On 19/03/2011 20:07, Marc MERLIN wrote:
> On Sat, Mar 19, 2011 at 07:49:03PM +0100, Pascal Baerten wrote:
>> Marc,
>>
>> The 1-wire protocol has an unique discovery protocol where every slave
>> participate to enumeration sequence initiated by the master. this is the
>> search
>> algorithm <http://www.maxim-ic.com/app-notes/index.mvp/id/187>
>> A conditional search utilize the same method to discover only alarmed
>> devices. When le conditional search command is issued by the master, every
>> devices on the bus receive it but only thoses with alarm condition
>> participate. The participating devices are shown in the alarm directory.
>
> Got it, and I take it owfs automatically does 'alarmed only' searches on its
> own on 1sec interval or somesuch.
No. owfs does nothing on its own. It does 'alarmed only' searches when you
ask it to list the contents of an alarm/ directory.
>> You then simply get directory list of alarm folder; if devices are shown
>> there you know that some condition are met for those and you read their
>> input state.
>>
>> if you configure the slaves to trigger the alarm only on latch bit (instead
>> of sensed) you ensure that when accessing the device to reset the latch, you
>> neutralize the alarm condition until new pio change occurs.
>
> I found the set_alarm property in the docs for DS2408, but I'm a bit
> confused as to how you read alarms in owfs.
>
> There is no alarm subdir in /owfs or /owfs/uncached/
Is there a documentation about the exact layout of all owfs ?
For each sensor, the corresponding manpage list most of them (I think
I have to report the missing ones when I found them ;-) )
But the layout of the root (ie what is in bus.0 settings statistics
structure system uncached) is something I try to guess from what
I observe at home. If there is a reference documentation, I would
be pleased to know it.
> I do have a hub however, and I see alarm under /owfs/1F.F05005000000/aux/
> for instance, but most of my devices are listed in there too.
> Does that mean that alarm is somehow set for all my DS18[SB]20s, DS2408, but
> interestingly not DS2438 and DS2760.
If I understand correctly (I also have a hub), each DS2409 allows to have
two separate branches (main and aux) that can and must be scanned separately
from the global 1-wire network.
If you want to enumerate devices on a subbranch, devices on other branches
will not be involved. But if you want to scan on all your devices, you will
have to do it on all DS2409 branches.
Regards,
Vincent
> set_alarm in my DS2408 currently says '0', so I'm not sure why it shows up
> in the alarm subdir.
> I'll have to look closer to see what's up. Thanks for pointing me in the
> right direction.
>
> Marc
--
Vincent Danjean Adresse: Laboratoire d'Informatique de Grenoble
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