openmoko at mazikeen.demon.co.uk
Mon Jul 7 16:37:08 CEST 2008
On Monday 07 July 2008, Kai Römer wrote:
> Hi Al,
> If you need testers, please contact me. I have several gta02v5
> available and can do tests in Germany Munich.
First stab uses the example perl functions from ublox for generating the
aid-ini data, replacing their hardcoded x,y,z with values for my location.
The copyright notice on the example code says you can't do anything with it
without permission so I can't give you the script, but I can tell you how to
reproduce it ;-)
Get the AssistNow online client application note from:
Create a new script aid-ini.pl and start with:
Go to section B - Sample Server implementation and append subroutines
clientdata_prepare and ubx_checksum to aid-ini.pl
You need to replace the $posx, $posy and $posz values in clientdata_prepare
with some that match your location. These are ECEF coordinated in m. There's
an explanation of the calculation method in:
Alternatively you can use the attached spreadsheet if it survives the list.
Just replace the lat and lon with values for your location.
You probably want to change the time accuracy to reflect the accuracy of the
Freerunner clock, and possibly the accuracy of your location estimate.
Now copy the script to somewhere suitable on the Freerunner and make it
executable. I'm using /usr/local/bin. You need to install perl if you don't
have it already:
opkg install perl
Switch on the GPS then run the script:
/usr/local/bin/aid-ini.pl > /dev/ttySAC1
If you cat /dev/ttySAC1 you should be able to see it using the current time
according to your Freerunner. TangoGPS makes it easier to see what it's
doing. In the only test I've managed so far it got a fix with a poor view of
the sky, while my Garmin Geko was still struggling to see 3 sats. It wasn't
quick, but it was better than the Garmin. It would be interesting if you
could try 2 units side by side, one with aid-ini and one without, to see if
it really makes a difference or if I was just lucky. I'll try to get some
more testing in, but the weather isn't good here, and I don't want to get my
new toy wet ;-)
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