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.
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.
Pascal
2011/3/19 Roberto Spadim <robe...@spadim.com.br>
> check ds1820 datasheet it´s a good source of information
> http://datasheets.maxim-ic.com/en/ds/DS18S20.pdf
>
> 2011/3/19 Marc MERLIN <marc_n...@merlins.org>:
> > On Sat, Mar 19, 2011 at 08:38:58AM +0100, Pascal Baerten wrote:
> >> Hi Marc,
> >> The protocol require that the master always initiate the communication.
> so
> >> polling is unavoidable.
> >> However the functinality you're wondering exist; you may reduce bus
> traffic
> >> by using alarm function:
> >>
> >> basically you configure the slave to respond to conditionnal search only
> >> when a change occurred on its inputs.
> >> on ds2408 use the set_alarm property to configure conditional behaviour.
> (
> >> http://owfs.org/index.php?page=ds2408) then iteratively look for
> alarmed
> >> slaves by enumerating devices of alarm directory and read bit state only
> on
> >> theses alarmed devices.
> >
> > So, how does the master keep track of who triggered their alarm?
> > Is it somehow quicker for the master to poll every device just for the
> alarm
> > bit and it already does so every second or so, or in the case of alarm
> are
> > the slaves able to send that bit?
> >
> >> while this polling does not seems effective when few slaves are
> monitored on
> >> the bus, this become really interesting when many have to be monitored.
> you
> >> are able to poll 10 time per second as many slave as the bus may hold.
> >>
> >> Adding the use of simultaneous property for temperature aquisition, and
> you
> >> never lock the bus for duration of a conversion. even ds18?20 temp
> sensors
> >> use alarm function to appears in alarm directory (after a conversion
> >> command) if temp goes outside given limits.
> >
> > That's great to know, thank you.
> >
> > Marc
> > --
> > "A mouse is a device used to point at the xterm you want to type in" -
> A.S.R.
> > Microsoft is to operating systems & security ....
> > .... what McDonalds is to gourmet
> cooking
> > Home page: http://marc.merlins.org/
> >
> >
> ------------------------------------------------------------------------------
> > Colocation vs. Managed Hosting
> > A question and answer guide to determining the best fit
> > for your organization - today and in the future.
> > http://p.sf.net/sfu/internap-sfd2d
> > _______________________________________________
> > Owfs-developers mailing list
> > Owfs-developers@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/owfs-developers
> >
> >
>
>
>
> --
> Roberto Spadim
> Spadim Technology / SPAEmpresarial
>
>
> ------------------------------------------------------------------------------
> Colocation vs. Managed Hosting
> A question and answer guide to determining the best fit
> for your organization - today and in the future.
> http://p.sf.net/sfu/internap-sfd2d
> _______________________________________________
> Owfs-developers mailing list
> Owfs-developers@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/owfs-developers
>
--
Pascal
www.brain4home.eu
to subscribe, send a mail to <list-subscr...@brain4home.eu>
------------------------------------------------------------------------------
Colocation vs. Managed Hosting
A question and answer guide to determining the best fit
for your organization - today and in the future.
http://p.sf.net/sfu/internap-sfd2d
_______________________________________________
Owfs-developers mailing list
Owfs-developers@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/owfs-developers
