Event builder readout callouts allow you to integrate the event builder with the Readout GUI. There are three layers of callouts;
An API layer provides the highest level of flexbility by providing you witha set of Tcl procs you can use from inside your ReadoutCallouts Extensions to manage the event builder and its pipeline.
A ReadoutGUI state machine callout bundle that allows you to register and configure the event builder and to let the state machine callbacks take care of everything for you. This is the preferred way to integrate the event builder into your experiment.
An EZBuilder layer provides a set of simple calls you can make from your ReadoutGUI ReadoutCallous.tcl script. Unless you have special needs, there is no reason to use this over the state machine callout bundle.
All of these layers are part of the Tcl package evbcallouts