EUROTHERM: MODBUS Control

[KathrynBaker]

As someone supporting Eurotherms at ISIS I want to be able to use MODBUS to communicate with them as well as the existing EI-BISYNC methods.

Acceptance Criteria

1. The Eurotherm can be controlled via either comms protocol mentioned (EI-BISYNC, already existing, or MODBUS)
2. The Eurotherm 32h8i has been confirmed as either working with this IOC, or has had a ticket created to generate an IOC to talk with it

Notes

1. All existing Eurotherms can talk MODBUS as well as EI_BISYNC so this can be developed and tested against any Eurotherm
2. It may be needed if greater knowledge of the Quick Cooling Cryostat - Needle Valve Controller is required
3. It would allow the facility to stop ordering the Eurotherms with the extra comms protocol, which whilst not a large cost of itself is a significant proportional cost of each Eurotherm
4. We have a standard Eurotherm available to test with (I believe)
5. A request has been received to interact with a https://www.eurotherm.com/en/products/temperature-controllers-en/indicator-and-alarm-units-en/3200i-indicator-and-alarm-unit/ which uses ModBus RTU (https://www.eurotherm.com/?wpdmdl=27877) after the long shutdown
6. User Support have been asked as to whether or not they have a unit we could test with

[FreddieAkeroyd]

https://github.com/dls-controls/eurothermModbus might be of interest

[Tom-Willemsen]

Proposed as the long-term solution to #5756

[DominicOram]

Proposed so that we don't continually hotfix #5756

[FreddieAkeroyd]

Or we test replyTimout = 2000 elsewhere and then roll it out?

[FreddieAkeroyd]

Interestingly the DLS modbus driver calls modbusInterposeConfig to insert a 2000ms timeout...

[Tom-Willemsen]

PRs:

• Ticket4240 eurotherm modbus EPICS-ioc#718
• Ticket4240 eurotherm modbus EPICS-IOC_Test_Framework#556
• Ticket4240 eurotherm modbus EPICS-DeviceEmulator#150
• Ticket4240: modbus eurotherm #7293

Docs:

• https://github.com/ISISComputingGroup/ibex_developers_manual/wiki/Eurotherm

Follow-up issues:

• Eurotherm (modbus): find solution to scaling factors [Timebox: 4.5 days, 0.5 to review] #7345

Note: until #7345 has been done, we should prefer to use ei-bisynch comms to eurotherms wherever possible, as the current approach to scaling factors is very error-prone in subtle ways (e.g. wrong PID settings would make a eurotherm appear to talk correctly and may even change temperature ok for small changes, but would fail to change temperature during larger changes)

Note for reviewer: there are two eurotherms in the office you can test with - a 2000 series and a 3000 series. We had a third eurotherm but electronics have asked for this back before cycle.