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BQ76920: The battery voltage can be read, but the configuration register can not be read, may I ask if the chip can only read data register.

?? ?
Prodigy 10 points
Part Number: BQ76920

As shown in the figure，SYS_CTRL1 register  can be written correctly, but it cannot be read correctly. The data register can read the battery voltage normally. Therefore, whether the bit configuration register cannot be read or needs to be unprotected when reading.

  • 0
    TI__Genius 14035 points

    You should be able to read from 0x04 with no problems. Do you have an EVM to test on? Have you looked at our example code for reference?

  • 0 回复 Eirwen
    Prodigy 10 points

    Thank you for your answer. Could you please provide the address or source file of the  code? I can't find it on the official website

  • 0 回复 ?? ?
    TI__Genius 14035 points

    You can find it in the device's product page:

  • 0 回复 Eirwen
    Prodigy 20 points

    hello, im his colleague，i can describe this problem to you deeply.
    we dont use TI CPU like msp430 but another chip.
    This is our IIC transfomation function

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    rt_uint8_t
    BQ76920_ReadOneByte (rt_uint16_t ADDR)
    {
    rt_uint8_t temp = 0;
    BQI2C_Start ();
    BQI2C_SendByte (0x10);
    BQI2C_ReceiveAck ();
    BQI2C_SendByte (ADDR);
    BQI2C_ReceiveAck ();
    BQI2C_Start ();
    BQI2C_SendByte (0x11);
    BQI2C_ReceiveAck ();
    temp = BQI2C_ReceiveByte ();
    BQI2C_SendAck (1);
    BQI2C_Stop ();
    return temp;
    }
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

    We are going to use this in our status detecting functions
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    unsigned char BMS_sta, DSG_STA, CHG_STA, DSG_STA_FLAG, CHG_STA_FLAG;
    void
    BMS_STA (void)
    {
    BMS_sta = BQ76920_ReadOneByte (SYS_CTRL2);
    DSG_STA = BMS_sta & 0x02;
    CHG_STA = BMS_sta & 0x01;
    }
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

    But we found that when BQ76920_ReadOneByte is working, the register address can be sent normally, but the register value received by the function is 0x00, thats the problem.

    By the way, our WriteOneByte function can work normally, heres the code.
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    void
    BQ76920_WriteOneByte (rt_uint16_t ADDR, rt_uint16_t DataToWrite)
    {
    BQI2C_Start ();
    BQI2C_SendByte (0x10);
    BQI2C_ReceiveAck ();
    BQI2C_SendByte (ADDR);
    BQI2C_ReceiveAck ();
    BQI2C_SendByte (DataToWrite);
    BQI2C_ReceiveAck ();
    BQI2C_Stop ();
    rt_thread_mdelay (10);
    }
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

    We need help, and if you want some other information please reply, thank you:

  • 0 回复 G_Zhao
    TI__Genius 14035 points

    Are they sending CRC? This device requires CRC to communicate properly. The TI sample code should serve as an example for their own code, as it implements the CRC function in it.

  • 0 回复 Eirwen
    Prodigy 20 points

    First in this type CRC is optional, and we try to send CRC but the problem still exists.

  • 0 回复 G_Zhao
    TI__Genius 14035 points

    CRC is not optional in this device when writing. You require CRC to write.

    See Question 6.5 Can I use the CRC part without CRC? of the bq76920, bq76930, bq76940 AFE FAQ.

    I would advice that you test using an EVM to ensure it all works properly. The sample code should function as an example to implement in your own code.