Am 23.09.2015 um 14:35 schrieb Alex R. Gibbs:
>
> We have dozens of DS18B20 temperature sensors at 3 telescopes. I'd like to
> poll
> them and cache the results so that other programs can retrieve the latest
> temperatures with less than 50ms delay.
>
So basically, you want the other programs to access the cache *only* and never
trigger a conversion themselves because that may take while. That's something
you
cannot enforce with owfs, you can only ensure it by taking additional
precautions.
1. Power all sensors. That's required because we want to use simultaneous
conversion
in the next step. Why do you want that? Because you wrote "dozens of sensors"
and
conversion for dozens of sensors would take up dozens of seconds if you do
single
conversions.
2. Trigger a simultaneous temperature conversion every n seconds (with n being
smaller than the cache timeout for temperature). You do that by writing "1" to
/simultaneous/temperature. Use a simple script like this:
#!/bin/sh
while : ; do owwrite -s localhost:4304 /simultaneous/temperature/ 1 ; sleep 1 ;
done
Don't forget to wait a second so the first conversion result is ready.
3. Read the cached values in the sensor directories as often as you like. They
should
never trigger a conversion by themselves because the script from step 2 has
already done
that.
Kind regards
Jan
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