EVBLite is an event builder that can be used in the following circumstances:
You have a single data source of ordered fragments. Examples include single crate XIA systems, and single CoBo GET systems.
You don't require a graphical user interface that shows event builder statistics.
You have high rates that may stress or saturate the normal NSCLDAQ event builder.
EVBLite was introduced with NSCLDAQ version 12.0.
The best way to understand EVBLite is to dissect the normal NSCLDAQ event builder the compare and contrast EVBLite with it.
The NSCLDAQ event builder consists of a unix pipe. The members of that pipe are:
Accepts connections from several data sources. The ordered fragments from these data sources are then output in a totally ordered stream of fragments. Fragments consist of a header that contains, among other things, the fragment timestamp and the payload, which is just the data from the original data source.
Orderer data sources are TCP/IP clients, usually RingFragmentSource programs. These data sources send blocks of fragments to the Orderer over socket connections.
Glom accepts fragments on stdin created by the Orderer. Glom's primary function is to glue together physics event fragments that occur within a coincidence interval into events. Thus it's really glom that is performing the function of event building.
Glom outputs events to its stdout as NSLCDAQ ring items.
This simple program just accepts data on stdin and puts it into an NSCLDAQ ringbuffer.
Since Glom is a filter (stdin to stdout), if the orderer program were replaced by any other program that produces a stream of ordered fragments with the correct event builder headers, it will happily build events from that data stream. The single data source EVBLite works with therefore simply needs a tagger - a program that takes a stream of ring items from its single data source, prepends the appropriate headers and psses the resulting fragments to stdout.
EVBLite is therefore a linux pipe consisting of::
A standard NSCLDAQ program that ouptputs data from a ringbuffer to its stdout. It is the source of data for EVBLite
Accepts a stream of ring items on its stdin and produces an output stream consisting of those ring items prepended with the appropriate fragment headers.
As with the full event builder, glom produces a stream of event ring items.
As before stdintoring puts the output from glom into an NSCLDAQ ringbuffer.
EVBLite also provides a Tcl package that can be used to define and start the EVBLite event building pipeline from e.g. ReadoutCallouts.tcl or a sequence step in the program manager.