pcdsdevices.state.StatePositioner

class pcdsdevices.state.StatePositioner(prefix, *, name, **kwargs)

Base class for state-based positioners.

Positioner that moves between discrete states rather than along a continuous axis.

Parameters:

• prefix (str) – The EPICS PV prefix for this motor.

• name (str) – An identifying name for this motor.

• settle_time (float, optional) – The amount of extra time to wait before interpreting a move as done.

• timeout (float, optional) – The amount of time to wait before automatically marking a long in-progress move as failed.

state

This signal is the final authority on what state the object is in.

Type:

Signal

states_list

This no longer has to be provided if the state signal contains enum information, like an EPICS mbbi. If it is provided, it must be an exhaustive list of all possible states. This should be overridden in a subclass. ‘Unknown’ must be omitted in the class definition and will be added dynamically in position 0 when the object is created.

Type:

list of str

states_enum

An enum that represents all possible states. This will be constructed for the user based on the contents of states_list and _states_alias, but it can also be overriden in a child class.

Type:

Enum

_invalid_states

States that cannot be moved to. This can be optionally overriden to be extended in a subclass. The _unknown state will be included automatically.

Type:

list of str

_unknown

The name of the unknown state, defaulting to ‘Unknown’. This can be set to False if there is no unknown state.

Type:

str

_states_alias

Mapping of state names to lists of acceptable aliases. This can optionally be overriden in a child class.

Type:

dict

Methods

camonitor()

Shows a live-updating motor position in the terminal.

This will be the value that is returned by the position attribute.

This method ends cleanly at a ctrl+c or after a call to end_monitor_thread(), which may be useful when this is called in a background thread.

configure(d: Dict[str, Any]) → Tuple[Dict[str, Any], Dict[str, Any]]

Configure the device for something during a run

This default implementation allows the user to change any of the configuration_attrs. Subclasses might override this to perform additional input validation, cleanup, etc.

Parameters:

d (dict) – The configuration dictionary. To specify the order that the changes should be made, use an OrderedDict.

Returns:

• (old, new) tuple of dictionaries

• Where old and new are pre- and post-configure configuration states.

describe() → OrderedDictType[str, Dict[str, Any]]

Provide schema and meta-data for read().

This keys in the OrderedDict this method returns must match the keys in the OrderedDict return by read().

This provides schema related information, (ex shape, dtype), the source (ex PV name), and if available, units, limits, precision etc.

Returns:

data_keys (OrderedDict) – The keys must be strings and the values must be dict-like with the event_model.event_descriptor.data_key schema.

end_monitor_thread()

Stop a camonitor() or wm_update() that is running in another thread.

get(**kwargs)

Get the value of all components in the device

Keyword arguments are passed onto each signal.get(). Components beginning with an underscore will not be included.

get_state(value)

Given an integer or string value, return the proper state entry.

Returns:

state (~enum.Enum) – The corresponding Enum entry for this value. It has two meaningful fields, name and value.

move(position, moved_cb=None, timeout=None, wait=False)

Move to the desired state and return completion information.

Parameters:

• position (int or str) – The enumerate state or the corresponding integer.

• moved_cb (callable, optional) – Function to call at the end of motion. i.e. moved_cb(obj=self) will be called when move is complete.

• timeout (int or float, optional) – Move timeout in seconds.

• wait (bool, optional) – If True, do not return until the motion has completed.

Returns:

status (StateStatus) – Status object that represents the move’s progress.

mv(position, timeout=None, wait=False, log=True)

Absolute move to a position.

Parameters:

• position – Desired end position.

• timeout (float, optional) – If provided, the mover will throw an error if motion takes longer than timeout to complete. If omitted, the mover’s default timeout will be use.

• wait (bool, optional) – If True, wait for motion completion before returning. Defaults to False.

• log (bool, optional) – If True, logs the move at INFO level.

post_elog_status()

Post device status to the primary elog, if possible.

read() → OrderedDictType[str, Dict[str, Any]]

Read data from the device.

This method is expected to be as instantaneous as possible, with any substantial acquisition time taken care of in trigger().

The OrderedDict returned by this method must have identical keys (in the same order) as the OrderedDict returned by describe().

By convention, the first key in the return is the ‘primary’ key and maybe used by heuristics in bluesky.

The values in the ordered dictionary must be dict (-likes) with the keys {'value', 'timestamp'}. The 'value' may have any type, the timestamp must be a float UNIX epoch timestamp in UTC.

Returns:

data (OrderedDict) – The keys must be strings and the values must be dict-like with the keys {'value', 'timestamp'}

read_configuration() → OrderedDictType[str, Dict[str, Any]]

Dictionary mapping names to value dicts with keys: value, timestamp

To control which fields are included, change the Component kinds on the device, or modify the configuration_attrs list.

screen()

Open a screen for controlling the device.

Default behavior is the typhos screen, but this method can be overridden for more specialized screens.

set(position, moved_cb=None, timeout=None)

Move to the desired state and return completion information.

This is the bare-bones implementation of the move with only motion, callbacks, and timeouts defined. Additional functional options are relegated to the move command and bells and whistles are relegated to a different interface.

Parameters:

• position (int or str) – The enumerate state or the corresponding integer.

• moved_cb (callable, optional) – Function to call at the end of motion. i.e. moved_cb(obj=self) will be called when move is complete.

• timeout (int or float, optional) – Move timeout in seconds.

Returns:

status (StateStatus) – Status object that represents the move’s progress.

classmethod set_defaults(*, connection_timeout=10.0)

Set class-wide defaults for device communications

This may be called only before any instances of Device are made.

This setting applies to the class it is called on and all its subclasses. For example,

>>> Device.set_defaults(...)

will apply to any Device subclass.

Parameters:

connection_timeout (float, optional) – Time (seconds) allocated for establishing a connection with the IOC.

Raises:

RuntimeError – If called after EpicsSignalBase has been instantiated for the first time.

status() → str

Returns a str with the current pv values for the device.

summary()

trigger() → StatusBase

Trigger the device and return status object.

This method is responsible for implementing ‘trigger’ or ‘acquire’ functionality of this device.

If there is an appreciable time between triggering the device and it being able to be read (via the read() method) then this method is also responsible for arranging that the StatusBase object returned by this method is notified when the device is ready to be read.

If there is no delay between triggering and being readable, then this method must return a StatusBase object which is already completed.

Returns:

status (StatusBase) – StatusBase object which will be marked as complete when the device is ready to be read.

wait(timeout=None)

wm()

Get the mover’s current positon (where motor).

wm_update()

Shows a live-updating motor position in the terminal.

This will be the value that is returned by the position attribute.

This method ends cleanly at a ctrl+c or after a call to end_monitor_thread(), which may be useful when this is called in a background thread.

Attributes

configuration_attrs

connected

connection_timeout

egu = 'state'

high_limit

hints

kind

limits

low_limit

moving

Whether or not the motor is moving

Returns:

moving (bool)

position

Name of the positioner’s current state. If aliases were provided, the first alias will be used instead of the base name.

settle_time

Amount of time to wait after moves to report status completion

state = None

states_list = []

stop

Hide the stop method behind an AttributeError.

This makes it so that other interfaces know that the stop method can’t be run without needing to run it to find out.

subscriptions: ClassVar[FrozenSet[str]] = frozenset({'_req_done', 'acq_done', 'done_moving', 'readback', 'start_moving', 'state'})

timeout

Amount of time to wait before to considering a motion as failed