Using NCS as Zephyr Support for STM32

[Benjamin]

Using NCS 2.1.2 and it's accompanying Zephyr version, we have a few boards we are building for. Some are based around the nRF9160/nRF52840 and some are around STM32 devices. This has been fine until I just tried enabling MCUBOOT as the bootloader for the STM32 devices. NCS is trying to enable several NRF defines once I enable CONFIG_BOOTLOADER_MCUBOOT=y I don't see that it should select anything that is Nordic specific, but there must be some dependencies that are being enabled? It has all kinds of build issues at that point since it is an STM32 chip but is now being treated partially as a Nordic chip. Any ideas how to fix this other than build it outside of the NCS? Or is that my only option?

[Amanda Hsieh]

Hi, 

Our NCS support is based on Nordic chips, so I would let the question open to other experts.  

Regards,
Amanda H.

[Benjamin]

The NCS allows the building of other chips based around Zephyr, like the STM32. It should be something as simple as a CMake check that the target board has a Nordic device or not whether any of the "nrf" or "nrfxlib" is included. Or does Nordic not guarantee that any of the other Zephyr supported boards/mcu's will build because it always tries to include Nordic cmake files when it shouldn't? I am able to build for a custom STM32 board, until I include CONFIG_BOOTLOADER_MCUBOOT, then a bunch of Nordic unique stuff gets pulled in, but fails, because the rest of Zephyr is only looking for STM32 related files.

[Amanda Hsieh]

Hi, 

The Zephyr of NCS is imported from vanilla Zephyr and slightly modified for our Nordic chips and application requirements. Since we assume our users are using Nordic chips, we don't test and restrict other chips. However, that doesn't mean they are supported. If you have any zephyr issues with other chips than Nordic, please contact Zephyr Discord. 

Regards,
Amanda H.

[Benjamin]

After chatting in the Zephyr Discord, I was shown that the nRF Connect SDK license explicitly states: 

4. This software, with or without modification, must only be used with a
   Nordic Semiconductor ASA integrated circuit.

Which can be found here: https://github.com/nrfconnect/sdk-nrf/blob/d026c5db57da421048c6b86c9c6920332275606e/LICENSE

So, the solution is to have two west workspaces, one for the NCS and one for vanilla Zephyr.