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BQ27427: Golden image calibration files

David Burgess
Prodigy 11 points
Part Number: BQ27427
Other Parts Discussed in Thread: BQSTUDIO

Tool/software:

The battery management studio outputs two "golden image" calibration files xxxx.ot.fs and xxxx.gm.fs

I see "ot" seems to stand for "one-time" flash stream - not sure what "one-time" is supposed to mean

and "gm" stands for "gauge mode" flash stream - again not sure what "gauge mode" means.

I can decode the "gauge mode" gm.fs file it shows programming of most of the subclasses for the bq27427 (but not all) - I create 'C' code array declarations from this for each subclass.

  • It does not include the CC_CAL subclass registers, in particular CC Gain (Which isn't even mentioned in the bq27427 documentation)
  • It does include a subclass 68 (Which is not mentioned in documentation for the bq27427, but is mentioned for the bq27421as a power register with settings to place it in HIBERNATE mode (The bq27424 does not have a HIBERNATE mode , only SLEEP which is controlled by the "Sleep Current" (Subclass 82, offset 23))

I can't make sense of the xxxx.ot.fs file - it seems to be writing to completely different registers.

There IS an option in BMS to include CC Gain in the xxxx.ot.fs file - but as I said I can't decode this.

Could you point me to information on how to interpret values in the xxx.ot.fs file ? (I know the W:, X: and C: commands, but the values don't make sense - W: 16?? )

Do I need to program values for subclass 68 (Power) for the bq27427 ?

How do I get BMS to output values for the CC Cal subclass ? (I already know I have to flip the sign on CC_Gain in order to get correct current and SoC measurements)

Thanks in advance for any help you can give.

David

  • +1
    TI__Mastermind 37761 points

    Hello David,

    You should not have to program the ot.fs file. You should only have to program the gm.fs file since that contains all the configurations for the gauge. 

    In BQStudio you need to go to Window -> Preferences -> Golden Image and then make sure that this field is cleared. 

    Regards,

    Adrian

  • 0 in reply to Adrian
    Prodigy 11 points

    Thanks for the reply Adrian and confirming I only need the xxx.gm.fs file

    I looked in preferences > Golden Image. It had class names to be preserved as "Calibration". So I deleted that and recreated the files.

    It now puts out values for the Calibration class: Data (subclass 104),  CC_Cal (subclass 105), and Current (subclass 107)

    Thank you so much for helping with this.

    Incidentally, my CC_Gain value is 0x7F32FEC5 = 0.3496, which at least now has the correct sign.

    Th documentation for BQ27427 on the CC Cal subclass only mentions CC Cal Temp. I would think it needs to be updated to include the additional parameters. Where are they currently documented ?

    Also I'm still programming subclass 68 (Power) but I don't think it has meaning for this chip. Can you confirm ?

    David

  • +1 in reply to David Burgess
    TI__Mastermind 37761 points

    Hello David,

    Unfortunately, other calibration parameters are not documented. We recommend using BQStudio for calibration as all the necessary parameters will be updated.

    For the power section, if you didn't change any of those values from the default value then you don't need to program it.

    Regards,

    Adrian