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TWI SCL clock irregularity

I'm noticing some irregularity on the SCL line coming from my Nordic 52832. I've attached a Saleae logic trace here. What are the potential causes for this type of behavior?

ST54_init_I2C_trace.logicdata

  • We suspect that the pullups are too weak. We have answered the duplicate question in MyPage(case id 40611).

    Answer from MyPage:

    I was looking at the TWI trace data, and it looks like the pull-ups on the SCL and SDA lines are too weak for 400 kHz. Are you using the internal pull-resistors? These will limit the frequency greatly, and we recommend that you use external pull-up resistors in the range of 2.2k to 3.9k in order to use 400 kHz mode. For the 100kHz mode, the internal pull-ups (nom. 13k) will work without issues.

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