Am Mittwoch, 31. Mai 2006 23:09 schrieb Alfille, Paul H.,M.D.:
> Correct.
>
> I don't know how large your network is, but there are issues with the
> DS2409.
>
There will be ~80..150 chips for each machine, so triggering the search
algorithm for the entire network is a great cost.
> Basically, we trigger "branch selection" in the most efficient manner, but
> owfs is designed to be multiuser (or at least multiprocessing) which means
> another thread may have selected away from the DS2409. This is no problem
> for reading or writing, but the datasheet says some "presence alarms" may
> be lost. The alarms state of chips on the branch should be preserved.
>
That should be no problem, as we use a single application -- a hardware
control daemon, which does the whole timing etc. -- to control the onewire
network.
> We can work on enhancing the full function, but I'd do some extensive
> testing to make sure you don't get locked out.
>
Hm. At least from my point of view, if it's only a problem of concurrent
access, it isn't urgent.
> The DS2409 certainly partitions the network, but it adds its own
> inefficiencies. Selecting any branch involves considerable communication.
>
Yes, but searching is even more inefficient. In addition, I need to put the
keylock in a different branch anyway, just to get its physical position from
the ID of the attached DS2409 -- the keylock itself is just a plug to the
onewire, which could be located anywhere.
> If you only want to reduce the number of chips that need to be scanned, and
> you have an appropriate network design, you can simply add more
> bus-masters. owfs can address them individually or in a unified manner, and
> searches on them are multithreaded and concurrent.
>
I thought about that, too. But that means to connect a lot of busmasters to
the machine (about 5..10), and to use a lot of additional cabling. As the
machines should be put together at the installation side by (more or) less
trained staff, straightforward cabling is possibly the most easiest to
explain.
Kind regards
Jan
--
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completely unintentional side effect. -- Linus Torvalds
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