[Gb-ccb] 17feb04 CCB telecon minutes

[Brian Mason]

17feb04  Telecon

present: Tim Pearson, Martin Shepherd; Chuck Niday, Randy McCullough,
Brian Mason, Melinda Mello

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Agenda
I-update on GB progress (detector circuit prototype status)
II-update on CIT progress (FPGA/USB/...)
III-discussion of the 4-board design proposal (pro & con)
IV-assorted other issues (software, etc)

SUMMARY OF RESULTING ACTION ITEMS
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*Consider 4-FPGA synchronization & communication issues and determine
if there are any showstoppers there, if we need control signals
distributed between FPGAs, etc. (MCS)

*Review Cesys spartan-2 board's datasheets and see if it's USB2
interface will do what we need it to without too much FPGA
programming, and if there are other currently unidentified
showstoppers lurking. (MCS/RM)

*Investigate availability of suitable SBC computers that implement
USB2 ports (MCS)

*Examine Cesys spartan-2 pricetag -vs- budget (TJP); assume
N=4+3+spare+dev't (?)

*Review CCB Use cases (TJP; BSM & MM)

*Get Michael on track with the manager, & Martin's simulator (MM & BSM)

*Determine how to do response time tests on detector circuit (RM/CN)

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Detailed Meeting Minutes

I- Randy reported on the detector circuit development effort here.
Status is: circuit board has been designed, ordered, and received (4
units); the TTE bessel filters have arrived unexpectedly quickly (4
units also); and we are in the process of acquiring assorted other
needed parts.  We expect to assemble next week and will be considering
how to test the step resonse and other dynamical aspects (first tests
will be static tests of range, linearity, levels, etc).

II- Martin has been working on getting up the FPGA programming curve,
and has completed a 1-channel data pipeline prototype (and, I believe,
successfully simulated it).  It is not clear where they are on the
timeline which has the FPGA program done by end-of-March; this largely
depends on sorting out architecture and computer interface issues.


III- We went through Martin's list of concerns re: Randy's 4-FPGA
spartan 3 design.  Some notable points raised were as follows.  1) The
clear and unanimously agreed upon prime concern is the actual
achievable USB communication rate with the computer. 2) Martin is
concerned about having 4 independent FPGAs synchronized only by 1pps
and 10 MHz, and would rather see control signals redistributed to each
FPGA.  We didn't resolve this one and it bears more consideration.  3)
Availability of a single-board computer which implements USB2.0 is
another potential issue which needs to be looked into.  4) As to why
there is an extra enclosure around the Analog/FPGA unit, Randy
indicated this was chosen with other possible applications in mind
(this isn't a critical issue for the scheme either way); 5) the
question of how filtering will be done between the FPGA and the ADC
was raised.  Randy indicated surface mount pi filters could be used,
with the addition of little cans soldered over the sensitive analog
bits if needed.

We briefly discussed the new Cesys spartan-2 board Randy has found (to
possibly replace the spartan-3 development board).  This has fewer
gates (but 1 MB onboard fast RAM which may offset the loss), and
probably enough inputs per FPGA.  The main advantage of this board is
that it advertises fully implemented USB2.0 , although we need to
carefully examine the datasheets to determine what the FPGA interface
is and what sort of datarates we expect to achieve in practice with
it.  It doesn't seem there are clock multipliers on the spartan-2
which is a disadvantage (harder to use an external clock reference).
The price (~$750) also needs to be considered.  If the price and USB
factors aren't prohibitive we can probably go this route, though this
isn't a given now.

IV- Other

*Tim indicated that Christobal Acherman still plans to arrive at the
end of March.

*Brian filled in CIT as to the plans to have Michael work on the YGOR
manager. Melinda Mello will be helping in this.



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Brian Mason                           | office: +1(304)456-2338
Assistant Scientist                   | fax:    +1(304)456-2229
National Radio Astronomy Observatory  | mail:   PO Box 2 
bmason at gb.nrao.edu                    |         Green Bank, WV 24944
http://www.gb.nrao.edu/~bmason/       |
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