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EPICS Signal Variants

BEC exposes three common EPICS-backed signal classes through ophyd_devices:

  • ophyd_devices.EpicsSignal
  • ophyd_devices.EpicsSignalRO
  • ophyd_devices.EpicsSignalWithRBV

Use these classes when you want to expose a single EPICS process variable in BEC instead of a full motor-style device.

Which one should I use?

The right choice depends on whether the PV is writable and how EPICS exposes its readback:

  • Choose ophyd_devices.EpicsSignal for a normal read/write signal.
  • Choose ophyd_devices.EpicsSignalRO for a read-only signal that BEC should monitor but never write to.
  • Choose ophyd_devices.EpicsSignalWithRBV when the EPICS record has a setpoint PV and a separate readback PV following the usual prefix and prefix_RBV pattern.

What goes into deviceConfig?

Each class expects a slightly different deviceConfig section in the BEC config:

  • ophyd_devices.EpicsSignal: read_pv, and optionally write_pv if the write PV differs from the read PV
  • ophyd_devices.EpicsSignalRO: read_pv
  • ophyd_devices.EpicsSignalWithRBV: prefix

What to remember

  • Use EPICS signal classes when you want to expose a single EPICS PV in BEC rather than a full motor device.
  • Choose EpicsSignal for read/write PVs, EpicsSignalRO for read-only PVs, and EpicsSignalWithRBV when setpoint and readback follow the usual RBV pattern.
  • The correct deviceConfig fields depend on the chosen class.
  • Picking the right EPICS signal variant keeps the BEC device model aligned with the underlying EPICS record behavior.