OpenMHS family: bluesky-ophyd

Classic Ophyd Devices through OphydDriver

Generated by MHS/registry/build_registry.py on 2026-10-20T00:00:00Z from 28 registry records and their task cards. A plan, not a conformance claim.

• bridge_status: available
• helper: OphydDriver
• exemplar: MHS/drivers/labs/bcda-aps__apstools

Launch

Every driver package starts the same way; per-repo configuration (environment id, model path, port, baud rate, VISA resource) lives in the package's driver.py, never in launch flags:

mhs serve <driver-dir>

A package is done when python3 -m mhs.driver check <driver-dir> --backend fake exits 0 (evidence contract_checked; a fake never yields an MHS-Device level).

Registry coverage

• Repos: 28
• Decisions: bridge-runtime 4, family-config 3, reference 7, skip 14
• Waves: 2: 1, 3: 1, 5: 1, 9: 25
• Dispatchable now: 0
• Modes: hardware 7, simulated 5

Applicability

Classic (synchronous) Ophyd Devices: triage rule 9, family:ophyd. OphydDriver is a configuration-only helper over the Python-object bridge. Each field is a Field in parameters plus one signal_bindings entry: signal (a direct Component attribute of the card's entry class), get: True, set (equal to Field.writable), profile, get_kwargs, timeout_ms (1..60000) and source_ref (the path:LINE of the Component assignment). Profiles: classic_epics_v1 (Component(EpicsSignal, ...): get, and a set that waits for its Status), classic_epics_ro_v1 (Component(EpicsSignalRO, ...): get only) and classic_soft_v1 (Component(Signal, ...), get_kwargs {}). Both EPICS profiles read with get(use_monitor=False) and require exactly that get_kwargs. Gate G7 proves each declaration in the pinned source without importing Ophyd, and refuses any other dotted member the fake or the driver touches (OPHYD_UNPROVEN_MEMBER).

The apstools exemplar is a read-only R0 monitor: seven EpicsSignalRO fields of ApsMachineParametersDevice, one observational x-cap capability whose native is the proven current.get, a source-shaped fake and a hardware factory that builds the upstream Device. It shows the declaration grammar, the fake and the facts; it does not demonstrate a write, a Status or a native stop. The Ophyd driver guide gives the complete contract.

Capability mapping

Class ids come from python3 -m mhs.driver catalog search <words>. The deprecated classes cap.device.describe.v1, cap.world.state.v1, cap.world.snapshot.v1 and cap.world.restore.v1 are replaced by the protocol methods mhs.devices.get, mhs.resource.read, mhs.snapshot and mhs.restore.

Safety

The risk floor of a device is the highest catalogue risk_class of its classes (CAP-017); a driver may declare a higher risk, never a lower one. Hardware at R1 or above needs a native stop (safety_bindings.estop) and a non-empty safe state. Ophyd Devices front motors, shutters, detectors and high-voltage supplies: risk follows the hazard table of the safety specification, not the card's floor, and a model-authored R2 or R3 package never runs its hardware backend before a human signs reviewed_by. A Device's generic stop() is not evidence that anything physical stopped. EPICS drive limits, validators and PV metadata read at run time are not sourced limits.

Fidelity

A source-shaped fake holds one stand-in object per bound Component that implements only the calls the driver makes (get(use_monitor=...), and set(value) returning a Status for a writable binding); its values are placeholders and it runs no IOC. It yields contract_checked evidence only: Channel Access, PV connection and record processing are not modelled.

Pitfalls

EPICS PV names are deployment-specific; area detectors produce large arrays (NEEDS_ARTIFACTS); startup-script profile collections are not Device classes. A class body with executable statements, decorators, metaclasses, reflection or receiver escapes fails the source proof even when its Components look simple.

First task cards

• gh.diamondlightsource/dodal: family-config, wave 2, rank 8, MHS/registry/tasks/labs/diamondlightsource__dodal.json
• gh.bcda-aps/apstools: family-config, wave 3, rank 22, MHS/registry/tasks/labs/bcda-aps__apstools.json
• gh.bec-project/ophyd_devices: family-config, wave 5, rank 15, MHS/registry/tasks/labs/bec-project__ophyd_devices.json
• gh.bluesky/ophyd: bridge-runtime, wave 9, rank 46, MHS/registry/tasks/labs/bluesky__ophyd.json
• gh.bluesky/ophyd-async: bridge-runtime, wave 9, rank 58, MHS/registry/tasks/labs/bluesky__ophyd-async.json

Sources

• Task cards: MHS/registry/tasks/<track>/<owner>__<repo>.json (schema/taskcard.schema.json).
• Triage rules and the helper table: MHS/registry/triage.py; curated decisions: MHS/registry/overrides/.
• Driver API and gate: MHS/sdk/docs/driver-authoring.md; exemplars: MHS/drivers/.
• Ophyd driver contract and driver authoring.
• apstools exemplar fake, tests, source facts and result/evidence scope.