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fix: remove missplaced readme from aerotech

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appel_c 2024-03-21 19:48:41 +01:00
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## Integration log for the Ophyd integration for the Aerotech Automation1 EPICS IOC
This is a short collection of reverse engineered wisdom from integrating the first complex device to BEC. The integration involved both the ophyd part and the corresponding scan API. It might not be fully accurate and some issues are probably misdiagnosed.
## Avoid the safespace API!!!
The properly documented beamline scripting interface was meant for exernal users. Hence, it is idiotproof and only offers a very limited functionality, making it completely unsuitable for serious development. Anyhing more complicated should go through the undocumented scan API under 'bec/scan_server/scan_plugins'. The interface is a bit inconcvenient and there's no documentation, but there are sufficient code examples to get going, but it's quite picky about some small details (that are not documented). Note that the scan plugins will probably migrate to beamline repositories in the future.
## Differences to vanilla Bluesky
Unfortunately the BEC is not 100% compatible with Bluesky, thus some changes are also required from the ophyd layer.
### Event model
The BEC has it's own event model, that's different from vanilla Bluesky. Particularly every standard scan is framed between **stage --> ... --> complete --> unstage**. So:
- **Bluesky stepper**: configure --> stage --> Nx(trigger+read) --> unstage
- **Bluesky flyer**: configure --> kickoff --> complete --> collect
- **BEC stepper**: stage --> configure --> Nx(trigger+ read) --> complete --> unstage
- **BEC flyer**: stage --> configure --> kickoff --> complete --> complete --> unstage
What's more is that unless it's explicitly specified in the scan, **ALL** ophyd devices (even listeners) get staged and unstaged for every scan. This either makes device management mandatory or raises the need to explicitly prevent this in custom scans.
### The BEC hangs or deadlocks
Unfortunately a common behavior that manifests in . Common causes include the described issue with num_pos or raising an exception from the Ophyd layer. I'll expand this later.
### Class
The DeviceServer's instantiates the ophyd devices from a dictionary. Therefore all arguments of '__init__(self, ...)' must be explicity named, you can't use the shorthand '__init__(self, *args, **kwargs)'.
'''python
# Wrong example
#class aa1Controller(Device):
# def __init__(self, *args, **kwargs):
# super().__init__(*args, **kwargs)
# self._foo = "bar"
# Right example
class aa1Controller(Device):
def __init__(self, prefix="", *, name, kind=None, read_attrs=None, configuration_attrs=None, parent=None, **kwargs):
super().__init__(prefix=prefix, name=name, kind=kind, read_attrs=read_attrs, configuration_attrs=configuration_attrs, parent=parent, **kwargs)
self._foo = "bar"
'''
### Status objects (futures)
This is a major time sink. Bluesky usually just calls 'StatusBase.wait()', and it doesn't even check the type, i.e. it works with anything that resembles an ophyd future. However the BEC adds it's own subscription that has some inconveniences...
#### DeviceStatus must have a device
Since the BEC wants to subscribe to it, it needs a device to subscribe.
'''python
# Wrong example
# def complete(self):
# status = Status()
# return status
# Right example
def complete(self):
status = Status(self)
return status
'''
#### The device of the status shouldn't be a dynamically created object
For some reason it can't be a dynamically created ophyd object.
'''python
# Wrong example
# def complete(self):
# self.mon = EpicsSignal("PV-TO-MONITOR")
# status = SubscriptionStatus(self.mon, self._mon_cb, ...)
# return status
# Right example
def complete(self):
status = SubscriptionStatus(self.mon, self._mon_cb, ...)
return status
'''
### Collect does not yield
In Bluesky collect can be a generator, in BEC it should return the result.
### Scans
Important to know that 'ScanBase.num_pos' must be set to 1 at the end of the scan. Otherwise the bec_client will just hang.
'''python
class AeroScriptedSequence(FlyScanBase):
def __init__(self, *args, parameter: dict = None, **kwargs):
super().__init__(parameter=parameter, **kwargs)
self.num_pos = 0
def cleanup(self):
self.num_pos = 1
return super().cleanup()
'''
Note that is often set from a device progress that requires additional capability from the Ophyd device to report it's current progress.
'''
class ProggressMotor(EpicsMotor):
SUB_PROGRESS = "progress"
def __init__(self, prefix="", *, name, kind=None, read_attrs=None, configuration_attrs=None, parent=None, **kwargs):
super().__init__(prefix=prefix, name=name, kind=kind, read_attrs=read_attrs, configuration_attrs=configuration_attrs, parent=parent, **kwargs)
self.subscribe(self._progress_update, run=False)
def _progress_update(self, value, **kwargs) -> None:
"""Progress update on the scan"""
if not self.moving:
self._run_subs( sub_type="progress", value=1, max_value=1, done=1, )
else:
progress = np.abs( (value-self._startPosition)/(self._targetPosition-self._startPosition) )
self._run_subs(sub_type="progress", value=progress, max_value=1, done=np.isclose(1, progress, 1e-3) )
'''
calculated
Otherwise