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USB-PD-CHG-EVM-01: Is there any problem with communicating directly with the BQ25792 via the I2C_SCL/ I2C_SDA lines?

Daniel Azubuike
Prodigy 20 points
Part Number: USB-PD-CHG-EVM-01
Other Parts Discussed in Thread: TPS25750, BQ25792, , BQ25792EVM, BQ25798EVM

I would like to retrieve ADC information and trigger the 'ship mode' via I2C. 

I see that you can read/write to the BQ25792 via the TPS25750 with the read/write transactions, on I2C1_SDA and I2C1_SCL. 

I was wondering if there is any disadvantage to communicating directly with the the BQ25792 (i.e connecting my MCU to the I2C_SCL/ I2C_SDA lines), rather than communicating through the TPS25750. 

Could this have any adverse affects on the system? 

Kind regards

  • +1
    TI__Mastermind 40305 points

    Hello,

    1. If you intend to use the ship mode of the BQ25792 you will be unable to on the USB-PD-CHG-EVM-01 as there is no ShipFet installed.

    2. The TPS25750 does not support two masters on the I2Cm lines. You could potentially run into bus collisions where the TPS25750 and the MCU are both trying to drive the bus at the same time. If you would like to communicate to the BQ25792, please do so through the I2Cs lines using the 4CC commands described in the Technical Reference Manual. This will prevent any communication collisions.

    Thanks,

    Mike Emanuel

    Please click "Resolved" if this answered your question.

  • 0 in reply to Michael Emanuel35
    Prodigy 20 points

    Thanks! 

    I have both the USB-PD-CHG-EVM-01 and the BQ25792EVM.

    I am using the USB-PD-CHG-EVM-01 to develop the comms with my MCU and the BQ25792EVM to test ship mode. 

    I am having some issues putting the BQ25792EVM into ship mode. 

    It is set up with the shunt and switch suggestions from the user guide, with a few changes. 

    I have a 2s battery pack connected to BATTERY and PGND on J5.

    A PSU is connected to J6.

    JP1 is connected to GND and JP3 is installed to bypass the MOSFET. 

    JP5 is not installed and pins 2-3 are shorted on JP8. 

    Apart from these, all the shunts are as 'BQ25792EVM, BQ25796EVM, and BQ25798EVM (BMS034) Evaluation Module' suggests. 

    I can communicate with the BQ25792 from my MCU. 

    When i read the 'REG11_Charger_Control_2 Register' i get '0x40' 

    I then write '0x45' to the reg. This should put the BQ into ship mode with no delay (setting SDRV_CTRL_1:0 = 2 & SDRV_DLY = 1). 

    Once this has been written to the register, i read it again. 

    It results in a value of '0x41'.

    It seems to be ignoring the ship mode bits, is there anything that i have missed? 

    Kind regards 

  • +1 in reply to Daniel Azubuike
    TI__Mastermind 40305 points

    Hello,

    You need to enable the Ship FET first.

    Please see REG14 for the SFET_PRESENT bit which needs to be set before trying to control the Ship FET.

    Thanks,

    Mike Emanuel

    Please click "Resolved" if this answered your question.