Chapter 3. DDAS Data unpackers.

DDAS data are broken up into hits. A hit is the data from a single channel of DDAS. You can think of the DDAS readout software as delivering a stream of these hits. The SpecTcl DDAS software provides two event processors that can be used with SpecTcl. These are:

• DAQ::DDAS::CParameterUnpacker which processes raw DDAS hits. These are the units of data that come from a single DDAS channel. In the absence of an event builder to glue hits within some coincidence time intervale, events from DDAS look like events containing single hits.

  In general you will not want to use this unless you are taking singles data.

• DAQ::DDAS::CDDASBuiltUnpacker processes the output of the NSCLDAQ event builder. Hits that satisfy the event builder's coincidence window are treated as a single event.

Both of these unpackers rely on you to provide a mapping between hits and SpecTcl parameters. This mapping is performed by supplying an object from a class derived from DAQ::DDAS::CParameterMapper.

The derived class must implement the method:

This method is expected to unpack the elements of the hits vector into parameters in rEvent. Naturally CTreeParameter objects can be used instead to manage this unpacking.

The constructors for the two unpackers are shown below along with a simple example that sets up the event built unpacker within MySpecTclApp.cpp

Assume that MyParameterMapper is a class that's implemented to unpack its from DDAS for our experiment. The MySpecTclApp::CreateAnalysisPipeline method body might look like this:

MyParameterMapper mapper;
std::set<uint32_t>  ddasIds = {1, 2, 3};   // Allowed DDAS source ids (crates).
...
MySpecTclApp::CreateAnalysisPipeline(CAnalyzer& rAnalyzer)
{
    RegisterEventProcessor(*(new DAQ::DDAS::CDDASBuiltUnpacker(ddasIds, mapper)));
}