21/07/2004 23:57:36, Jamie Morken <jmorken@shaw.ca>
wrote:
>I think the PXA27x series is great too :)  The only problem I have
heard
>about it is that
>it may be a short production run and thus may not be available
for very
>long,

Yeah - none of these processors have the longevity of, say, a Z80,
but that's one of the things that the Balloon concept is trying to
protect people from - the connector should stay (more or less) the
same, regardless of how many times we're forced to upgrade the
CPU.

>I like the PXA271 the best as it has 32MB sdram and 32MB flash
built
>in to it.  I don't
>think this is enough sdram for most people but it is tempting to
avoid the
>external ram and flash
>interfaces and make a simple board with just the power and
JTAG routed and
>SPI/I2C and
>have a high performance 32bit controller for embedded
projects like
>robotics!

Yeah. If you were to do that, I'd be tempted to add the fast serial
link to an external FPGA, too. It's not many pins, but gets you a
nicely general purpose lump of whatever hardware you want,
witout tying up CPU resources. (The PXA may clock like a mad
thing, but it'd be a shame to waste all that speed trying to make it
run PWM channels or whatever else needs hard real-time. Caches
also make such things less deterministic than you'd hope...). You'd
also need to supply power, buffers, reset control, clocks, etc. and
then the temptation to just add connectors for the LCD and
keypad would be overwhelming. After that, it's only a couple of
steps to a full-blown balloon :)

>and the pin pitch
>is really quite small (0.65mm)

Yeah, it's tight, and would need a decent PCB, but 0.65mm isn't in
microvia land, it's just very small normal vias. Still, it'll need to be
a proper 4-layer jobbie, no bathtub etching fot that CPU...

>I am
>interested in helping out
>(if you are accepting volunteers!)

it's not clear how to get volounteers roped in for this - it's easier if
they have access to Protel CAD tools, or can export something I
can import.  At the moment, I think Im jst scrounging for ideas,
and the implementation is my problem...

Steve