Re: W1: w1_slave units, standardize 1C or .001C? Break API

[H. Peter Anvin]

H. Peter Anvin wrote:
> David Fries wrote:
> > The ds18b20 one wire temperature sensor conversion routine is
> > returning the units in degrees C while the ds1820 (ds18s20) is
> > returning it in .001 degrees C.  20C vs 20312C.  Once you know the
> > units I'm liking the latter as it gives a higher precision.  Time to
> > break user applications so the driver can give the temperature in the
> > same units for both sensors.
> >
> > I only have the ds18b20 sensor model.  Here is the current output from
> > the sys file for this sensor.
> > /sys/devices/w1_bus_master1/28-0000000e84a2/w1_slave
> > 45 01 4b 46 7f ff 0b 10 84 : crc=84 YES
> > 45 01 4b 46 7f ff 0b 10 84 t=20
> >
> > I ran the example data from the specification for the ds1820 through
> > it's conversion routine and found that t= was 1000 times the value.  
> > What should the displayed units be? 
> > This is the same ds18b20 conversion *1000.  Is everyone ok or is any
> > objecting to .001 degrees C for the units?  Patch will follow.  The
> > .001 C does truncate one bit of precision from the ds18b20 by the way.
>
> Millikelvins would have the nice property of never being negative.  :)

Alternatively, centikelvins would fit nicely in 16 bits if anyone cares...

655.35 K = 382.20 °C = 719.96 °F

	-hpa
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