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BQ76920: Unable to write bits to BQ76920 through I2C

Yean Khai Eng
Prodigy 40 points
Part Number: BQ76920

Hi, 

I am trying to write 0x19 to my BQ76920 CC_CFG register when the MCU starts up. However, the CC_CFG bits don't change after I wrote it. The same thing has happened when I was trying to change the PROTECT3 bits by writing 0xC0, and the PROTECT3 bits never change. I believe that the MCU I2C is working properly since it was tested with another I2C device and it works.

May I know if there is any possible cause that I can work on to solve this problem?

Thanks!

  • 0
    TI__Guru 54715 points

    Hi Yean,

    I see you are also having problems clearing a fault in another post, one possibility is that your I2C writes are not making it to the part.  That seems confirmed by your observation here. 

    I see you do not indicate the full part number, typically I understand the BQ76920 as BQ7692000 or BQ7692002, a non-crc version of the part.  If you have a CRC device such as BQ7692003 for example CRC is enabled and the proper CRC byte must be sent for the data to be accepted.  Single byte reads will work since the controller will clock in the data byte but not the CRC that the BQ7692003 was prepared to send.  Multiple byte reads will not work as expected since the 2nd byte read will be the CRC byte for the first data byte.  See the data sheet  section 10.3.1.4 Communications Subsystem.