I2C and pinctrl

[KRich]

While migrating my project to use the new pinctrl mechanism in I ran into an issue where the I2C communication on some busses was not working. Further investigation revealed that I needed to add the `nordic,drive-mode = <NRF_DRIVE_S0D1>;` property to my pinctrl definitions for the relevant signals. This makes sense since the TWIM driver no longer forces any configuration of the pins, but this discovery made me wonder...

Why is the `nordic,drive-mode` not set to S0D1 for all of the I2C signals in the devkit pinctrl files like `nrf5340_cpuapp_common-pinctrl.dtsi`? Wouldn't any I2C pin really want/need to be configured for that drive mode?

[Joakim Jakobsen]

Hi!

I agree, S0D1 has been the default and would work for most I2C configurations.

Talked to one of my colleagues about this; And it seems that the driver sets skip_gpio_config. So it should have been done for pins configured for TWI/I2C.

This is probably just be a bug from moving to pin control. I'll talk to our developers and get back to you.

Br,
Joakim

[Øivind]

Hi,

We are looking into this bug now. At the moment we have only seen the issue on nrf52833. Are you seeing the issue on an nrf5340 DK? If so are you building for secure or non-secure?

[Øivind]

Zephyr has a PR up for this now:

https://github.com/zephyrproject-rtos/zephyr/pull/47145