Modbus to OPC UA
Rather than pushing data out, the Gateway can serve it. It runs an OPC UA server, and the tags it polls over Modbus appear as read-only variables that any OPC UA client can browse, read and subscribe to.
Typical use case
A SCADA system, a historian or an MES speaks OPC UA and the field device speaks Modbus. This gives the Modbus device an OPC UA face without touching the device or the SCADA driver licence.
Configuration approach
Define the tags as usual
The same Modbus device and tag definitions; no separate configuration for the OPC UA side.
Address space
Tags appear under a folder per device, with node IDs of the form ns=2;s=Device.Tag.
Value, type, unit, quality
Each variable carries its data type, its engineering unit as an EngineeringUnits property, a status code derived from tag quality, and the source timestamp of the read.
Endpoint security
An unencrypted endpoint, Basic256Sha256 with Sign & Encrypt, or both. The gateway generates and keeps its own application certificate, or uses one you supply.
Questions engineers ask
Can a client write to a tag?
No. Every variable is read-only and a write is refused. The runtime has no write path towards the plant at all.
Does it support subscriptions?
Yes. Clients subscribe and receive data changes as the runtime polls.
Build a Modbus to OPC UA gateway
Create a project, define the device and its tags in the Edge Logic Editor, and download a runtime to test at the plant.