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[aprssig] Nuvi messaging

Scott Miller scott at opentrac.org
Sat Feb 2 03:30:36 UTC 2008

I think you found the developer's kit, but to clarify... the Garmin 
receivers listed on that page support FMI, which is a protocol (based on 
the regular Garmin binary protocol) that allows a connected device to do 
things like send and receive text messages, enter lists of stops, and 
get an ETA for the next stop.

Tying it in with APRS is what the Tracker2 does.  The T2 already had 
support for the Garmin protocol, and could create waypoints - like the 
D7/D700/D710, but with more features.  And since it already did 
messaging, tying the Garmin stuff together with the messaging isn't all 
that hard.  I'm working on the outbound messaging stuff now.

Getting the Nuvi into FMI mode requires a specific serial command.  I 
haven't added that to the T2 code yet, but I intend to make it an 
option, since it changes the menu layout, and it stays that way until 
disabled by another serial command.

I'll place an order for some of the interface cables.  I can't really 
beat their retail price in small quantities, but at least I can ship a 
cable for under $10.  I should have them in before the next batch of 
OT2m's (the standalone version of the T2) gets here.


Steve Noskowicz wrote:
>    Slow down just a bit, please.  Some brief background is in order here.
>     I'm having difficulty understanding the tie-in between this fleet
> management "Messaging" and APRS.  Is the Nuvi simply acting as a display when
> presented with data on the USB, as well as the inverse.
>    It'll probably be obvious after you explain, but why does a GPS have/need
> messaging.  It's not sinking in.
>    What "puts" in into this mode, something sent *to* the Nuvi, or an entry on
> the Nuvi screen/kbd?
>    For $21 there can't be much more than resistors, at most, in that cable.
>    Looks like my 750 is a candidate.

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