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By default internal pull-up resistors for TWI SCL & SDA pins

raccoon

Why are the SCL and SDA pins by default (nRF SDK 11.0, nrf_drv_twi.c: 44-57) configured to use the internal pull-ups?

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    @rushin: That is correct. However the internal pull ups (13Kohm) may be too weak to work for all configurations. Together with the pin capacitance (4pF) you will start having problems for TWI frequency of 400KHz. The lines will be skewed. At 100KHz it will work fine.

    Generally, the pull up resistance on TWI is around 4.7K. If you have internal pull up resistors on the slave also it should work fine in most cases (13/2 = 6.5Kohm).

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  • 0

    @rushin: That is correct. However the internal pull ups (13Kohm) may be too weak to work for all configurations. Together with the pin capacitance (4pF) you will start having problems for TWI frequency of 400KHz. The lines will be skewed. At 100KHz it will work fine.

    Generally, the pull up resistance on TWI is around 4.7K. If you have internal pull up resistors on the slave also it should work fine in most cases (13/2 = 6.5Kohm).

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