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BQ28Z610 acting as I2C master?

MingHui Kuang
Prodigy 20 points
Other Parts Discussed in Thread: BQ28Z610

Hello,

I am seeing something very strange with the BQ28Z610. I held our system microcontroller (the I2C master) in reset but I noticed the BQ28Z610 every 15 seconds or so generates 9 clock pulses and is trying to write to address 0xD4. Isn't this chip a slave only? What is it doing? There is no mention of this in the documentation.

  • 0
    TI__Expert 7895 points

    Hi MingHui,

    bq28z610 does have a Broadcast mode, where it transmits on the I2C bus as a master. See page 24, section 4.11 of the Technical Reference Manual for a description. It's designed to control an I2C charger on the same bus, writing the charge current and voltage to it. As you can see from Table 13.3.2, the default charger address it writes to is 0xD4, and the pacing is 15s, matching what you're seeing.


    By default, Broadcast mode is enabled disabled (BIT0 of I2C Configuration register, 0x4602). Double check your code to make sure the BCAST bit isn't being set on accident.

    Jonathan

    EDIT 06/10/16: Bold / strikeouts made with new information.

  • 0 in reply to Jonathan Bender
    Prodigy 10 points
    Hi Jonathan,

    Yes we figured that one out last week. We turned it off.

    By default the BCAST bit is enabled per the BQ28Z610 reference manual page 110. The default is 0x01.
  • 0 in reply to MingHui Kuang83
    TI__Expert 7895 points
    Hi MingHui,

    Glad you were able to get it resolved. It looks like there's an issue with the documentation - as you mention, it shows 0x01 as the default register value on page 110, 0x21 as the default on page 88, and the description states that BCAST = 0 by default on page 88. Will make sure this is addressed in the next TRM revision to reflect the actual device's defaults.

    Jonathan
  • 0 in reply to Jonathan Bender
    TI__Expert 7895 points

    Hi MingHui,

    I've confirmed that bq28z610 is configured with Broadcast mode enabled by default. The documentation has already been corrected internally, so those corrections will be visible in the next official TRM revision.

    Jonathan

  • 0 in reply to Jonathan Bender
    Prodigy 20 points

    Hello,

    How can I disable bq28z610 broadcast mode by default.

    Thanks,

  • 0 in reply to karlt
    TI__Guru* 76230 points

    Hello KT

    The technical reference manual of the device discusses in detail the broadcast functionality of the device. By clearing the BCAST bit, you disable the ability of the gauge to broadcast to a host or smart charger.

    The BCAST bit is located in the i2c configuration register of in the configuration  section contained in settings in data flash.

    thanks

    Onyx