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Original question:

BQ76942: EVM2400 with SPI bus

BQ76942: Initial configuration/prototyping and interfacing with MCU, "in situ"

Oscar Walsh
Prodigy 100 points
Part Number: BQ76942
Other Parts Discussed in Thread: EV2400, BQSTUDIO

Hi,

I am updating the design of an existing battery-powered product, possibly replacing the existing passive battery management circuitry with the BQ76942 for more functionality. 

The product uses an STM32L4 MCU, which would interface with the BQ76942 over SPI (thus it will be an SPI-default version of the BQ76942).

Seeking guidance on 2 main questions:

  1. What would be the best way to initially configure and program the BQ76942, connected to the STM32 MCU? I know that an evaluation module exists, but I want to be able to configure and tweak the BQ76942 "in situ," on the prototype product PCB. Would the EV2400 interface allow me to connect directly to the BQ76942 (over SPI) and program it (via BQ Studio), while it is on the prototype product PCB? Ideally I'd be able to tweak a setting in BQ Studio, then disconnect the EV2400 and evaluate the BMS's performance on the prototype PCB. I could include jumpers to allow selection between connecting the BQ76942's SPI to the STM32 MCU or to the external EV2400 interface.
  2. Assuming the 'perfect configuration' is found, what would be the best method to program the BQ76942 chips OTP in production? What would the process physically be? Would it be done 'in situ', or before the chips were soldered to the PCB?

Thank you!

  • +1
    TI__Mastermind 23081 points

    Hello Oscar,

    1- We have a start-guide microcontroller code example for the BQ769X2 device family on the product page. This includes the starting code for STM32 using SPI. I will attach it here. sluc701a (2).zip

    Oscar Walsh said:
    Would the EV2400 interface allow me to connect directly to the BQ76942 (over SPI) and program it (via BQ Studio), while it is on the prototype product PCB?

    Yes, you can use your prototype board along with the EV2400 to communicate with BQStudio. This will actually make it easier to configure the settings.

    2-  Typically there's a different board to do OTP, simply because OTP cannot be done with cells attached. But, as long as OTP conditions are met, it is fine to do OTP on the soldered PCB. More about OTP and conditions can be found in the Calibration and OTP programming guide and also in the OTP FAQ.

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    Prodigy 100 points

    Thank you! One other question: if I were to get the BQ76942 Evaluation Module (instead of the EV2400), would I be able to use the microcontroller on this to interface with other BQ76942 ICs? i.e. since the EVM interfaces with BQStudio, could I use it instead of the EV2400 for BQ76942 ICs that aren't on the EVM?

  • +1 in reply to Oscar Walsh
    TI__Mastermind 23081 points

    Hello Oscar,

    The BQ76942 Evaluation Module comes with the EV2400 integrated on the board. 

    Oscar Walsh said:
    since the EVM interfaces with BQStudio, could I use it instead of the EV2400 for BQ76942 ICs that aren't on the EVM?

    Yes, I have seen customers do this. This can be done, just need to be careful with connections and remove the on-board shunts for uC_SCL and uC_SDA as you don't want to be talking to both ICs (on-board and off-board)

    Regards,
    Jose Couso