[time-nuts] Form Factor and such, Big Picture

[Chris Albertson]

I think you have the idea, especially the part about needing only a
very few wires between the daughter boards.   But if that is the case
why have a motherboard and what do you do with an FPGA?

So my idea is that daughter cards each go in a small aluminum box of
their own and connect between boxes with, as you say "just a few
wires".  One or more of these boxes would connect to analog signals to
be measured and at least one of the boxes would provide an interface
to a computer or to a human.

I think it is agreed not to use any part that has a BGA.  Use only
parts that can be hand soldered.

I do think they all can fit on the same 100x160mm size PCB because if
a module to so complex that it can't fit, it can be split ion half and
use two PCBs.

On Wed, Dec 22, 2010 at 4:40 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
>
> I think I'm missing the big picture.  What sort of things are people
> interested in building?  Will they all be a reasonable fit with a single Form
> Factor, Bus, and whatever?
>
> I've been thinking of something like a mother board with FPGA that would fit
> in something like the Hammond boxes.  The idea is that the FPGA is the part
> that's hard for me because I can't handle soldering BGAs.  All the front-end
> analog stuff would go on a daughter card.
>
> The hardware interface between the mother/daughter cards is just a row (or 3)
> of pins/sockets for 0.1 inch connectors.  (or anything similar)   Software
> interface is TBD.  It might make sense to publish a "standard" interface for
> some application so the same firmware on the motherboard would work for
> various front ends.
>
> It might make sense to put an ARM next to the FPGA.  You can get a lot of CPU
> for $10-20.
>
> I'm not sure what the back end sould look like.  I'd be happy with USB or
> Serial.  They are dumb/simple and don't require massive protocol stacks.  I
> could live with Ethernet, but it really raises the bar for getting off the
> ground.   (I'm not interested in running a web server on my toys.  All I want
> is simple command/response.  I'll put the web server on a PC that has access
> to all the archived data.)
>
> It might make sense to have a back-end daughter card.
>
>
> With that sort of setup, I think I could build a 5370 class box that I could
> use for long term data collection.  Does that seem reasonable?
>
> I don't need the full flexibility of the 5370 front end.  I'm willing to use
> jumpers or a soldering iron for things like AC vs DC coupling and 50 ohm
> termination.
>
>
> On the other hand, how much board space would a spectrum analyzer take?
> Should we be discussing 2 sizes of projects?
>
>
>
>
> --
> These are my opinions, not necessarily my employer's.  I hate spam.
>
>
>
>
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-- 
=====
Chris Albertson
Redondo Beach, California