Re: [Owfs-developers] How to Use Simultaneous

zeitvertreib . wissing Fri, 13 Mar 2020 09:07:07 -0700

Hello Jan,

I'm sorry, you are right.

I do not use bash commands, I do read and write operations from a Python3 program. I do it step by step, as I'm not used to Python.

I had a version with uncached, but there was another program error and I forgot adjusting the file path.

PATH = "/mnt/1wire/bus.0/"

initiation of conversion:

while True: # Hauptprogramm
t1 = time()
fw = open(PATH + "simultaneous" + "/temperature", "w")
fw.write("1")
fw.close()

reading values:

for i in tempList:
deviceFile = PATH + "uncached/" + temps[i] + "/latesttemp"
f = open(deviceFile, "r")
tempBuffer = float(f.read())
f.close()
if tempBuffer != 85.0:
tempw[i] = tempBuffer
print(temps[i], tempw[i])
break
t2 = time()
print(t2 - t1)

However, now I wonder about very short conversion times, shorter than 700 ms a single 12bit conversion shoul take.

1st run:

28.0A651B2D1901 26.625
28.0A35192D1901 22.875
28.0CB479A20003 21.75
28.8BE0182D1901 28.875
28.80A7112D1901 29.5
28.629B082D1901 22.75
28.953D062D1901 22.875
28.613079A20003 22.25
28.CF52142D1901 22.8125

1.3515775203704834 sec

following runs

>>> %Run TempLesen.py
28.0A651B2D1901 22.9375
28.0A35192D1901 22.9375
28.0CB479A20003 21.75
28.8BE0182D1901 23.125
28.80A7112D1901 23.125
28.629B082D1901 22.75
28.953D062D1901 22.875
28.613079A20003 22.25
28.CF52142D1901 22.875

0.6546370983123779 sec

no matter whether Thonny or Bash.

Is there a Python3 library for RaspberryPi

Actually there is a problem when installing OWFS on Raspian Buster on PIs. File system an sensors appear in duplicates. I give you a link to the forum of the manufacturer of the used DS2482-100 adapter:

https://www.abelectronics.co.uk/forums/thread/303/owfs-duplicates

Regards

H. Wissing

Dr. med. habil. Dipl.- Ing. Heimo Wissing
Privatdozent, Arzt für Anästhesiologie,
Intensivmedizin und Schmerztherapie
Bioingenieur / Biomedizinische Technik
Neckarweg 1, 69118 Heidelberg
Tel.: 06221/801679 FAX: 06221/803738
mobil: 0171/4571292

Gesendet: Freitag, 13. März 2020 um 15:48 Uhr
Von: "Jan Kandziora" <j...@gmx.de>
An: owfs-developers@lists.sourceforge.net
Betreff: Re: [Owfs-developers] How to Use Simultaneous

Am 13.03.20 um 15:12 schrieb hwissing:
> Hello,
>
> I think one issue from the primary question is not answered..
>
> /" If I read from '/temperature' then I get them read in much faster
> *but I don't get a fresh conversion each time."*/
>
This is a very old question, and the mechanism has changed a bit since 2008.

>
> I have the same issue. First conversion with 8 DS18B20 sensors takes
> about 1 sec, immediately following requests take about 40 ms, but
> values are not updated. It takes a while till updated values are
> acquired, then conversion takes longer.
>
That is because you read /<ID>/temperature instead of
/uncached/<ID>/temperature

But don't do this either. If you want simultaneos conversions, do instead

$ owwrite /simultaneous/temperature 1
$ sleep 1s
$ owread /uncached/<sensor0id>/latesttemp
$ owread /uncached/<sensor1id>/latesttemp
$ owread /uncached/<sensor2id>/latesttemp
$ owread /uncached/<sensor3id>/latesttemp
$ owread /uncached/<sensor4id>/latesttemp
$ owread /uncached/<sensor5id>/latesttemp
$ owread /uncached/<sensor6id>/latesttemp
$ owread /uncached/<sensor7id>/latesttemp

Latesttemp has the resolution of the previous non-simultaneous
conversion, or, after power-up of the sensor, the resolution set in the
sensor's EEPROM. You can adjust the through /<ID>/tempres.

See the manpage: https://github.com/owfs/owfs-doc/wiki/DS18B20

Kind regards

Jan

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Re: [Owfs-developers] How to Use Simultaneous

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