Another issue with nRF52840 and MCUBoot - not starting without RTT and stopping when it is disconnected

[Paskin]

Hello, 

I went through couple of a posts like nRF52840 custom board won't boot without debugger "kick" start and tried to apply suggested solutions - without much luck.

Got a custom board, based on nRF52840 rev.3 (everything explained below is tested on 2 instances). Please find below the clock and power schematic.
 

I am trying to run the Blinky sample, compiled for nrf52840dk_nrf52840 target (with the only overlay for a LED, which is connected to P1.00) - and flash it via SWD cable using PCA10040 v.1.1.1 board as JLink adapter and TC2030 cable. My device runs from a battery - and recognised by developer tools (this is why I used an adapter with the different chip - to see if I am talking to the right one). 

The issue - with a default configuration my board not being reset after the flashing and cannot power up autonomously - it requires RTT to be connected to run. When RTT disconnected - the LED stops blinking, but if I just physically disconnect the cable w/o disconnectiing the viewer programmatically - it continues to work. I did some search in DevZone and applied the configuration CONFIG_BOARD_ENABLE_DCDC=n. It fixed the situation - now my board runs straight away after flashing, as well as when battery is pulled out and connected again. 

But when I enable MCUboot with CONFIG_BOOTLOADER_MCUBOOT=y - it reverts the situation to an above explained state, application doesn't run until RTT viewer is connected. 
I am using 2.4.1 Connect SDK and JLink 7,88j along with nrfjprog 10.23.2

Please advise

[Kazi Afroza Sultana]

Helo,

Some project configurations can be overwritten by child images. That's why, enabling mcuboot may be the cause of not running the program on board.

Can you post your prj.conf for your project + configurations for your custom boards?

Thanks.

BR

Kazi

[Paskin]

Thanks, it indeed was a reason.

If the board requires DCDC to be disabled - it has to be disabled in a board, not the project configuration. 

[sean]

Hi，

    I have encountered the same problem and need the RTT connection ，code to run 。Disconnect RTT, code stops running，may be what's the problem? 

[Paskin]

I managed to solve it by setting CONFIG_DC_DC (not sure for exact spelling) to "n". But to be taken into an account, it has to be done in the board definition, not the application config.

[sean]

This operation is possible, but I would like to inquire nordic what may be cause this happen