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[aprssig] APRS bit I/O

'Scott Miller' scott at opentrac.org
Thu Jun 28 17:55:58 UTC 2007


>    For output, I would use something like:
> 
>    SWITCH ID,BIT,STATE

That's a little verbose.. I was thinking of a more compact, tagged hex
format.


>    You can't just assume that if you have multiple devices, you'll 
> always get their addresses back in the same order
> when you do a 1-wire ROM SEARCH command.  It's completely arbitrary - 
> especially if you have other 1-wire

The SEARCH ROM command is completely deterministic.  It has nothing to do
with how fast they respond.  Granted, if you add another device you're
likely to screw up the ordering.

Exactly WHAT order they show up in depends on how you implement the
algorithm.  The T2 always sends a zero first when it encounters a conflict.
It could just as easily start with a one and still find all the devices, but
in reverse order.  I'd paste the code here, but it's an ugly mix of C and
assembly.

Scott
N1VG







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