[Gta04-owner] GPS support in Replicant 4.2

Lukas Maerdian luk at slyon.de
Fri Apr 25 15:04:50 CEST 2014


Hi Paul,

2014-04-24 23:05 GMT+02:00 Paul Kocialkowski <contact at paulk.fr>:
> I'm very happy to announce that GPS support is now complete on the
> "upstream" Replicant 4.2 tree!
>
> The performances of the chip are quite outstanding too, and getting a
> fix is really fast with the internal antenna outdoors. It is even better
> with an external antenna. Precision is also real good: it can tell which
> side of the street I'm standing on!
>
> Here is a photo of my device with a location fix, using the OsmAnd
> application, available on F-Droid:
> http://download.paulk.fr/replicant/gta04/gps.jpg
>
> Regarding the implementation, it's already pushed on the gta04 device
> repository over at
> https://gitorious.org/replicant/device_goldelico_gta04 (branch
> replicant-4.2).
> While I wrote the GPS module from scratch (and licensed it under the GNU
> GPLv3+, as well as the rest of the repository), reading the Freerunner's
> GPS implementation was very helpful too.

That's great! Today I've imported some of your work also in the
Goldelico tree, and GPS is working fine (quick fix and nice accuracy).
In combination with the working WiFi, I was also able to use the
"MozStumber" app, to track WiFi cells and upload them to the Mozilla
Location Service :)

> Note that the serial is hanging when closing it. The close call takes up
> to ~5 seconds and is apparently waiting for that to happen:
> [ 5124.375305] GPS down
> [ 5124.382904] GPS up
> [ 5124.408477] GPS SET to 1
> [ 5124.411834] GPS idle
>
> Is there something I'm doing wrong? The relevant piece of code is at:
> https://gitorious.org/replicant/device_goldelico_gta04/source/6361460615e5cd8ddfe63c2daa378446d56ee128:gps/gta04_gps.c#L460
>
> Note that this isn't a problem at all, it just introduces a small delay
> when closing the application and opening it back in less than 5 seconds.

Hmm... I'm not sure (didn't read the code). But maybe it has something
to do with the 0-1-0 pulsing of the GPS chip, which is done in the
kernel driver (You should also see some "!!!!!!!!!!!!!!" in dmesg,
because of that). Here is a blog entry by Neal Brown about that GPS
driver, maybe it can shed some light:
http://neil.brown.name/blog/20120724060722

BR,
  Lukas


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