On Mon, Mar 13, 2006 at 11:05:04PM +0100, Jan Kandziora ([EMAIL PROTECTED])
wrote:
> Am Montag, 13. März 2006 21:56 schrieb Evgeniy Polyakov:
> > > > 1. w1 supports on-demans searching in the following way:
> > > > search is performed on $w1_timeout interval basis, which is provided as
> > > > module parameter. By manipulating w1_master_search sysfs file one can
> > > > trigger to search or not on next $w1_timeout interval.
> > >
> > > Ok. That would mean I could set $w1_timeout to e.g. 0s and disable it by
> > > default. Whenever I want to search, I'll enable the sysfs file, then
> > > disable again immediately. Right?
> >
> > $w1_timeout should be set to more meaningful alue, since it is also
> > timeout used for deice state check and possibility to sleep for suspend.
> > Just setting w1_master_search to 0 is enough to stop repeated searches.
> >
> Hm. I'm concerned about bus load if all devices on the bus are scanned
> isochronously.
>
> I design a semiautomatic vending machine. It's planned so far with 50..200
> onewire chips on one bus. I need a time slice of ~250ms in my application,
> but only for the few chips which are "active" in a certain, user-application
> controlled process.
>
> As adressing and such needs ~50Bit, 100Bit per chip read/write cycle is my
> "thumb value" for any operation. At 16kBaud, that would limit isochronous
> operation to 120..140 operations per second. Which on the other hand means,
> 30..35 chips are the maximum for isochronous operation and 250ms time slice.
>
> I don't know how overdrive speed improves this, but overdrive speed certainly
> would limit the cable length, too.
>
>
>
> For such applications as mine, it would be better to have more control over
> which chips are "interesting" in some situation, and should be updated more
> often and which are not. Maybe you (or we) can put some "rating" on each
> chip, and an interface for the application program.
>
>
> Or did I misunderstood your wohle concept?
Repeated search is needed for authentification cases and ibuttons.
It also helps to detect bad lines.
Current design allows to setup w1_master_search per bus master device,
so in case of auth checks and big number of devices it would be better
to setup two masters for each kind of usage case.
> Kind regards
>
> Jan Kandziora
> --
> MCSE: Minesweeper Consultant and Solitaire Expert
--
Evgeniy Polyakov
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