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
