softdevice controller example code?

[protobits]

I'm looking into integrating the SoftDevice controller (not full SoftDevice) from nrfxlib into NuttX RTOS. NuttX would already provide the host layer so I would only need to use the HCI interface for integration. However, the documentation for SDC looks very superficial (brief description and full API, but not many details) and I cannot find example code to see some particular aspects of integration. Is there somewhere I can see some example code using this?

I'm not really sure if I need to initialize the MPSL before SDC or if the SDC already does this on its own. Also, I'm not entirely sure how the interrupt handling is done behind the scenes (mpsl appears to expect an interrupt number during initialization but SDC does not). Also, how does this interact with other high priority interrupts and SVC handler set up by RTOS? Should they all be lower priority or is it OK to have everything maximum priority (as NuttX normally does)?

Final question: I see many answers in this forum regarding a "controller only SoftDevice with HCI interface" with "Nordic does not provide this". Is it that SDC is newer? Or is it somehow not official/fully supported?

[Kenneth]

It should be possible to use the softdevice controller with other RTOS than zephyr, but not something I have tried. Hopefully these pages can give some guidance:

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrfxlib/softdevice_controller/README.html

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrfxlib/softdevice_controller/doc/softdevice_controller.html 

[protobits]

Yes, I've read this documentation. But there's no example code and it is a bit superficial.

I understand that Zephyr uses its own open-source controller. Or is there zephyr code which uses the SDC that I can look? (I looked but couldn't find anything)

[Kenneth]

Try:

1. Sample code from Zephyr (NCS) that uses the controller: https://github.com/nrfconnect/sdk-nrf/blob/master/subsys/bluetooth/controller/hci_driver.c
2. Note: you'll need to initialize MPSL as well https://github.com/nrfconnect/sdk-nrf/blob/master/subsys/mpsl/mpsl_init.c

[protobits]

Thanks, I just found out this code as well. It is quite useful.

My only remaining question is about interrupt priorities (as I don't see in that code how these are handled): if my RTOS uses interrupts (and, particularly SVcall exceptions for context switches), do these need to be lower priority? Or is it OK to have everything same priority?

[Kenneth]

There is some MPSL documentation explaining the expected interrupt configuration: Integration notes — nrfxlib 1.4.99 documentation (nordicsemi.com). The SoftDevice controller documents its requirements related to thread safety: Integration with applications — nrfxlib 1.4.99 documentation (nordicsemi.com). If there is something that can be improved, let us know.