[aprssig] Nuvi 350 still on sale thru the end of Aug 09 WEB Only

[Stephen H. Smith]

Michael Hatzakis Jr MD wrote:
>
> I am considering buying one of these Garmin 350's to power APRS in a 
> laptop and other GPS functions, is this a standard serial/USB 
> compatible signal?
>
NO!   By itself, it won't do ANYTHING!    The Nuvi has a USB interface, 
but it doesn't, by default, provide live data out in any format.   The 
normal USB interface is intended primarily for uploading software 
patches, updated maps and user-created points-of-interest lists TO the 
device. Live GPS position data DOES NOT normally come out of the device. 

> How about for an Icom IC91D?  What will it take to make it compatible 
> with serial/USB, and for the IC91AD?  
>
>  
>
> ideas for a technically savvy person?
>
>  
>
> Michael  K3MH
>
>  
>
> ------------------------------------------------------------------------



Certain Nuvi models, including the 350, have a built-in 
firmware/hardware feature called FMI (Fleet Management Interface).  When 
the conductors of the USB port are pulled up or down with suitable value 
resistors inside a special cable, the USB interface "automagically" 
transforms itself into a classic serial interface instead.  This enables 
real-time download of GPS data and upload of waypoint data for plotting 
objects on the screen.  

FMI also offers a messaging interface that uses the soft keyboard 
display normally used for entering addresses to compose text messages 
for transmission.  Unfortunately all these goodies are in a proprietary 
Garmin protocol, intended for developers of custom commercial 
AVL/messaging systems.  Some details are here:

     <http://www8.garmin.com/solutions/pnd/>

Some of the Garmin units that support this hidden mode are listed here:

    <http://www8.garmin.com/solutions/pnd/supportedproducts.jsp>



 From the standpoint of APRS users, the only two devices that can 
directly exploit the Fleet Management Interface are:  

o     The Argent Data "G-Trans" cable for the Kenwood APRS radios.  This 
device has a mini-USB plug on one end (to go into the Garmin), and a 
2.5mm stereo miniplug on the other (to go into the Kenwoods' dedicated 
GPS serial port).   This cable, with an embedded microcontroller in a 
"goiter" in the middle of the cable,  translates Garmin FMI live 
position data from the Nuvi to serial standard 4800 baud NMEA ASCII for 
use by the Kenwoods and other NMEA-using devices.  

The Kenwood APRS radios are capable of translating incoming posits 
received from other station into NMEA $GPWPL waypoint strings which can 
be sent back to many display GPS devices that accept and plot waypoint 
data. This data is fed OUT of the dedicated GPS port on the Kenwood 
radios,  BACK to the GPS on the other half of the serial cable bringing 
GPS data TO the radio. 

If this feaure is enabled in the Kenwood radio, the G-Trans cable will 
convert $GPWPL waypoints back to Garmin FMI format for display on the 
Nuvi 350's maps.  Details on this cable for the Kenwood radios here:

     
<https://www.argentdata.com/catalog/product_info.php?cPath=28&products_id=113>

The G-Trans cable is also available with a standard DB9 serial plug on 
the end rather than the 2.5mm stereo miniplug used by Kenwoods.  (The 
GPS data OUT should be usable by ANY device (tracker, laptop, etc) that 
accepts normal RS-232 4800 baud NMEA 0183 GPS data.   The waypoint data 
IN would depend on the capabilities of the attached device.)  Details on 
the alternate G-Trans cable here:

    
<https://www.argentdata.com/catalog/product_info.php?cPath=28&products_id=114>


o     The Argent Data Tracker 2 (tracker & send/receive TNC) which can 
use the Nuvi 350 as a GPS source for the tracker, and the screen as an 
APRS mapping display and messaging terminal.    [The program code for 
dealing with the FMI protocols are built into the T2's firmware.]  The 
T2 has to be connected to the Garmin with the DB9 version of the G-Trans 
cable.

 

Note that these are open-sourced devices, so the program code for 
dealing with FMI is visible and can be used as a starting point for 
developing similar capabilities in other software.

------------------------------------------------------------------------



--

Stephen H. Smith    wa8lmf (at) aol.com
EchoLink Node:      WA8LMF  or 14400    [Think bottom of the 2M band]
Skype:        WA8LMF
Home Page:          http://wa8lmf.net

JavAPRS Filter Port 14580 Guide
  http://wa8lmf.net/aprs/JAVaprsFilters.htm

"APRS 101"  Explanation of APRS Path Selection & Digipeating
  http://wa8lmf.net/DigiPaths

Updated "Rev H" APRS            http://wa8lmf.net/aprs
Symbols Set for UI-View,
UIpoint and APRSplus:


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