Behavior of SW_CTRL0 on NRF7001

[Nils Ruf]

Hello,

We are currently developing a Zephyr-based connectivity solution using the NRF5340 alongside an NRF7001 WiFi chip.
Since we also want to use Bluetooth we have implemented a shared antenna setup and want to control an antenna switch with the NRF7001's SW_CTRL0 pin.

Reading the NRF7001's product specification I found this section stating that the behavior of SW_CTRL0/1 is programmable and dependent on the coexistence mode.

However, I could not find any information on how this works exactly. I just saw the schematics of the NRF7002DK and looked at the antenna switch (see below).

So here are my questions:

• What is the default behavior of the SW_CTRL0 pin? In the image above it looks like the NRF7002 is setting SW_CTRL0 high whenever it wants to send.
• Can this behavior be changed?
• Is there any Nordic-specific setup of the coexistence interface I have to do in Zephyr?

Thank you very much in advance.

Kind regards,

Nils

[Priyanka]

Hi Nils,

What is the default behavior of the SW_CTRL0 pin? In the image above it looks like the NRF7002 is setting SW_CTRL0 high whenever it wants to send.

The SW_CTRL0 pin behaves like an output control signal that is set high when the nRF7002 needs to switch to the WiFi antenna, usually when it is transmitting. This is in order to control an external antenna switch (like the one in the schematic) so that the correct radio (WiFi or Bluetooth) has access to the antenna at any given time.

Can this behavior be changed?

Yes, this behaviour is programmable : https://docs.nordicsemi.com/bundle/ps_nrf7002/page/chapters/functional/doc/coexistence.html#:~:text=The%20behavior%20of%20SW_CTRL0/1%20is%20programmable%20and%20dependent%20on%20the%20configured%20coexistence%20mode%20and%20switch%20control%20interface. 

Is there any Nordic-specific setup of the coexistence interface I have to do in Zephyr?

Zephyr has support for WiFi and Bluetooth coexistence through the 3-wire or 4-wire coexistence interface (typically SW_CTRL0 and SW_CTRL1 for antenna switching). Nordic provides coexistence drivers in the nRF Connect SDK that helps manage this. You need to define the correct coexistence mode in your device tree and configure the coexistence settings for the nRF7002 within the WiFi driver.

-Priyanka