[aprssig] APRS bit I/O

Rich Mulvey aprs at mulveyfamily.com
Thu Jun 28 14:41:19 EDT 2007

'Scott Miller' wrote:
>>    For output, I would use something like:
> That's a little verbose.. I was thinking of a more compact, tagged hex
> format.

   I guess it depends on who you expect to be issuing the commands - if 
I'm sitting at a keyboard, I'd definately want to have something more 
human-readable.  If it's another device spitting out commands, then 
having a format using some sort of bit mask, etc, would be fine.

>>    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.

   Hmmmm, interesting.  According to 
http://www.maxim-ic.com/appnotes.cfm/appnote_number/187 , you're 
correct.  In practice, I have some long ( 100 yard ) 1-wire nets with > 
15 or so sensors in which I definitely get the ID's back in varying 
orders, using the DalSemi OneWireAPI libs.  Now you have me curious 
about the reason...

- Rich

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