[Gllug] Using a GPS receiver (Navman B10) with Linux

[John Winters]

I yielded to temptation a few days ago and bought a Navman B10 bluetooth
GPS receiver, having seen various postings on line reporting success
with it, and finding it could be had for less than 20 beer tokens.

Anyway, in traditional style, when it arrived I just plugged it in (to
charge it) and started fiddling.  In very short order I had it up and
running and gpsdrive reported that I was at home (I knew that anyway).

I then decided to set things up again a bit more methodically, since
when I have totally failed to get it to work.  Most components seem to
think that all is well, but gpsd just doesn't seem to recognise the
output.  Unfortunately I didn't keep notes the first time I did it so I
don't know what the magic incantation was which worked.

I get the following:

liberty:~# hcitool scan
Scanning ...
	00:0B:0D:18:EE:B8	NAVMAN GPS TWO
liberty:~# rfcomm connect /dev/rfcomm0 00:0B:0D:18:EE:B8
Connected /dev/rfcomm0 to 00:0B:0D:18:EE:B8 on channel 1
Press CTRL-C for hangup

At this point both my PC and the Navman seem to think they are connected
(the Navman indicates this by changing the flash rate of one of its LEDs).

However if I now invoke gpsd (with debugging turned on) it does lots of
probing to try to talk to the GPS unit and finally reports that it can't
make any sense of it.  I do however seem to have comms.  If I run:

hexdump -C /dev/rfcomm0

I get a steady flow of (rather repetitive) binary data, like this:

000050c0  e0 78 fe 80 f8 00 78 e0  00 78 e0 00 80 00 80 00
|.x....x..x......|
000050d0  80 00 80 80 78 1e f8 f8  f8 80 80 80 80 78 fe 00
|....x........x..|
000050e0  80 78 00 00 80 80 f8 00  f8 00 78 fe 80 80 78 fe
|.x........x...x.|
000050f0  78 fe 80 f8 f8 00 f8 00  78 e0 78 00 80 00 80 00
|x.......x.x.....|
00005100  f8 80 00 f8 80 78 1e 80  00 f8 80 80 78 e0 00 80
|.....x......x...|


I don't know enough about GPS data to know whether this is meaningful or
there is a synchronisation problem.  (Does it make any sense to talk
about BPS in a bluetooth context?)  The data don't change, but since I'm
sitting still I wouldn't really expect them to.

Anyone any experience of this things able to give me some pointers?

TIA,
John


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