Software I2C / switching I2C pins while runtime

[JonasGel]

Hello Nordic Team, 

We haven chosen a nRF52805 SoC and MDBT42T Module and would like to operate with 2 i2C sensors on two different Pin-pairs.
Since the nRF52805 only has one i2c bus, i would like to use software i2c and use 2 different pin pairs or use this one bus and operate witch each sensor at a time and change i2c pins.

Do you have code examples for soft I2C and changing I2C Pins on &gpio0 while runtime? Or suggestions, which proceeding is the better one? 

[Michal]

Hello Jonas,

The absolute easiest way would to be to put both sensors on one I2C bus. Even if it the exact same type of sensor, there is often a way to change the address by pulling a pin to either supply voltage or ground.

If it is still not possible, then yes, it is possible to switch the I2C pins during runtime or use a software/bit-banging I2C implementation.

I am going to assume that you are using NCS 2.0.0 and the new default Pin Control (pinctrl) API.
Please remember to always state the version of NCS you are using so that we know which features are available to you.

For hardware implementation you would have to use Dynamic Pin Control. Just remember to suspend the I2C peripheral before switching the pins.

I would highly recommend reading the pinctrl documentation
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.0.0/nrf/ug_pinctrl.html

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.0.0/zephyr/hardware/pinctrl/index.html

The second link includes a section about dynamic pin control:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.0.0/zephyr/hardware/pinctrl/index.html#dynamic-pin-control

A sample utilizing dynamic control:

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.0.0/zephyr/samples/boards/nrf/dynamic_pinctrl/README.html

As for a software I2C, there was a driver in nRF5 SDK (components\drivers_nrf\twi_master\deprecated\twi_sw_master.c), but I don't think we have any in NCS, so you would have to implement your own.

Hope that answers your question.

Best regards,

Michal

[JonasGel]

Thanks Michal, 

I have tested dynamic pincontrol in SDK 2.0 but struggled a little with the implementation.
And because it actually only should be used during startup, I watched out for an alternative. 
I Implemented it now successfully with the gpio-i2c driver and will later measure current consumption of this implementation against the hardware i2c-interface.

(gpio-i2c driver:  https://github.com/zephyrproject-rtos/zephyr/issues/27855 )

Best Regards, Jonas 

[Michal]

Hello Jonas,

Thank you for the information. I will mark the ticket as closed then.
In case of any other questions, please open a new ticket.

Best regards,

Michal