Custom board with nRF5340: after reset firmware does not run and SWD is locked

[denis]

I'm using ncs 3.2.1 with a custom board (Holyiot-20046-v1.0).  I used the "Create a new board" function in nRF Connect VSCODE to create the board file.  I copied the Zephyr Blinky sample and added an alias for led0.  All builds and run from the debugger.  However, if I power cycle the board the firmware does not run and SWD is locked.

What is the correct procedure to setup the build so that the firmware does run and SWD is not locked?

Also, how can I set a breakpoint before the firmware is run so that I can debug the startup sequence and see why SWD is not being unlocked?

Additional Info:

I have tried using sys build explicitly with the following in sysbuild.conf:

SB_CONFIG_NETCORE_EMPTY=y

That does build a net app and I can flash them both, but it still seems to have the same issue of firmware not running and SWD is locked.

[Hung Bui]

Hi Dennis, 
From what showed in the schematic of the module, there is an inductor on DCCH pin. So it's quite strange that setting regulator-initial-mode to LDO changed the behavior. 

Do you have a 2nd board that you can test with ? Just in case it's an issue with one single board. 

If you have a nRF5340 DK , can you compile an application for the custom board and flash on the DK, do you see the same problem ? I think this should reveal if it's the issue with the hardware on the board or it's the firmware configuration. 

If you don't have a DK, have you tried to flash an application built for a DK to the custom board ? From what I can see you should be a able to run a default application for the DK on the module as it  has both the crystals, and DCDC enabled.