gta02-core and external GPS antenna

Werner Almesberger werner at
Sat May 30 16:22:59 CEST 2009

Steve Mosher wrote:
> Question: are you considering folding in the A8 changes? and the 1024 fix?
> beware on the A8 microphone as it requires an annoying case mod. doable,
> but annoying.

I definitely want the audio changes, yes, even beyond GTA02v8.
I.e., amplifier removal. I hope Joerg will have a look when we
get to the audio design and see if we missed anything.

The new EMI-hardened microphone sounds good, but I wonder if we
actually need it, if the existing buzz fix already solves all
issues without introducing new ones. Component availability may
also be an issue, perhaps even the deciding factor.

The #1024 fix would be easy to implement. Instead of adding
another ceramic capacitor, we could just use a sufficiently
large low-ESR tantalum cap, so the layout wouldn't even have to

The main problem with GSM at the moment is how we get the
design. The entire GSM side is non-public, schematics and
layout. I don't think Openmoko would have much of an issue with
releasing all this, but these things are under NDA with TI, so
TI would have to agree as well. We can knock on TI's door, but
I'm a little afraid they would have to recall people from
retirement to even know what that Calyoso thing is we're
talking about.

I'm also not sure if those NDAs are with Openmoko directly or
via FIC. Wolfgang probably knows.

An alternative would be if gta02-core could somehow license the
design from Openmoko and drop it in in a non-public way. Since
this would be the last gleaming of the whole Calypso complex
anyway, I wouldn't worry too much about the freedom aspects per
se. However, this would complicate handling the layout files on
the gta02-core side.

External GPS antenna connector removal seems to do more good
than harm. By simplifying the circuit and maybe cleaning up
some of the signals (I find the lack of filters on TX/RX a bit
irritating), we may very well recover a dB or two, making the
internal antenna almost as good as the external one.

- Werner

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