nRF9160DK (nrf9160dk_nrf52840) – Missing Kconfig symbols & logging failure when building BLE app on the nRF52840 core

[ayboo]

Hi Nordic Team,

I’m working with the nRF9160DK, specifically targeting the nRF52840 application core (nrf9160dk_nrf52840).

While building a BLE Central application on the 52840 core using NCS v3.1.0, the build fails due to several missing Kconfig symbols and RTT logging issues

• RTT backend works on the nRF9160 core,

  but RTT has no output on the nRF52840 core unless debug options are carefully tuned.

• BT debug configs behave differently than on standard nRF52840 boards.

• Multiple UART/RTT interfaces appear when connecting the DK, making it unclear

  which interface belongs to the nRF52840 core.

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 What I Need Clarification On

1. Which Kconfig symbols are expected to be supported on the nRF52840 application core?

   Are BT_GATT_NOTIFY, BT_GATT_READ, etc. intentionally removed?

2. Is there an official list of supported/pruned features for the nrf9160dk_nrf52840 core?

3. How should RTT logging be configured properly for the 52840 core on this board?

4. What is the recommended way to get runtime logs from the 52840 MCU when both cores (nRF9160 + nRF52840) are active?

• Board: nRF9160DK

• Target: nrf9160dk_nrf52840

• NCS Version: 3.1.0

• Build System: west + CMake

• Host: macOS

I can provide:

• prj.conf

• Builder logs

• RTT Viewer screenshots

• The exact logs from J-Link RTT and Zephyr console

Thanks in advance for your support!

It seems like the 52840 core on the DK may be using a pared-down configuration, and I’d like to confirm which features are officially supported or expected to be missing.

ım kinda new on this so can you guys please explain step by step.

[Hakon]

Hello,

can you include the build logs, code and kconfig files?

Also, you can try using RTT logging on a basic Zephyr sample like blinky.

[ayboo]

Hi, thanks for the quick response.

I found the root cause of the issue.

The excessive log output was not coming from my application — it was generated by several default Zephyr and controller subsystems. Because the log level was too high (default DEBUG in some modules), my own application logs were being flooded and pushed out of the terminal buffer.

After disabling unnecessary logging modules and lowering global log levels in my Kconfig (prj.conf), everything started working correctly.

My own logs now appear normally both when acting as Central and when the phone connects simultaneously.

So the issue was not related to UART, RTT, or hardware — it was purely due to overly verbose subsystem logs masking the application output.

Thanks for the support.

[Hakon]

Good stuff.