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[aprssig] Kenwood/Garmin adapter update

Scott Miller scott at opentrac.org
Sun Sep 7 23:49:11 UTC 2008

I've got the first couple of prototypes of my Garmin <> NMEA converter 
board build and running - beta testing will be starting soon.  This 
board is intended to work with the nuvi and StreetPilot models that have 
a mini-B USB connector (and support fleet management mode.)  Here's a 
picture of my TH-D7A hooked up to a nuvi 350:


So far only the nuvi 350 works right for waypoint display, but I think 
Garmin's going to have a solution for that soon.  Here's another shot of 
the converter circuit, this one with a DB9:


It'll probably get overmolded directly into the cable eventually, but 
for now it's just encapsulated in adhesive-lined heat shrink tubing. 
Here's the PCB itself:


Afraid I only had my phone camera handy when I took that, so the quality 
is bad.  The whole thing is about 2mm thick.  I probably could have made 
it a little narrower, but I got tired of playing with the routing.  It's 
got a 20 MHz HCS08 processor on it, a clock crystal, ESD protection, and 
an RS-232 transceiver.  It's all powered by the nuvi (but not when the 
nuvi is on battery power).

I've only got a few prototypes, and I've already got beta testers lined 
up.  I'm afraid I can't build any more until I get more USB cables 
(they're non-standard 5-conductor cables with a custom right angle 
overmold, and the factory is just getting started on them) and soldering 
a 7mm, 48-contact QFN chip by hand is exceedingly tedious.  I also 
haven't built a programming fixture yet, so loading the firmware 
requires soldering wires to test pads and then removing them again when 
it's done.

But it works!  Plug it in to the nuvi and it starts spitting out GPGGA 
and GPRMC sentences.  It'll take GPWPL and PKWDWPL (D710) waypoint 
inputs, and in the case of the PKWDWPL format it'll pick an appropriate 
symbol as well.

I'm planning on a retail price of $48 for the converter cable.  I'll let 
everyone know when it's available.


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