[aprssig] Kenwood/Garmin adapter update

Scott Miller scott at opentrac.org
Mon Sep 8 10:22:31 CDT 2008

> Nice PCB Scott. For programming, there are sockets that can take the IC 
> package and allow you to program off the PCB. If you need me to hunt for 

Hard to do with a QFN... you've got to take it off the tape, drop it in 
with a vacuum pen, and then repackage it somehow.  Much easier to ship 
it to the contract manufacturer on the original tape, and then program 
it once it's on the board.  For this one, I'll probably machine a 
fixture out of Delrin and put pogo pins in it.  I just haven't had a 
chance to do that yet.

> one I can probably pull a few strings for you; let me know the package 
> specs. That would eliminate some of the soldering.

It's a 7mm 48QFN.  The sockets tend to be really expensive, though I did 
get a handful of different types at a surplus place in the Bay area for 
$5 each.

> Is this basically a USB to RS232 adapter without the PC? This is a great 
> idea and could be used in many other applications. I've been thinking 

Unfortunately, no.  The nuvi won't even work as a GPS once you hook it 
up to a USB host - it just becomes a dumb mass storage device to manage 
waypoints and files.  There's no USB-related firmware in this thing at 
all.  It just has to do a bunch of floating point math and some 
trigonometry to convert between the Garmin 9600 baud binary stream and NMEA.

I *do* have embedded host controller chips around here that could be 
used for some USB/serial applications.  BUT... you've got to know 
exactly how the USB device communicates (at least Garmin documents their 
interface) and you've also got to have power for the host, and probably 
power for the target device as well, since it's going to expect external 
power when it's connected to a USB host.  That rules out a simple 
in-line cable adapter like this project.


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