The OPC Foundation's OPC UA FX PlugFest (September 7–10, 2026) brought together 28 engineers from 16 companies at Festo's facility in Esslingen, Germany, to test real-world interoperability of OPC UA Field eXchange (OPC UA FX) — the emerging standard for direct, gateway-free communication between industrial controllers. Every tested Controller-to-Controller (C2C) and Controller-to-Device (C2D) communication path passed successfully.
What Is OPC UA FX and Why It Matters
Classic OPC UA runs server-to-client: a SCADA or MES system polls a PLC. OPC UA FX inverts this model and enables PLCs to exchange data directly with each other and with field devices — without routing traffic through an intermediate gateway or DCS. This matters because gateways are bottlenecks: they add latency, create single points of failure, and require bespoke configuration every time a new device joins the network.
OPC UA FX defines two communication patterns:
OPC UA FX Communication Paths
- C2C (Controller-to-Controller) — direct synchronised data exchange between PLCs, enabling peer-to-peer machine coordination across cell boundaries without a supervisory layer.
- C2D (Controller-to-Device) — standardised configuration, parameterisation, and monitoring of field devices (sensors, actuators, drives) directly from the controlling PLC using a common information model.
PlugFest Results: All Paths Passed
At the Esslingen event, participants brought equipment from 16 different vendors — covering a range of PLC families, drive systems, and field device types. The OPC Foundation confirmed that all defined C2C and C2D communication paths completed successfully across every vendor pair. This is a significant milestone: multi-vendor interoperability at the field level has historically been the hardest problem in industrial networking, requiring integrators to maintain stacks of proprietary gateways and protocol bridges.
The results will be demonstrated publicly at SPS Nuremberg (November 24–26, 2026), where OPC Foundation members plan a live interoperability showcase on the show floor.
Spec and Standards Updates Accompanying the PlugFest
The PlugFest coincides with a cluster of standards releases that strengthen the OPC UA FX foundation:
- OPC UA FX Specification V1.00.04 (released July 27, 2026) — maintenance release of Parts 10000-081 and 10000-084. Key changes include improved Asset and FunctionalEntity linking, multi-GDS (Global Discovery Server) address support, enhanced DataSetReader/Writer identification, and configurable communication intervals. These updates reduce integration effort for brownfield deployments where multiple discovery servers coexist.
- APL/SPE Port Specification Revision 3.1 (released September 1, 2026) — standardises physical Single Pair Ethernet (SPE) ports for Ethernet-APL devices, enabling interoperable connections between devices from different manufacturers on the same APL trunk. A conformance test specification for this revision is expected in November 2026.
What This Means for Automation Engineers
Multi-vendor C2C and C2D interoperability means integration projects no longer require custom middleware for each vendor pair. An engineer deploying a mixed-vendor cell — say, a Siemens PLC coordinating with an Allen-Bradley drive and a Pepperl+Fuchs field device — can now rely on a single OPC UA FX stack for the entire communication layer, validated against the same conformance test suite.
Practically, this lowers the barrier to modular machine design (à la OMAC PackML and Module Type Package), where cells from different machine builders need to connect without months of integration work. Combined with Ethernet-APL as the physical layer, OPC UA FX makes the "single-cable, power-and-data" architecture for process instrumentation realistically deployable at scale.
For teams building custom IIoT integration layers — connecting OPC UA FX-enabled shop-floor equipment to MES, ERP, or cloud analytics platforms — YuSMP Group develops industrial software with native OPC UA and REST bridge support.
Source: OPC Foundation — Field Level Communications Corner, September 2026; OPC UA FX Specification V1.00.04 release notes; APL/SPE Port Specification Rev 3.1.