Patryk is right. The master initiates all communication (except perhaps for
a presence pulse when first connected).
That means that polling has done at some stage of the system.
You could have your program poll, or create a polling process and transmit
data from that. There are also some bus masters (the OWSERVER-ENET from EDS
comes to mind) that have polling incorporated with xml output. Since each
type of slave has unique properties and protocols, the polling routine has
to know the specific slave -- generally they are aware of the temperature
chips and some of the humidity sensors, depending on the target audience.
The w1 kernel subsystem also can poll, again mostly temperature chips.
OWFS is purely "pull" rather than "push" -- that was a design decision. It
allows nearly zero CPU consumption when not in use, and matches the 1-wire
actual architecture. It also allows a far broader support for the spectrum
of 1-wire slaves.
More task-specific programs do have polling integrated. E.g. OWW (one-wire
weather).
I don't know if this was insightful enough -- that's a stiff hurdle.
By the way, your domogik project looks interesting, though relatively
early. Can you tell us your eventual vision?
Paul Alfille
On Fri, Jul 6, 2012 at 6:41 AM, p4trykx <p4tr...@gmail.com> wrote:
> W dniu 06.07.2012 o 10:32 Romain Bourdy <rom...@bourdy.eu> pisze:
>
> > My question today is, is there any way to be notified of values
> > changes of a 1-wire sensor instead of polling at regular interval ?
> > Some of us use low resolution and would prefer a PUSH rather than PULL
> > approach in getting the values ( Think Message queuing / subscribe ).
> > Is there any way to achieve this with the actual OWFS ? Does hack
> > exists with the actual owfs python binding to workaround this ?
>
> If you mean that a sensor would send data when there is a change in temp
> or input state. It's not possible. Only 1-wire master can initiate
> communication.
> Lately there was discussion that some 1-wire/iButton slaves can do that
> but it's rather uncertain and limited to those few chips if it even works.
> So generally most popular DS18b20 has to be polled.
>
>
>
>
>
>
> --
> Patryk
>
>
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