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[aprssig] APRS and Garmin Nuvi

Brian Webster bwebster at wirelessmapping.com
Fri Feb 1 04:46:52 UTC 2008


Scott,
	This is awesome news!!! We may just be ushering in the next phase of mobile
APRS. The text messaging would be a neat feature and the display of this
looks great. Please keep us posted on your findings. This will certainly
make me purchase a Nuvi and OT2.



Thank You,
Brian N2KGC

-----Original Message-----
From: aprssig-bounces at lists.tapr.org
[mailto:aprssig-bounces at lists.tapr.org]On Behalf Of Scott Miller
Sent: Thursday, January 31, 2008 11:01 PM
To: TAPR APRS Mailing List
Subject: [aprssig] APRS and Garmin Nuvi


I discovered something interesting today.  Here I've been telling people
all along that the newer USB-only Garmin receivers like the Nuvi are
worthless for APRS.  Turns out I was wrong.

When I heard about Garmin's fleet management interface, I decided it'd
be worth checking out.  It needs a special cable, though - for the Nuvi
350 I picked up, it's Garmin p/n 010-10813-00.  By the looks of it, it's
probably just got a level converter inside, but I'm not sure.
Apparently there's a serial interface of some sort that can share the
USB connector.

The fleet management protocol looked suspiciously like a subset of
Garmin's regular binary serial protocol, so (once I figured out the
cable pinouts and soldered on a DB9) I fired up the test program I'd
written, and sure enough, it spit out a list of supported protocols.

I plugged it straight into a stock Tracker2 and the activity light
started blinking green, showing a good fix.  I piped in some recorded
APRS traffic and the map screen started showing APRS stations.  Here are
some pictures I took (haven't tried the screen capture program yet):

Map screen (2D mode): http://n1vg.net/images/nuvi-map.jpg
Waypoint list: http://n1vg.net/images/nuvi-list.jpg
Station detail: http://n1vg.net/images/nuvi-detail.jpg

It's not perfect - the waypoint set is different, for one.  You can see
that all of the cars are now up on lifts with the hood up!  The digis do
show up as antenna towers, at least, and the houses are there.  I'll
have to find out if it'll take custom symbols.  Also, it seems to have
some quirks about showing waypoints at different zoom levels.

The Nuvi 350 has a USB port on the side and another one on the clip-on
base, so you can power it and plug it in to the tracker at the same
time.  When I find out how the serial interface adapter works, I'll see
if I can power it from the tracker, or maybe vice versa.  I'll also see
about a cheaper substitute for the cable - this one cost me $30 after
shipping.  It probably wouldn't be hard to build an equivalent circuit
into a DB9 shell.

The bad news is that the Tracker2 (at least the OT2m version) is totally
sold out right now.  My only two spares are going out for CE EMC
certification shortly.  The factory producing the boards is snowed in
right now and hasn't even been able to get the parts for the next batch
- DHL's had them sitting at the depot for days.  It'll probably be the
end of February before I have any more.  The T2-135 (for the Alinco
DR-135) is shipping, albeit slowly due to limited production capability
here.  (The Tracker2 page has moved to
http://www.argentdata.com/products/tracker2.html if you're looking for
more information.)

Hopefully by the time the boards come in I'll have figured out all of
the Nuvi's quirks and dealt with them.  I also hope to make some use of
the fleet management interface for some new features.  Most importantly
- it does text messaging.

Scott
N1VG


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