[lkml]   [2004]   [Jul]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRE: --- (or anyone else) one small i2c question.
    Hm, Greg must be on virtual holiday.


    Anyone else, then alive?

    I hope open source doesn't mean "Closed community :)"
    Here I am. I want to contribute some code. But I need some help, because not
    everything can be done alone on this planet. Sometimes you need guidance.

    It's better to talk, and send people away on a search, then to ignore

    And all I want is some small help with i2c.


    -----Original Message-----
    [] On Behalf Of Reinder
    Sent: Saturday, July 17, 2004 16:30
    Subject: Greg (or anyone else) one small i2c question.


    While having some fun, with the old 2.4 vt8231, ""porting"" that to the 2.6
    Branche, my eyes raised some strange question, which I hope you can answer.

    From the Sysf-Interface, it states:

    temp[1-4]_max Temperature max value.
    Unit: Milidegrees Celsius
    Read/Write value.

    I far as I know, one Milidegrees is one thousand Grade Celsius.

    The actual Reading, from the vt8231 inside the io space is an 8 bit value.
    It contains for example a number "78" in "Celsius" for de 1f CPU temp

    Now, from various documentations floating around, for some undocumented or
    well hidden reason, this mostly is multiplied by 0.88 giving a reading of

    I assume somebody thought about it and calculated that m that was a nice
    correction value.

    Converting it to the required units, would be 68.84*1000 = 68840
    Or, to avoid Floating points: ( (68*1000)*880)/1000 = 68840 Milidegrees

    That was, when life was easy.

    However, my bet is somebody figured out, that bit 7 till 6 in the reserved
    area from area 4b, contains also bits of temperature information. (Although
    the datasheet I have, describe that area as "Reserved")

    The value is readed, Anded with 192, then shifted to right by 6 to get the
    reading. "0,1,2,3". We assume the value is 3.

    Assuming that, this Value is stored in the same Magic Celsius Value,
    Multiplied by 880, this gives a correction of 2640 Milidegrees.

    That is, if it where separate 8 and 2 bit values. But As I can see, from the
    original code, it assumed as 1 10bit value.

    Thus the first value 79 is shifted to left by 2, and the second value is
    orred into it. Which gives (79>>2) = 316.
    Plus the low value "3" = 319

    Returning, this, in the old version, to Human readable format, it was
    multiplied by 10, and then divided by 4. Giving 797.5

    I assume, that something has changed, with the sensor output format.
    Thus, the new return formula would be:
    Multi by 1000, divide by 4.
    Now we have 79750.

    Throwing in the 0.088 Correction Factor the final result is:
    79750* 0.088 = 70180 Milidegrees Celsius

    Or 319 * 880 /4 = 70180

    Or 319 * 220 = 70180

    If this was "temp3" , it would result in 1 sensors.conf line:

    Compute temp3 @

    Is my final concussing Right?

    If so, I will move on to the voltage part :)
    If not, I Hope somebody can point me out where to go...

    Reinder Kraaij.

    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

    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: 2005-03-22 14:04    [W:0.033 / U:3.792 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site