Attachments (0)
Nordic Case Info
  • Case ID: 119424
Options
This post is older than 2 years and might not be relevant anymore
More Info: Consider searching for newer posts
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

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?

Parents
  • 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).

  • 0 in reply to Ole Bauck

    Maybe I need to clarify things. Since we have external pull-ups for the SDA and SCL lines (I understand that the internals are not an option) why would you want to also have the internal pull-ups enabled?

Reply
  • 0 in reply to Ole Bauck

    Maybe I need to clarify things. Since we have external pull-ups for the SDA and SCL lines (I understand that the internals are not an option) why would you want to also have the internal pull-ups enabled?

Children
No Data
Terms of service