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Original question:

BQ78350: BQ78350+BQ76930 debugging problem

BQ78350-R1: Cannot communicate with EV2400

Makoto Teramoto
Intellectual 295 points
Part Number: BQ78350-R1
Other Parts Discussed in Thread: BQ76940EVM, EV2400, , BQSTUDIO, BQ76940, BQ78350, TXS0102

I made a board of EV2400 and a part of BQ76940EVM by refering the schematic in the user guide of them.
However I could not communicate with BQ78350-R1 from bqstudio.

I could communicate with EV2400 board and could see the version of it (0.28). All leds lit.
And I measured the voltage of some point as follows. They looks fine, I guess.

[EV2400]
VCCs of MCP430 : 3.3V
High side of Pullup R (SMBC/D output) : 2.4V

[BQ76940EVM]
REGOUT of BQ76940(=VCC of BQ78350-R1) : 2.5V after BOOT
BAT of BQ76940 : 45V (applied)

Would you advice anything ?
Thank you in advance.

  • 0
    Intellectual 295 points

    I add some attachments.


    Regards,
    Makoto Teramoto

  • 0 in reply to Makoto Teramoto
    TI__Guru 54715 points

    Hi Makoto,

    You have several unknowns there.  It is usually easiest to debug something if you can separate something and introduce one unknown at a time.

    It seems you have the EV2400 working to USB with good voltage and firmware downloaded since it gives the proper version. The voltages seem low on the bus, I would expect more like 3 to 3.2V for a high level.  You might see if your gauge circuit is loading these. You mention the BQ76940EVM, if you have one of those separate from the circuit you built you might see if your EV2400 can talk to it and check the voltage levels on the SMB lines.

    For the BQ78350 circuit, check that the VCC is correct like the EVM.  If a 3.3V version of the BQ76940 is used  the gauge may be damaged.  Also check the address selection line, SMBA should be connected to VSS for normal addressing.

    The SMB voltage sounds unusual though, check the EV2400 circuit for proper connections, values & voltages.  Check the BQ78350 circuit for unusual voltages or loading on the SMB lines.

  • 0 in reply to WM5295
    Intellectual 295 points

    Thank you for your quick reply.
    In fact, I solved the issue myself last night.

    At first, I checked the SMB signals on the J2(SMB output of EV2400), and there were no signals.
    Then I checked SMB lines from there to MCP430, those signals are stopped at the level shifter IC (TXS0102).
    I made a wrong power connections of it. Those were VCCA>VCCB.
    I fixed them and then SMB signals reached to bq78350 finally.

    Now I can see the bq78350-R1 from my PC.

    There are some strange values in cell voltage (bq76940 is monitoring 15 series resisters but there are only 3 values),
    but I check my circuit again.If I can not solve this new issue, I might post another thread.

    Anyway, thank you again for your reply.

    Regards,
    Makoto Teramoto

  • 0 in reply to Makoto Teramoto
    TI__Guru 54715 points

    Hi Makoto,

    Glad to hear you found the issue.  The cell voltage reporting is fixed by setting the AFE cell map, see details in the BQ78350-R1 version Technical Reference.

  • 0 in reply to WM5295
    Intellectual 295 points

    Thank you for your advice about the cell voltage.
    I also fixed them by bqstudio. I can see all 15 values now.

    From now, I will explore and enjoy the bqstudio and AFE.

    Regards,
    Makoto Teramoto