[Freerunner] Access GPS chip's parameters and navigational models?

Daniel Willmann daniel at openmoko.org
Sun Mar 1 19:57:22 CET 2009

On Wed, 14 Jan 2009 18:18:26 +0100
Olivier Migeot <larrycow at gmail.com> wrote:

> I'm currently experimenting things with the Antaris chip, and I'm
> starting to like it - at least through FSO and it's gpsd compatibility
> layer. I've been browsing through the UBX protocol specification, and
> I stumbled upon one interesting parameter : the dynamic platform model
> of the navigational unit.
> Simply put : using this, we should be able to explain our chip that we
> are either by car or by foot, and get more serious tracklogs
> (providing this is doable, 'cause the doc states "(SW Versions 3.04
> and higher)", so I'm not sure whether or not we qualify).

Changing the dynamics model is working with our chip. Adding a
configuration interface for ogpsd to change these and similar settings
has been on my list for some time. Since I'm done with with this
semester's exams and SMS seems to be almost done I'll be
thinking/working on this during March.

> Hoping that we do (well, ignoring that maybe we don't, actually), I
> tried to feed the setting to the chip. The CFG-NAV2 UBX message that
> does that is 40 bytes long, and contains loooot of more or less
> related information, which I certainly don't know how to feed. So I
> tried to first _get_ the setting, and re-set it verbatim (give or take
> the said parameter). But though there is a tool to generate UBX
> messages (ubxgen.py, on
> http://wiki.openmoko.org/wiki/Neo_FreeRunner_GPS ), I can't find a
> (successful) way to get the result from the chip. From my view, I
> should cat the commands to ttySAC1 and then read it. But I get nothing
> exciting that way...

You should get either a ubx packet of type ACK-ACK or ACK-NACK
depending on whether the chip accepted your CFG-NAV packet.

Daniel Willmann
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