation that was created in the open62541 project (ht tps://open62541.org/). The Fraunhofer Institute of Optronics, System Technologies and Image Processing (Fraunhofer IOSB) has taken over the activity of programming the OPC UA enhancements; this was a logical decision, since Fraunhofer IOSB already played an important role in the development of the original open62541 project.
The currently available results of the named project will be presented at the OSADL booth of Embedded World 2018 (hall 4, booth 168) in a demonstrator with several TSN nodes and concurrent real-time and non-real-time communication. The demonstrator contains a variety of TSN hardware and software implementations of various vendors that communicate to each other using a unified OPC UA implementation and provides the following features for the first time under an Open Source license that can be used in proprietary products:
- Brokerless OPC UA Pub/Sub via IP multicast and the binary message encoding format according to draft of part 14 of the OPC UA specification
- Integration of the publisher in a regular OPC UA server with additional real-time interrupting
- Implementation of the subscribers as standalone software
Intel Atom/I210 by TQ-Systems
FPGA-TSN by Analog Devices
FPGA-TSN Cyclone V SoC by Intel/Altera
FPGA-TSN Zync SoC by Xilinx
Software development and project management:
Open Source Automation Development Lab (OSADL)
Partial funding and other contributions through the following participants of the OSADL project: