Am Dienstag, 5. Dezember 2006 14:31 schrieb Jan Kandziora:
> Dear all,
>
> as scanning the onewire using the "SEARCH ROM" command is still expensive,
> I thought about different functions for detecting "plug-in" and "pull"
> events for a lock in my program.
>
Another idea: Is the "Read ROM" command implemented in owfs? Using the
DS2482-800 this could be an easy way to connect up to 8 onewire locks to a PC
and avoid scanning.
As far as I understood, it is possible to generate a reset pulse on a sub-bus
of a DS2409 only -- in conjunction with a directly following "Read ROM"
command, scanning could be avoided there, too. And this would enable
connecting an unlimited number of locks placed anywhere on the bus and
identifed through the DS2409's ID.
I have made a schematic and PCB for such a DS2409 driven lock already, but the
idea of continously scanning the bus is still making me nervous.
It takes 64 I²C bytes to scan for a single key but only 9 I²C bytes to read
the key's ROM. The DS2482<->I²C host interface seems to be the biggest
bottleneck as the I²C host buffers only one command/reply at a time, and
therefore, each I²C byte triggers either an interrupt or busy loop.
So reducing I²C traffic could greatly improve overall system performance.
Any musings about that?
Kind regards
Jan
--
Ein Rechner tut genau das, was der erfahrenste Nutzer auf dem System will.
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