[lkml]   [2008]   [Jan]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: W1: w1_slave units, standardize 1C or .001C? Break API
    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

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2008-01-22 04:31    [W:0.275 / U:3.740 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site