[Pafgbt] PAF/GBT code

[Rick Fisher]

Hi Richard,

It's been awhile since we last communicated on PAF/DAQ so just thought I'd 
touch base to take stock.  Aside from a question on whether the DC channel 
was counted in the spectral channel count, I think we had pretty well 
converged on my understanding of the streaming data packet format.  I've 
started rounding up some code to write a data display for this format 
that might help with data integrity checks at the beginning of a data 
acquisition session.

It looks like section 4.3 of your documentation spells out what we need to 
control the streaming mode.  That will be next on our TODO list and will 
be the beginning of writing the "Modification Request" that we need to 
provide to the GBT control system programmers.

I think that your data acquisition mode of greatest interest for tests of 
the beamforming array on the telescope will be the Correlator.  Data from 
this mode allows us to calibrate the array and gives us the most 
information about array performance and anomalies.  How far along are you 
in bench testing and documentation of this mode?  When you have some 
sample data from the correlator we can start writing a software reader on 
our end.  The streaming data sample that you provided was really 
instructive.

Dr. Jeffs may have told me this and I've since forgotten, but are you 
building two copies of the data acquisition hardware (one for development 
and one to go to either Green Bank or Arecibo as needed) or just one? 
Quite some time ago we received a list of components that went into your 
system, but we haven't thought much more about whether we should invest in 
a copy of this hardware.  We should give this more thought now that it's 
clearer who is available here to work on that part of the project.

Best regards,
Rick