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BQ78Z100: Unseal Process

Mirko Rummelhagen54
Prodigy 10 points
Part Number: BQ78Z100
Other Parts Discussed in Thread: BQSTUDIO

I've got a bunch of BQ78Z100 (Firmware Version 4), which i need to configure and calibrate. After this process the Unseal Key and Full Access Key are changed and the BQ78Z100 is sealed.

For testing purposes i would like to unseal BQs again. I tried to write the first Word of the Key to AltManufacturerAccess and then the second Word like stated in Chapter 9.5.2 of the Technical Reference. I tried changing the first and second word and i tried different byteorders. 

Furthermore, even when using BQ Studio (Auto Refresh turned off), i could not unseal the BQs.

While the BQs are unsealed, I am able to read the Keys. So I am sure, I've got the right Keys.

What is the right process for unsealing the BQ78Z100 via I2C? How long do I need to wait between writing the words to AltManufacturerAccess? Is writing the words after each other to AltManufacturerAccess even the correct procedure?

  • 0
    TI__Mastermind 42535 points
    For unsealing the gauge you will have to write to Alt Manufacturer Access using bqstudio with auto refresh turned off. Make sure that your dashboard has also been disabled. The dashboard when enabled will have a green bar which when clicked will turn red and will not scan the device. Once you have done that, send the unseal code first. When you scan the status bits should indicate the gauge is unsealed. Then send the full access code and scan again. Now the gauge will be unsealed and also be in full access mode.

    You don't need to wait between writing the words, I suggest it so that you can check the gauge status during the process.
  • 0
    Expert 1015 points
    Hi Mirko,

    In case you or anyone else is looking for answers to this, I was recently able to perform the unseal using firmware.

    After spending an hour trying to use Advanced Comm in bqstudio to try to unlock - p47 of technical reference says the 2nd key must be sent within 4s of first key, I gave up and tried to perform the unlock using firmware code in my microcontroller. I was able to perform the unlock by performing the following two I2C transactions.

    Send to 0x3E 0x14 0x04 to the 78z100 (address 0xAA)
    Send to 0x3E 0x72 0x36 to the 78z100 (address 0xAA)

    This unsealed the 78z100 and I was able to reset the 78z100. Hope this helps someone.