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BQ40Z50-R1: Communication problems with BQSTUDIO

Luis Pinillos
Prodigy 220 points
Part Number: BQ40Z50-R1
Other Parts Discussed in Thread: BQSTUDIO, , EV2400

Hello,

I am working with the BQ40z50-R1 to build a BMS for a lithium battery pack. The battery pack has a 3S cell configuration, each cell has a nominal voltage of 3.7V. After receiving the circuit from a third party company that designed the BMS, I can't seem to connect to BQSTUDIO since it doesn't recognize the BMS. When I try connecting the cells to the BQ40z50-R1 EVM it works perfectly, so I'm guessing the problem is either the way the PCB was made or something in the configuration the designers programmed. Also, to communicate I am using the EV2400. Attached find a section of the schematic showing how the SMB pins were connected.

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If the connection is ok (I already verified in the PCB it is indeed connected as shown), is there anything in the configuration that could cause a permanent shutdown? Any suggestion on what to do would be appreciated.

Thank you very much,

Luis

  • 0
    TI__Mastermind 34775 points
    Hi Luis,

    bqStudio tries repeatedly to communicate with bq40z50-R1 on your PCB. Have you tried looking at the SMBD and SMBC signals on a scope to see that they are switching high and low and whether the bq40z50-R1 acknowledging or not? It looks like you're missing the pullup resistors on SMBD and SMBC lines. You can refer to the EVM schematic in bq40z50EVM user's guide.

    Did you apply a voltage across the PACK pins to wake up the gauge? It can be done by shorting BAT to PACK+ briefly.
  • 0 in reply to Damian Lewis
    Prodigy 220 points
    Hi Damian,

    Thank you for answering. I checked the schematic for the BQ40z50-R1 EVM and I can't find any pull-up resistors, I measured the voltage between Vss and SMBC and SMBD and both showed 0V. Also, I could communicate by replacing the BQ40z50-R1 with a new one, maybe the one they sent us in the PCB was damaged?

    I did try to wake it up by shorting Bat and Pack +, but it didn't work. I could only do it with the new one. I talked to the people who designed the BMS so they could send me the parameters that were written in the Flash Memory, and when I try to write the data I get the following error:

    Parameter not written. Classname Settings, Subclass name Configuration, Parameter name Balancing Configuration written to data memory failed readback verification.

    Also, I can't calibrate the BMS because I get the following error:

    Calibration - A read of data written failed comparison.

    Is there something I have to do previous to writing the parameters send by the manufacturer?

    I appreciate your help!

    Best regards,

    Luis
  • 0 in reply to Luis Pinillos
    TI__Mastermind 34775 points
    Hi Luis,

    Ok there's pullups in the EV2400, but make sure your host has pullups on these lines. They may have damaged the gauge during assembly.

    Is the gauge sealed? What's the status of the SEC1 and SEC0 bits?

    SEC1, SEC0 (Bits 9–8): SECURITY mode
    0, 0 = Reserved
    0, 1 = Full Access
    1, 0 = Unsealed
    1, 1 = Sealed

    If it sealed, you will need to have full access to program it. You can try using bqStudio and send the unseal followed by full access commands in the right side column to try default code. If that doesn't work then the manufacturer will have to provide the codes to you.
  • 0 in reply to Damian Lewis
    Prodigy 220 points

    Hi Damian,

    I am using the EV2400 to test it at the moment so it should work fine, I will make sure the host has the pull-up resistors.

    The gauge has SEC1=0 and SEC0=1, but I keep getting the same error, when I try to change something individually I get "A read of data written failed comparison" and if I try to import the *.gg.csv file and write it to flash, I get the readback error.

    Do you think I should try to replace the one I just soldered with a new one?

    Thank you for your help!

    Luis

  • 0 in reply to Luis Pinillos
    TI__Mastermind 34775 points
    Hi Luis,

    Try reprogramming the default srec then import the gg.csv file. If that doesn't work then try replacing the device on your board.

    You can get the latest FW srec file here:
    www.ti.com/.../sluc585