MERLIN: OPC UA IOC similar to MAPS for Vacuum tank control

[esmith1729]

Feature Description

Discussed 10/07/2025 1:00:36

As a user, I would like to control the MERLIN Pressure Tank in IBEX via an OPCUA IOC and OPI so that I can keep up to date with the vacuum system upgrade that will occur on MERLIN.

Explanation

_{Aim to describe the ticket as if you're explaining it to someone who is new to this technology/subject area.}

OPCUA servers are being rolled out for various instruments at ISIS. They are an asynchronous way to read and write values from a PLC to various devices connected to the PLC. This IOC will be incredibly similar to the MAPS OPC Server IOC #8586, will likely be a .db file or two with the PV values, and a .cmd file to go in the config area of MERLIN. Tests should already be covered by #8586 unless there is some functionality that arises from this work that did not exist from that ticket.

Additional Information

_{What else do I need to know before starting?}

• ioc/master/OPCUA/db create a new .db file here for MERLIN's OPC server.
• You will likely need to contact either Aamir Khokhar or Instrumentation and Control Systems group (Tim Carter) for details of what PV values are needed on MERLIN for this ticket
• MAPS: Provide support to read pressure values from vacuum PLC #8586

_{See our Git Workflow.}

Acceptance Criteria

_{What is the acceptance criteria of this ticket? What should the reviewer expect to be complete?}

• An IOC can read (and write if needed) values to the MERLIN OPC Server
• An OPI is adapted or created specific to MERLIN for this IOC, and is error-free.
• A folder is added to opcua\ folder in the ISISExperimentControls network share that has
  • a .cmd file (similar to that for MAPS) with MERLIN specific DbLoadRecords calls
  • a copy of client_private_key to encrypt password for connection to the server
  • a .txt file with username and password

How to Review

_{Before making a PR...}

• Install the opcua\MERLIN_OPC folder from the ExpCtrls network share (non-public) to you <NDW####\configurations\ area and rename it opcua (to be picked up by the OPCUA IOC.
• make the OPCUA IOC in ioc\master
• Start IBEX server and the GUI, and add a device screen and ensure that the OPI is reading properly (might need to contact Aamir or ICS team to check that OPC server is not currently in use).

_{To the reviewer: Make sure to update submodules!}

[Tom-Willemsen]

@davidkeymer please chase and figure out if this is needed imminently

[davidkeymer]

Latest update from TC and co. is that MERLIN and GEM will have their PLCs upgraded either in the Easter '26 shutdown or in the following cancelled cycle.

Will move this ticket to next PI.