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.
If the host thinks a certain key -- which was detected before by usual
scanning -- is plugged in a lock, it just has to check if this single onewire
id is still on the bus. I implemented this by checking e.g.
"bus.0/uncached/01.1234567890/present".
Is this the right way to trigger a "MATCH ROM" instead of "SEARCH ROM"? I'm a
little unsure as the "uncached" is still needed. Second, the DS2401 datasheet
states the following:
Match ROM [55h] / Skip ROM [CCh]
The complete 1-Wire protocol for all Dallas Semiconductor iButtons contains a
Match ROM and a Skip ROM command. (See the Book of DS19xx iButton Standards.)
Since the DS2401 contains only the 64-bit ROM with no additional data fields,
the Match ROM and Skip ROM are not applicable and will cause no further
activity on the 1-Wire bus if executed. The DS2401 does not interfere with
other 1-Wire parts on a multidrop bus that do respond to a Match ROM or Skip
ROM (for example, a DS2401 and DS1994 on the same bus).
Searching through the source haven't enlighted me much about this, too.
Kind regards
Jan
--
...very few phenomena can pull someone out of Deep Hack Mode, with two
noted exceptions: being struck by lightning, or worse, your *computer*
being struck by lightning.
-- Matt Welsh
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