On 8 January 2017 at 14:59, Jan Kandziora <j...@gmx.de> wrote: > Am 08.01.2017 um 14:54 schrieb Ekkehard Pofahl: >> >> 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. >> > Ekkehard, I repeat this again and again and again and again… > > The 85°C readout isn't an error message. 85°C is default value which is > in the temperature register after power-on.
It is surely undeniable that this is a design flaw in the chip. Much more sensible would have been to make it default to full scale (or full negative scale), then it would have been much easier to program around. > ... > This has all been taken care for already, OWFS repeats a > .../temperature triggered conversion for the case 85°C is the result. > When you still have stray 85°C readings, it means your power failures > are so serious you should check your hardware setup. Is that still the case? I thought there was some discussion here recently about whether that code is in fact desirable and whether it should be removed. Perhaps I misunderstood the conversation. > > When you want to check for this particular problem, set the default > resolution of the chip to some resolution you never use by writing it to > .../tempres. After a conversion with a *different* resolution, and > encountering a 85°C reading, check whether the ../tempres value has been > reset to the default value. > > This is a poor man's POR flag. The chip lacks one, that's a design flaw. > > .../tempres is writeable since owfs-3.1p4 That is a good plan, thanks for that. Colin ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
