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Original question:

BQ27Z561-R1: I2C Clock Stretching

BQ27Z561-R1: BQ27Z561-R1: I2C time out

Ryan Wang
Expert 7455 points
Part Number: BQ27Z561-R1
Other Parts Discussed in Thread: BQ27Z561

Shirish,

The questions are following below thread:

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1085867/bq27z561-r1-i2c-clock-stretching/4022213#4022213

We configured Qulcomm I2C pin as GPIO input pin after problem happen. SDA still keeps low which mean BQ27Z561 is pulling the SDA to low.

What might cause this phenomenon?

What can let BQ27Z561 release SDA?

Time out doesn't design for this scenario, right? In theory, time out only happen when SCL keeps low beyond 2s , right?

Great thanks

  • 0
    TI__Expert 7455 points

    Shirish,

    We confirmed the problem only happen when Qualcomm processor power cycle and reboot( 561 always has BAT attached.).

     Does below condition might cause this problem?

    1.  Qualcomm processor Power cycle happen at the middle of I2C communication, does this might cause this hang up? Or timeout can take care of it?

    2. During Qualcomm processor Power cycle, I2C pull up voltage will also down to 0V for a moment. It will back to 1.8V when power on. It should be no problem ,right?

    3. After problem happen, do you think we can use GPIO to send some CLK to SCL, SDA to resume 561 I2C state machine?

    This is in pre-mass production. Need your quick help on this.

    Great thanks

  • 0
    TI__Guru 57697 points

    Hello Ryan,

    It looks like bq27561 is expecting another clock. You can try sending a clock pulse and see if it fixes the problem. Root cause of such issue is usually not detecting clock stretch which makes the host go our of sync with bq27z561.

  • 0 in reply to Shirish
    TI__Expert 7455 points

    Thanks, Shirish