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
--
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Home page: http://marc.merlins.org/
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