Engines

An MxDC Engine is an object which manages common operations involving multiple devices. Engines can spawn threads to run operations asynchronously as needed.

All engines in MxDC are derived from the base class mxdc.Engine which provides a default set of methods attributes and signals for all device types. Specific Engines types can be created by subclassing mxdc.Engine and adding required methods, signals and attributes.

class mxdc.Engine

Base class for all Engines.

An Engine provides utilities for running stoppable/pausable activities in a thread, reporting progress and notifying watchers of the start, end and progress of the activity

Signals

  • started: arg_types=(data: object,)

  • stopped: arg_types=(data: object,)

  • busy: arg_types=(bool,)

  • done: arg_types=(data: object,)

  • error: arg_types=(str,)

  • paused: arg_types=(paused: bool, reason: str)

  • progress: arg_types=(fraction: float, message: str)

Attributes

  • beamline: Beamline Object

execute()

Run engine in the current thread :return: the result of the run method

is_busy()

Check if the engine is busy

is_paused()

Check if the engine is paused

is_stopped()

Check if the engine is stopped

pause(reason='')

Pause the engine

Parameters

reason – Optional string describing the reason for the pause

resume()

Resume from the paused state

run()

This method should contain the implementation details of the engine operation. It should appropriately monitor the stopped and paused variables and act accordingly.

start()

Start the engine as a daemon thread

stop()

Stop the engine

The following are some examples of engines included by default.

class mxdc.engines.scanning.BasicScan

Base Class for all Scan engines.

Signals

  • new-point: (object,) new scan point

  • new-row: (int,) new scan row for multi-row scans

  • message: (str,) messages

configure(**kwargs)

Set configuration parameters

Parameters

kwargs – keyword, value pairs to add to configuration

Returns

config object, fields are dictionary keywords

extend(amount)

Extend the scan by the given amount. Subclasses should update the configuration before calling the base class extend() method since this method will start the scan.

Parameters

amount – amount to extend scan by

finalize()

Convert the data after the scan is complete and finalize before wrapping up

Parameters

data – a list of tuples representing the acquired data

get_specs()

Get the scan specification describing the scan and scan data

Returns

dictionary

prepare_xdi()

Prepare XDI file for saving

Returns

xdi_data object

run()

Run the scan in the current execution loop. Normally executed in a thread when the start method is called. Sub-classes are discouraged from re-implementing this method. Instead override the scan() method.

save(filename=None)

Save the scan data.

Parameters

filename – full path to data file. If None, a file name will be generated.

Returns

the file name of the saved file

scan()

Scan implementation. Details must be implemented by sub-classes

setup(motors, counters, i0=None)

Setup scan data configuration

Parameters
  • motors – sequence of motors

  • counters – sequence of counters

  • i0 – reference counter

start()

Start the scan engine