Am 05.10.2015 um 00:45 schrieb Loren Amelang: > > I noticed in "28.D64788000000/errata": --- up directory die > C2 trim 48077 <-- trimblanket trimvalid NO (0) <-- but > uncached or reload showed YES... --- > > While in "28.884D88000000/errata": --- up directory die C2 > trim 48117 <-- trimblanket trimvalid YES (1) --- > > I have no idea what that means. > That may be the culprit.
These errata initially only applied to the B7 die. But the C2 die has another bug, it sometimes doesn't load the factory calibration values from EEPROM on POR, resulting in wrong temperature readout. http://osdir.com/ml/hardware.one-wire.weather/2005-11/msg00045.html So if your bus setup is brittle and you get more PORs, it's more likely you trigger the bug and the chip doesn't load the calibration values. Writing trim values issues the said 0x64 command to the chip but I'm not really sure if that's what we want, always writing a new value. For the B7 die that's the way to go but for C2 problem, it's just too invasive, I think. Maybe a new owfs node which just issues the 0x64 command, as David suggested? > It offers to let me change the trim, > so it must be an OWFS parameter rather than something read from the > chip. > No, it's read from and written to the chip. > If it is applied to the temperature reading, maybe that > explains my remaining difference? Except the 48077 factor reads > higher than the 48117 factor... > These aren't factors, valid trim values follow the pattern 10111011xxxxx011 or 10111011xxxxx101 So there are only 64 of it. > > Statistics -> Errors shows: NET_connection_errors 1 > > But bus.0 -> Statistics -> Errors shows: CRC8_errors 11 > CRC8_tries 409 > > The bus.0 page also shows both sensors, so I assume it is the active > buss. While I've been writing this, "tries" has gone from 409 to 427. > The system has been up since Feb 2015, so maybe those numbers are not > all-time cumulative? Maybe just since the HTTPD was connected? But in > any case, they are not evenly spaced in time - that jump happened all > at once, and 427 has remained since. (Later it is 449.) > > If error values were being averaged in, would they show in the > Statistics? > Never looked into these counters too deeply, sorry. If it really matters, I will. > > I guess the other option is that some internal part of a DS18B20 is > actually analog, and influenced by marginal bus power. > Sure the heat sensor is an analog part, but it has a compensated current source. It wouldn't work at all if bus voltage ever mattered. Kind regards Jan ------------------------------------------------------------------------------ _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
