What you do here is that you initiate a simultaneous read, and force two
simple reads after as well. You should initiate the simultaneous read, wait
1-2 seconds, and read the cached values.
Attila
On Thu, Oct 10, 2013 at 1:11 PM, Håkan Elmqvist <hak...@smeden.org> wrote:
> In order to explore simultaneous temperature readings I have set up two
> DS1820 with VDD connected to +5V and executed the commands below. As can
> be seen from the resulting output writing to
> /ow/simultaneous/temperature takes only 40 ms instead of the expected
> 0.7 s and the two temperature readings take a total of 1.4 s.
> What am I doing wrongly?
> I am using owfs-2.9p1 on an AMD Athlon(tm) 7450 Dual-Core Processor
> running Ubuntu 12.04.3 LTS.
> Thanks in advance for any tip.
> Håkan
>
> root@hemx:/# pkill owfs; /opt/owfs/bin/owfs -u --allow_other /ow; ls /ow;
> \
> cat /ow/10.*/type; echo; cat /ow/10.*/errata/die; echo; cat
> /ow/10.*/power;echo; \
> time echo 1 >/ow/simultaneous/temperature; \
> time cat /ow/uncached/10.*/temperature;
> DEFAULT: ow_usb_msg.c:(295) Opened USB DS9490 bus master at 4:4.
> DEFAULT: ow_usb_cycle.c:(191) Set DS9490 4:4 unique id to 81 66 09 28 00
> 00 00 44
> 10.4E272C020800 10.C11E2C020800 81.660928000000 alarm bus.0
> settings simultaneous statistics structure system uncached
> DS18S20DS18S20
> C2C2
> 11
>
> real 0m0.041s
> user 0m0.000s
> sys 0m0.000s
> 22.25 22.25
> real 0m1.388s
> user 0m0.000s
> sys 0m0.000s
> root@hemx:/#
>
> --
> Håkan Elmqvist
> Sunnerdahlsv 7
> 167 62 Bromma
> Telefon: +46 (8) 80 18 81, +46 (704) 56 74 81, +46 (176) 84 077
> epost: hak...@smeden.org
>
>
>
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