> Thank you for your answers!
>
> The problem with selective search is that I don't know if the device is still
> on a bus or not, so polling on ordinary search is more reliable for hardware
> failure detection.
I periodically scan the root directory and compare the result with the previous
scan. This allows us to detect the disappearance of devices on the bus and the
emergence of new ones.
> Second, alarm is set for sensed values, not for latches, so it is possible to
> miss some very short event.
Hmm..
------------------ man DS2406 ---------------------
set_alarm
read-write, unsigned integer (0-331)
A number consisting of three digits XYZ, where:
X
channel selection
0 neither
1 A only
2 B only
3 A or B
Y
source selection
0 undefined
>>> 1 latch <<<<
2 PIO
3 sensed
Z
polarity selection
0 low
1 high
--------------------8<------------------------
This will see an event that occurred between periods of polling.
>
> I know, 1-wire is not the fastest network on the Earth, but I'm trying my
> best :)
>
> PS.
>
> It seems it is not possible to set negative alarm values for DS18B20
> temperature sensors. Or it is a bug in owhttp interface?
>
>
> Best Regards,
>
> Ivan, PhD
>
>
>
>
> On Tue, Mar 27, 2012 at 12:13 AM, Serg Oskin <[email protected]
> <mailto:[email protected]>> wrote:
>
> Try to use the alarm-directory.
>
> # Setup
> foreach 12.*
> openeach
> writevalue_to_set_alarm
> closeeach
> end foreach
>
> # Main loop
> foreach uncached/alarm
> openeach
> readvalue
> reset_alarm
> closeeach
> end loop
>
> --
> Serg.
>
> > Greetings to all,
> >
> > I am implementing a system which need to poll sensors (mainly DS2406
> and DS2408) nearly every second. Of course I use uncached values of sensors
> to get the most recent data. I have about 15-20 sensors to poll.
> >
> > I see three options:
> >
> > First:
> > loop:
> > openfile("12.XXXXXXXX/latch.A");
> > readvalue;
> > closefile;
> > end loop.
> >
> > The most obvious one, but open/close file is rather costly operation.
> >
> > Second:
> > openfile("12.XXXXXXXX/latch.A");
> > loop:
> > readvalue;
> > goto_first_line;
> > end loop;
> > closefile;
> >
> > This is better, but is there some chance, that value will be cached
> somewhere inside OS?
> >
> > Third:
> > give up on owfs and use owhttpd and make tcp connections to read files.
> >
> > I think this is a heaviest one, but crossplatform, so can be used on
> windows. Can owhttpd have about 20 concurrent connections in a second?
> >
> >
> > What strategy to choose? Thank you for any help in advance.
> >
> >
> > Best Regards,
> >
> > Ivan, PhD
> >
> >
> >
> >
> >
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