Handling resets with HCI SPI

[Abraham Hamidi]

For nrf52x, a pin can be dedicated for reset, and this is from my understanding how HCI works in the sample (host line to controller reset pin). However, for the nrf5340, there is no RESET pin possible for the network core from what I've researched. Since the HCI SPI driver requires reset gpio pin(s), what is the best way to get it working between the application and network core on the 5340? Can I customize the driver to use FORCEOFF, or does that require UART (the network core only allows using one of SPI or UART)?

I need SPI specifically. I know UART is an option and seems to be prepared, but I am using the NRF5340 development kit to test for another similar device that requires SPI for this purpose.

[Øivind]

Hi,

At first glance it looks like using FORCEOFF instead of the reset pin should work. I will ask the developers and get back to you.

[Abraham Hamidi]

Thanks. It will probably work now that I see it's a shared register, but I'll wait for a response. If that is the case, then I will make a PR to sdk-nrf that checks if CPUNET is enabled. By the way, since ENABLE_CPUNET is required to release FORCEOFF, how can I make that not allocate gpio for UART, since I'm not using UART? I think right now all that can be done is to disable serial and hope the generate stubs don't interfere with anything. I might patch that code to check CONFIG_SERIAL.

[Øivind]

I've spoken to a developer and I believe modifying the hci spi driver to use NETWORK.FORCEOFF instead should work.

You can disable uart in the devicetree using an overlay file.
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.0.0/zephyr/build/dts/howtos.html

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.0.0/zephyr/build/dts/intro.html#dt-input-files