Using the nRF secure immutable bootloader to update the application core

[Ryisen]

Hi everyone,

I'm using an nRF 5340-DK and want to update the application core firmware by using the nRF secure immutable bootloader. The bootloader and the network core do not need to be updated.

I used the example project "central_bas" where I added the bootloader by adding "CONFIG_SECURE_BOOT=y" to the prj.conf file. The bootloader works as it gives the expected output to a e.g. Putty console.

Now what I don't unterstand is how to send application firmware images to the bootloader in order to update the application core. I couldn't find any examples in the official nRF Connect SDK documentation. For this I am using nRF Connect SDK v1.9.0.

For testing I tried to program the application core with nrfjprog, but it would give me an error saying that "readback protection" is enabled and I have to flash the complete application core.

What I try to achieve is to send new firmware images to the bootloader, which updates the current firmware on the application core.

Best regards,

Alex

[Ryisen]

I found the option of "CONFIG_BUILD_S1_VARIANT=y", but CMake throws an error if I add this to the prj.conf file.

How can I build for S1 as the target?

[Ryisen]

It says "BOARD is not being defined on the CMake command-line in the environment or by the app."