I did change to persistent and I didn't see a difference.
//settings/timeout/presence /is what is causing it. I had tried
changing it yesterday, via the httpd web page, but this time I checked
it with owread and that showed it still at 120, so I changed it to 20
with owwrite re-ran my Python script and yes it slows every 20 seconds
What is the purpose of //settings/timeout/presence/? The man page says
'Seconds until the /presence/ and bus location of a 1-wire device
expires in the cache.', but I don't really understand what it does.
Surely the presence is confirmed by any read of the sensor.
I have just tried setting it to -1, that is invalid, I thought it may
disable it. I set it to 0 and it is slow every time. I have now set it
to 9999999, not sure what the limit would be.
Comments?
Mick
//
On 06/08/2020 16:48, Martin Patzak wrote:
looks like you are getting close :-)
I checked, and the only timeout of owserver that matches 120 is
//settings/timeout/presence
/
On 06.08.20 16:21, Mick Sulley wrote:
Well this gets more curious. I am now measuring the time for each
read, reading type, power and latesttemp. Time for all is generally
< 0.1 seconds, but then when I hit the slow loop the read for type is
around 0.7 seconds, the others still < 0.1 seconds. I don't really
need type so I removed it and re-tested, on slow loops the power read
is around 0.7 seconds, latesttemp still < 0.1 seconds. So I removed
power as well, just reading latesttemp, on slow loops that is now
around 0.7 seconds. So it seems that at some point a sensor takes
many times longer for its next read, irrespective of which field is read.
I have now tested with 19, 11 and 2 sensors and the slow loop occurs
every 120 seconds. I am intrigued to know what causes this, any ideas?
Thanks
Mick
On 06/08/2020 10:23, Mick Sulley wrote:
OK I will log read times and see what that shows.
You say 'I also log if the error of the 1wire bus changes.' how do
you do that?
No I don't really need to read that fast, this is just a test setup
to get a better understanding so I can hopefully fine tune my main
system.
There should not be anything else running. I just tried running top
at the same time, I monitored it at the point of the slow scan and
didn't see anything else significant.
Mick
On 06/08/2020 09:06, Martin Patzak wrote:
It looks like your timing has improved after all!
in your original Python-code you could time every read for each sensor.
I have also powered sensors and a read is usually faster than 0.1
seconds.
I log in a file if the read took longer than 0.3 seconds, which is
almost never the case.
I also log in the file if the whole reading loop took longer than 3
seconds, which again is almost never the case.
I also log if the error of the 1wire bus changes.
I read 25 sensors every full and every half minute, so maybe you
could implement a delay as well and see if things get more consistent.
Do you need to read so fast in a loop for you application?
What else is running on your machine? You could run top in parallel
to your python loop.
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