If there is no way to distinguish 85 error/power up from 85 valid, you cannot
filter it. Period. It must all be done on the other side of owfs, and the user
strategy for this depends on application and expected results.
You could add flags like last_was_85, or a time stamp last_non_85, but this is
trivial to do elsewhere.
> On Jan 8, 2017, at 5:54 AM, Ekkehard Pofahl <ekkeh...@pofahl.de> wrote:
>
> Hello,
>
> I am using OWFS since more than two years in different versions on a Raspi 2.
> This alone shows, that I think it is a very good program.
>
> From time to time there is the "85 degree" discussion. It is a clear design
> flaw of the DS 18xxx chips to sent out a valid temperature reading, when an
> error code should be sent out.
>
> Everybody should be aware of the 85 degree flaw and mask it out,
>
> Previously I thought, 85 degree is only happening, if the power supply is
> insufficient, or shortly after power-on.
>
> BUT it seems, that within OWFS there are other ways to read 85 degrees.
>
> E.g. reading temperature value to quick after conversion command. This has
> been reported on also Arduino 1-wire software. Or something else ?
>
> I see the issue with OWFS Version 3.1p1 and 3.1p5. I did not check for other
> versions or parasite powered DS chips.
>
> Observation : the error code "85 Grad" is transmitted frequently with the
> DS18B20. Only two participants on the bus, stable power supply, no parasite
> power.
>
> Open OWFS issues :
>
> 1) make sure wrong timing is not provoking 85 degree readings on the OWFS
> server
> 2) filter out 85 degree "somewhere" in OWFS. Otherwise every user of the OWFS
> server needs to do that filtering.
> 3) do statistics on 85 degree reading
>
>
> pi@hsx03:~ $ date
> Thu 5 Jan 17:20:33 CET 2017
> pi@hsx03:~ $ sudo /opt/owfs/bin/owfs --version
> /opt/owfs/bin/owfs version:
> 3.1p5
> libow version:
> 3.1p5
>
>
> owhttpd readings :
>
>
> top highest level directory
> 28.28DBA7010000 28.28DBA7010000 directory
> 26.9D46F5000000 26.9D46F5000000 directory
> bus.0 bus.0 directory
>
> uncached version
> up directory
> address 2828DBA7010000A3
> alias
>
> crc8 A3
> errata errata
> family 28
> fasttemp 85
> id 28DBA7010000
> latesttemp 85
> locator FFFFFFFFFFFFFFFF
> power YES (1)
> r_address A3000001A7DB2828
> r_id 000001A7DB28
> r_locator FFFFFFFFFFFFFFFF
> scratchpad
> 50054B467FFF0C101C
> temperature 21.6875
> temperature10 85
> temperature11 21.75
> temperature12 21.6875
> temperature9 85
> temphigh
>
> templow
>
> tempres
>
> type DS18B20
>
>
>
> temperature 23.0625
> temperature10 85
> temperature11 23.125
> temperature12 23.0625
> temperature9 85
> temphigh
>
> templow
>
> type DS18B20
>
>
> temperature 23.1875
> temperature10 85
> temperature11 23.1875
> temperature12 23.1875
> temperature9 85
> temphigh
>
> templow
>
> tempres
>
> type DS18B20
>
> Sometimes everything is o.k. :
>
> scratchpad
> 72014B467FFF0E1057
> temperature 23.125
> temperature10 23.25
> temperature11 23.25
> temperature12 23.125
> temperature9 23.5
>
>
> I don't observe this on a DS18S20 :
>
>
> scratchpad
> 2E004B46FFFF0D10C4
> temperature 22.9375
> temphigh
>
> templow
>
> type DS18S20
>
>
> Best regards
> Ekkehard
>
>
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