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[aprssig] APRS radios

Bob Bruninga bruninga at usna.edu
Sun May 25 14:16:50 UTC 2008


> I asked about bulletins yesterday.  Yep, that's 
> a message packet,  sure, well...maybe just almost, 
> it doesn't have a sequence number.   
> To fully implement the "message" types of packets, 
> you have to do a bunch of special bulletin processing.

Im not sure how much simpler it can be...
If it is a bulletin, sort it onto the bulletin page. If it has a message number, ack it.  I dont see how that can be called a bunch of special processing...

>  Then you have to think about third party packets...

Third party and Objects is where I think the spec overly complicated APRS.  It was so simple.  An object is NOT a special packet with its own formats.  It is simply a position report of an object name that is not a callsign.  So the name has to be in the packet, and not in the AX.25 header where the callsign is.

On receipt, all one was supposed to do was chop off the header, and then use what remained (which now contains a NAME instead of a call) as if it had been received on RF directly.  Just rearrange the name into a pseudo packet and then continue parsing like any other packet.

Same with 3rd party.  Simply strip off the header, and then drop it directly through the rest of the parser.  A simple one-line process.

So in that sense, I agree that the APRS spec is a monster in how it tediously attempts to document these things as separate enteties.  Again, it tries to make objects a completely different animal, when they are simply a position report with a NAME other than a callsign.  So follow-on authors tend to build object parsers, when in fact, an object should be treated identical to the position parser of all other packets.

In writing each one as a special thing, the spec hides the bigger picture which is really not that complex.

Bob, WB4APR





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