README  DAQ plugin

Nov. 27, 2012  David Lawrence

This directory contains files for the DAQ plugin which is used
to read in EVIO formatted data obtained from the Hall-D data
acquisition system. The plugin will read in from either an ET
system or an EVIO formatted file, parsing the input and creating
low-level hit objects.

At this time, the Hall-D DAQ system does not yet exist, but a 
library, mc2coda, does that can convert Simulated data into
the EVIO format we expect the DAQ system to deliver.

The structure of the code has the bulk of the difficult work
being done in the JEventSource_EVIO class. The JEventSource_FileEVIO
and JEventSource_ETEVIO classes derive from this, but only
to instantiate different subclasses of evioChannel. The ET system
may require creation of a station. In addition there is talk
of packaging multiple EVIO events into a single ET buffer which
might require additional handling.


Dec. 18, 2012 DL

Updated to use new evioETChannel to get events from ET system.
A few notes on this:

1. The "new" system that Carl and Elliott are planning is to
wrap multiple EVIO events in a single ET event to reduce
overhead. The evioETChannel assumes this is done and so
unwraps them. This means events must be inserted into the
ET system with this wrapping. Elliott has provided a program
that does this call "montest". It consists of a single source
file that can be found here: /group/halld-online/montest/montest.cc

2. ET and EVIO distributions have been compiled on CentOS5
in the halld group area. In particular, the prototype EVIO
version with the evioETChannel class.

3. Here's how to start up a system that worked on ifarm1101:

- Set a SESSION environment variable to something unique to
  your job (e.g. DAVIDL) and start the et system:
  
  et_start


- In a different window, start montest to feed events from an
  evio file into the ET system:
  
  ./montest -et_file /tmp/et_sys_DAVIDL rawevent_000002.evio
  

- Start the JANA program with the DAQ plugin and the ET source
  specified using the session name:
  
  hd_ana -PPLUGINS=DAQ ET:DAVIDL


- If you want to monitor the ET system, use the et_monitor program

  et_monitor -f /tmp/et_sys_DAVIDL -t 2