This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ27421EVM-G1A: Writing a opconfig register

Part Number: BQ27421EVM-G1A
Other Parts Discussed in Thread: BQSTUDIO


Can I overwrite opconfig register's default settings? Is it a good idea?

If it is possible, how can I approach towards it?



  • Yes, you can.  The easiest way is to use bqStudio.
  • I have taken logs of charging cycle for BQ27421 with the wall charger. Could you please check the attachment!!

    There are following queries need to be addressed:

    1) Why fuel gauge is switching between sleep mode and normal mode?

    Nothing in the firmware which controls the average current. It simply reads from  AverageCurrent().

    2) In every charging cycle from 89% it will shoot up to 100% directly.

    What is the reason of sudden change?

    3)OpConfig: 0x25F8 (already set to default value)

    So,what is the other option than BQstudio to rewrite it?

    According to TRM sluuac5c the OpConfig is read only register.(Table 5-1. Extended Commands)

    Kindly go through the attachment.

    It will be really helpful to get the cause of the issue.



  • Hello Netraja,

    1. The gas gauge does this automatically. You will need to check the sleep current settings.

    2. The jump is due to FC set, you can run it for a few more cycles, but make sure you follow the primary charge termination rules on the TRM.

    3. You can change it with the TRM. It is changed in RAM.

  • Hello Kang Kang,

    Could you please tell me what are the conditions under which average current of fuel gauge become zero apart from average current < sleep current condition?

    The OpConfig register is set to 0X25D8 (SLEEP=0), so fuel gauge does not go to the sleep mode.

    But whenever charger is connected, the average current becomes zero for some particular time then it shows the positive value. This happens frequently.

    What are the possible conditions due to which average current frequently goes zero.

    Thank you!



  • Hello Netraja,

    The average current will be zero when it is in the deadband or there is no current flowing.

    Are the pulses of current in your log programmed or is this the error you're talking about? Your average current value should not be frequently going to zero, check your communication and hardware connections to make sure they are secure.


    Wyatt Keller