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.

BQ76905EVM: Seal to Full Access the device

Part Number: BQ76905EVM

Tool/software:

We were trying to Full access the device by using Security Keys command along with the checksum, but the device couldn't be unsealed:

Following is the steps followed:

1. The device is sealed using 0x0030 command

2. The Full access key 1 sent 0x1404 to the address 0x0035 along with check sum 0x60 0xB2 0x06

3. The Full access key 2 sent 0x3672 to the address 0x0035 along with check sum 0x60 0x22 0x06

Checked in the battery status device still it was sealed only.

  • Hi Pranav,

    When sending the Fullaccess keys to unseal the device, you write the keys directly to 3E/3F and you do not send a checksum for them.

    Regards,

    Max Verboncoeur

  • Thank you for the reply

  • For the command sequence above, the device is not unsealed. The sequences attempting to unseal it are as follows:

    1st Sequence:

    1. W: 10 3e 30 00 /* Seal the Device */
    2. W: 10 3e 14 04 /* Unseal the Device */
    3. W: 10 3e 72 36

    2nd Sequence:

    1. W: 10 3e 30 00 /* Seal the Device */
    2. W: 10 3e 14 04 /* Unseal the Device */
    3. W: 10 3e 72 36
    4. W: 10 3f 14 04
    5. W: 10 3f 72 36
  • Still device is in Sealed State in battery status.

  • Hi Pranav,

    You do not need a separate pair of commands to write the keys to 3F. The command [W: 10 3E 14 04] will write 0x14 to address 3E, and 0x04 to address 3F.

    The first sequence should work, the second sequence may not work if the keys are being overwritten before the device checks them.

    Also make sure to refresh the registers page after sending the command to update the readout.

    One thing to note, I tested the sequence I sent before on an EVM and it works as expected, so if the first sequence is not working, you may want to check the communications with a logic analyzer.

    Regards,

    Max Verboncoeur