Trigger/Gate API reference

The trigger/gate element represents synchronization devices like for example the digital trigger and/or gate generators that are used to synchronize the experimental channels.

Trigger or gate characteristics could be described in either the time and/or the position configuration domains.

Time domain

In the time domain, elements are configured in time units (seconds) and generation of the synchronization signals is based on passing time.

Position domain

The concept of position domain is based on the relation between the trigger/gate and the moveable element. In the position domain, elements are configured in distance units of the moveable element configured as the feedback source (this could be mm, mrad, degrees, etc.). In this case generation of the synchronization signals is based on receiving updates from the source.

There exist different types of hardware capable to synchronize in position domain by means of processing encoder signals and generating synchronization signals:

Motion controllers e.g. IcePAP, Pmac, etc.
Versatile controllers e.g. Pandabox, PiLC, etc.

These devices consist of set of inputs (encoders signals) and outputs (synchronization signals) and usually can work in two modes, where:

coupled mode - one input is coupled to one output
multiplexor mode - many inputs may produce synchronization signals on many outputs

Each trigger/gate element supporting position domain must be configured with MoveableOnInput attribute which value should reflect the hardware connection between the moveable feedback signal (encoder) and the trigger/gate input id. An optional default key _ (underscore) can be used to enable generic behavior without requiring an explicit mapping between the moveable’s encoder signal This default value will be used for time-based scans (for example timescan) or for scans with a moveable that is not explicitly present as a key in the trigger/gate MoveableOnInput attribute, enabling a default behavior.

Attributes

A trigger/gate has a state, and a index attributes. The state indicates at any time if the trigger/gate is stopped, in alarm or moving. The index, indicates the current trigger/gate index.

Trigger/gate elements will also have:

moveable_on_input

Its value differs depending on the supported mode of a given trigger/gate element:

for the coupled mode it is a name or full name (str) of the moveable which encoder is connected to the input
for the multiplexor mode it is a dict mapping names or full names (str) of moveables which encoders are connected on inputs to the inputs’ IDs (int)