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BQ76PL455A-Q1: User checksum Error

Danyal Yitik
Prodigy 100 points
Part Number: BQ76PL455A-Q1
Other Parts Discussed in Thread: BQ76PL455A

Hello,

 

I have a question regarding one specific error I keep having. I managed to make my two bq76PL455A ‘s work properly, that is I can give them addresses, assert GPIO pins, read voltages, etc. However the FAULT_N pin will never go high indicating a fault condition. Upon reading the fault registers the devices suggest a “USER_CKSUM_ERR” in the Chip Fault register. For the CRC-bytes I send form the host microcontroller I even used the CRC-generator web tool that was recommended by the Softwareguide for the devices and switched the order of the two CRC bytes like it was described in that document. I double and triple checked every sent message and the CRC bytes should be correct, but I keep having the same fault. Ignoring the FAULT_N pin is no option, since I plan to use it as a hardware safety feature.

 

Can someone please tell me what I am overlooking or doing wrong?

 

Thank you in advance !



Regards


Danyal Yitik

  • 0
    TI__Genius 10785 points
    Fault_N is active LOW. Meaning that you have FAULT condition already and didn't clear the Fault.
    You have to clear all your FAULT condition then it will go back to high.
  • 0 in reply to Roger Hwang
    Prodigy 100 points
    Hello,

    thanks for the quick answer but I think there was a misunderstanding regarding the FAULT_N signal. I know what active low is and what it means : )
    However the first thing I do is clearing the Fault Summary Register to clear all fault conditions, but the FAULT_N pin won’t go high. Additionally the data sheet says that the USER_CKSUM_ERR is self-clearing when the condition goes away, which it doesn’t. I think it has something to do with the CRC bytes I’m sending but I don’t know what exactly.

    Thank you in advance !


    Regards

    Danyal Yitik
  • 0 in reply to Danyal Yitik
    TI__Genius 10785 points
    I think you are doing right thing by clearing FAULT.
    So, is USER_CKSUM_ERR only fault you seen now.

    let's do this in two steps.
    1. Mask this fault and see FAULT pin goes high.
    2. It will clear is if you have unlatched and mismatch no longer occurs. For example, you can turn on the cell balancing with timer then you will have cksum fault but if you set back to original setting then it will clear it. This is only true for unlatched fault condition.