2. Use ophyd-async

Status

Current

Context

We need to decide whether to use ophyd or ophyd-async as our bluesky device abstraction layer.

Docs

Source

PyPi

ophyd

Docs

Source

PyPi

ophyd-async

Docs

Source

PyPi

ophyd has been the default device abstraction layer for bluesky EPICS devices for some time.

ophyd-async is a newer (and therefore less mature) device abstraction layer, with similar concepts to ophyd. It has been implemented primarily by DLS.

The primary differences which are relevant for ISIS are:

  • In ophyd-async many functions are implemented as asyncio coroutines.

  • ophyd-async has better support for non-channel-access backends (notably, PVA)

  • Reduction in boilerplate

Present

Tom & Kathryn

Decision

We will use ophyd-async.

Consequences

  • ophyd-async will allow us to use PVAccess easily.

  • ophyd-async will allow us to do fly scanning, if required in future, more easily than ophyd

  • Developers will need to understand more details about asyncio

  • Developers will have to write somewhat less boilerplate code in ophyd-async as compared to ophyd

  • Our devices should be more comparable to other facilities on site (e.g. DLS) who are using ophyd-async.