BQ35100EVM-795: How to write to data flash

Part Number: BQ35100EVM-795
Other Parts Discussed in Thread: BQ35100, EV2400, BQSTUDIO


I am trying to configure the data flash parameters using the Advanced comm section of the GUI.

I have the device in accumulation mode and unseal full access.

I followed the instructions in the user manual but the value never gets updated.

Below is the log of my transactions:

Advanced Comm Transaction Log

TimeStamp , Read/Write , Address , Register , Length , Data ,
2021-04-01 10:03:11 814 , Wr , aa , 3e , 2 , b1 41
2021-04-01 10:03:20 111 , Wr , aa , 40 , 1 , 82
2021-04-01 10:03:31 999 , Wr , aa , 60 , 1 , 8b
2021-04-01 10:03:39 451 , Wr , aa , 61 , 1 , 05

What am I doing wrong? Or what other setting is required before writing to data flash.

  • Hello Buff,

    You can follow the instructions on this app note which walks through the steps needed to write to data flash for the bq35100:


    Wyatt Keller

  • Hi Wyatt,

    I have used the same document to test as the log above.

    The chem ID for my battery SAFT LS 33600 is not available and I read in another post from your colleague, Onyx, that I could use the default chem ID for EOS mode and change the cell design capacity. Using this doc I tried the example to change Operation config A register. This works programmatically but not using the EVM.

    I then tried to change cell design capacity in the manner below. This does not work programmatically or via the EVM.

    Is it correct to do this to get EOS mode for a larger cell of the same type?

    0x41FE Cell Design Capacity mAh

    write 3E FE41


    write 40 6842

    cs = 41+FE+4268=43A7

    last byte = A7

    inverted = 58

    write 60 58

    size = 4+2=6

    write 61 06

  • Hi Wyatt,

    I have been able to resolve the programmatic writing to flash of the 2 byte number. I see that I had to use each byte in the 16 bit value to calculate the checksum.

    I am still unable to do this with the EVM.

    Can you confirm my last point... i.e. that I should be able to get reliable readings using the default chem ID and changing the capacity to 17000?

    I will need to change my board and expose the I2C lines going to the BQ35100 in my next hardware spin to be able to use the EV2400 in production.

  • Hello Buff,

    Turn off Scan and Auto Refresh in bqStudio when writing and reading with Advanced Comm.

    In order to change Design Capacity to 17000 mAh, your commends should be:
    Write FE 41 to 3e;
    Write 42 68 to 40;
    Write 16 to 60; (FE + 41 + 42 + 68, invert last byte)
    Write  06 to 61;

    Best Regards,