[aprssig] Re: APRS radios

[Curt, WE7U]

On Mon, 26 May 2008, Chris Kantarjiev wrote:

> Implementation issues aside (and that's a big leap), a core
> problem is that *there is no spec* that accurately describes
> the system, and there is certainly no sort of formal acceptance
> suite or criteria.
> 
> Beyond the basics, everyone has made it up as they went along,
> and the only documentation is code that may or may not be
> available in source.

The "spec" is more complete than you're describing, but you have to
know where to look for it, plus understand that it is still
evolving.  There certaily are things that are ambiguous yet and/or
incompletely described as well:

  http://info.aprs.net/index.php?title=Protocol


> I ran into the difficulty when I was writing code to parse
> on-the-air packets in perl! The "spec" on the tapr website
> is incomplete and out of date, but there is nothing better.
> I resorted to using bit tweezers on the packet stream from
> a local high-and-wide digi. 

The best start for a Perl decoder is the Perl code that Ian wrote
when he was editing the original spec.  It would need a few things
added to catch up the Addendum portions of the spec, but it's fairly
complete otherwise.

-- 
Curt, WE7U.				archer at eskimo dot com
http://www.eskimo.com/~archer
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