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BQ76PL455A-Q1: Connecting to exisiting bms modules

Peter Lingard
Prodigy 40 points
Part Number: BQ76PL455A-Q1
Other Parts Discussed in Thread: BQ76PL455A

Hello TI Support Forum. Please could you advise if I can connect direct to the bq76PL455A chip itself ((VIO,TX,RX, WAKEUP) not sure which GND to use though ??) pins to allow communication of my daisy chained modules? Also my battery packs are arranged as 5 in series which are paralleled to another 5 to double the capacity which begs the question do I daisy chain them as 10 in series or should I have 2 separate daisy chains and therefore 2 sets of comms? Thank you in advance. Peter

  • 0
    TI__Genius 17370 points

    Hi Peter,

    Can you clarify what you mean by direct connect to 455a as opposed to what? The 455a reference schematic may answer this,

    As for parallel cells, technically the 455 only connects to cells in series only, so it would be fine to connect the parallel cells to the same series connection to the 455 and so you dont need two separate chains. If you only have 5 cells in series, you may want to look into bq79606a instead as it provides 3-6 series cells with some other improved features.

    Best Regards,

    Taylor

  • 0 in reply to Taylor Vogt
    Prodigy 40 points

    Hello Taylor. Thank you for your reply. By direct connection I mean to the chip pins, not via an EVM or by the COMM+/- connections. By this I mean the TX,RX pins etc. I have download the GUI software and purchased a USB to TTL adaptor which therefore should indicate how I wish to connect... hopefully :-) I look forward to your reply, keep safe. Peter

  • 0 in reply to Peter Lingard
    TI__Genius 17370 points

    Hi Peter,

    You don't need to use our EVM or COMM connections for those pins but on your board you would need reference schematic required in the datasheet similar to EVM connections. The EVM comes with the USB to TTL adaptor connector port already installed so it makes it easy to plug in the GUI rather than blue wire each pin to the IC. Ensure you are using the correct FDTI adaptor required by the GUI (TTL-232R-5V).

    I recommend to check the bq76pl455a EVM user guide reference schematic and the pin functions table in the datasheet to see if any external connections/components are needed.

    Regards,

    Taylor

  • 0 in reply to Taylor Vogt
    Prodigy 40 points

    Hello Taylor. Thank you for your reply. I have the USB to TTL lead and can see when trying to run the GUI software the trasmit led flashes but I then get a message saying U'able to open comm port. I suspect the bms module is set to 250K baud but I cannot set that baud rate in Port Settins on my PC, can you advise please. Thanks in advance. Peter

  • 0 in reply to Peter Lingard
    TI__Genius 17370 points

    Hi Peter,

    To clarify - you have the exact cable I listed above? TTL-232R-5V. A generic converter will not work as it requires the specific FDTI drivers. Apart from that, please run through this thread checklist to determine if any of them may help:

    https://e2e.ti.com/support/power-management/f/196/t/655494?tisearch=e2e-sitesearch&keymatch=unable%20to%20open%20com%20port 

    Regards,

    Taylor

  • 0 in reply to Taylor Vogt
    Prodigy 40 points

    Hello Taylor. Thank you for your reply and information. I now have communication with my modules but the auto addressing seems to stop at 6 modules (0 to 5). Is there a setting in the software or registers where this can be increased please or does the GUI only support 6 boards ? Thanks in advance. Peter

  • 0 in reply to Peter Lingard
    TI__Genius 17370 points

    Hi Peter,

    Unfortunately our EVM/GUI user guide explains it allows up to 6 devices, stackable up to 96 cells. 

    Regards,

    Taylor