[aprssig] aprssig Digest, Vol 105, Issue 13

[Alex Carver]

> Message: 3

> Date: Sun, 17 Mar 2013 14:15:24 -0400
> From: Robert Bruninga <bruninga at usna.edu>
> To: aprssig at tapr.org
> Subject: [aprssig] APRStt works!
> Message-ID: <a4dfdc828440c3c490b13ea5bc2172a1 at mail.gmail.com>
> Content-Type: text/plain; charset="windows-1252"
> 
> We used APRStt successfully yesterday to allow anyone with any HT to report
> their positions along our Marathon by entering only the DTMF code ?B1MM*??
> followed by their callsign from DTMF memory.  The MM number was converted
> by a lookup table to the exact position of the mile mark.  Further, anyone
> could report themselves anywere in the 10 mile grid to the nearest 600? or
> so using the DTMF format ?B2XXYY*?
> 
> 
> 
> We think that has great potential to expand the use of APRS at events,
> since everyone in the club could input data, not just the 10% that had APRS
> capability.
> 
> 
> 
> See the web page:
> 
> http://aprs.org/aprstt.html
> 
> 
> 
> More to come when Byonics eventually decides to make these DTMF adapters
> available.  Right now, only 3 of us have alpha models for experimentation.
> But be thiking of how you can use EVERYONE in  your club at your next event
> to enter data.  For example, how we report Boy Scout troop scores at our
> camporees:  http://aprs.org/aprsevent.html
> 
> 
> 
> Our local Repeater owner also said he would be happy to put an APRStt
> decoder on the repeater input so that non-APRS mobiles in the area could
> easily be seen on APRS too?


Bob, I see a bug in your callsign encoding.  You use a single number key to encode a number but you use a number and then a letter to encode the letters.  The problem comes when you perhaps lose one of the letter keys (interference, bad key, etc.) which is then interpreted as a straight number.  Perhaps you should amend your format such that numbers are prefixed with 0.  This keeps the 2-symbol-per-character encoding consistent and also provides a flag for signalling a numeric.

I know that uses up a little bit of  airtime but it isn't much when talking about the callsign and adds a bit of error checking.