Beckhoff: Engineering units are left at microns by default

[rerpha]

As a scientist I would like my Beckhoff to tell me what its engineering units are through IBEX. I identified when commissioning LARMOR that the units for the system were incorrect. The units should be deg for LARMOR as it's a rotating bench, however by default we display um as the EGU. We should talk to the motion team about how we can add this functionality.

Acceptance Criteria

What is the acceptance criteria?

• A discussion is had between us and the motion team about adding this functionality.
• Changes are implemented in tcioc for the units info to propagate to each axis (units may also be different per axis?)
• Tests are added to make sure this info is propagated correctly

Extra Information

This information currently isn't stored in the status struct, or subsequently the .tpy file. It may be best to add these through the global struct instead, for example how nAXIS_NUM is added (even though we don't currently use it!)

[rerpha]

units are passed through via https://github.com/ISISComputingGroup/EPICS-ioc/blob/master/TWINCAT/TWINCAT-IOC-01App/Db/single_axis.substitutions - this will be tricky to do as obtaining info before ioc startup is hard to do in the st-common

we could rethink how we actually load stuff in from the st-common, such as doing an iocinit for certain pvs serving the global vars, im not sure if this is possible or not

[DominicOram]

It may be that we can read it through the motor record. It is possible to change it at runtime