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

Olivier Migeot larrycow at gmail.com
Wed Jan 14 18:18:26 CET 2009

Hi ev'ryone,

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).

I did some quick tests, using my work phone as a reference (an HTC
Trinity with a Sirf chip) : when logging car trips, both tracks are
pretty close. Like a few meters. Far better than what I expected, at
least. But when logging pedestrian trips (and I do quite a few), the
Antaris starts to behave like ... a car. Every steep turn I took is
throughly rounded on the Neo-based log. So I guess the current setting
of our chip is "car". So I wonder : does anyone here know whether we
got "version 3.04 or higher" of the software?

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...

I guess I should shut down FSO's GPS handling first, but how? Is
stopping fso-gpsd enough? (I tried, but it didn't seem better)

Any insights, somebody? Thanks.


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