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2022-11-28 - 13:12

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OSADL Articles:

2022-01-13 12:00

Phase #3 of OSADL project on OPC UA PubSub over TSN successfully completed

Another important milestone on the way to interoperable Open Source real-time Ethernet has been reached


2021-02-09 12:00

Open Source OPC UA PubSub over TSN project phase #3 launched

Letter of Intent with call for participation is now available


2016-11-12 12:00

Raspberry Pi and real-time Linux

Let's have a look at the OSADL QA Farm data



The OSADL OPC UA PubSub over TSN Project

Project phase #1 - Project phase #2 - Project phase #3 - Project phase #4 - Presentations

Rationale

State of the art

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.

Next generation OPC UA

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.

Project phases

  • Phase #4 (Letter of intent launched)
    • Load and store information data model at run time through configuration file (not statically compiled in firmware)
    • Implement “reverse connect feature” as described in "OPC 10000-7 - Part 7: Profiles", chapters 6.6.5 Reverse Connect Server Facet and 6.6.75 Reverse Connect Client Facet
    • Complement the ongoing project to update the OPC client/server release to version 1.05 without overlapping with the parts already commissioned
    • Implement support of PubSub state machine according to OPC10000-14, chapter 6.2.1
    • Companion specification selection in the build system for fast integration
    • Automatic size-reduction of the information model by white-listing and dependency resolution
    • Further CPU and memory optimizations for resource constrained devices (identify, document and implement optimizations for memory and CPU footprint)
  • Phase #3 (completed)
    • Security support for the UADP protocol
    • Providing certification prerequisites according to the “Full Embedded Profile” by OPC Foundation
  • Phase #2 (completed)
    • Successful certification of an example server according to the “Micro Embedded Device Server” profile by OPC Foundation
    • PubSub implementation as stand-alone server
  • Phase #1 (completed)
    • 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

Presentations

In-depth presentations along with a video clip are available here.