RE: nRF54L15 and RTT

Igor — Mon, 15 Dec 2025 14:53:37 GMT

Works on NCS 3.2.0

RE: nRF54L15 and RTT

Vidar Berg — Wed, 26 Nov 2025 10:49:28 GMT

I see. This requirement looks to have been removed in SDK v3.1.0 by the following commits:

- https://github.com/nrfconnect/sdk-zephyr/commit/13054293adb045d51762a8dd5b60612dd60e475c

- https://github.com/nrfconnect/sdk-zephyr/commit/77925656ab8

RE: nRF54L15 and RTT

Igor — Wed, 26 Nov 2025 10:29:54 GMT

It turns out that CONFIG_USERSPACE=y was the offending line. Is there any way to use RTT in combination with CONFIG_USERSPACE or not?

RE: nRF54L15 and RTT

Vidar Berg — Wed, 26 Nov 2025 06:39:25 GMT

From the warning message I can see it's failing because CONFIG_USERSPACE or CONFIG_LOG_MODE_MINIMAL is enabled in your configuration. For logging, the default is CONFIG_LOG_MODE_DEFERRED, but note that CONFIG_NCS_SAMPLES_DEFAULTS will select log mode minimal if you have this enabled in your project configuration.

RE: nRF54L15 and RTT

Igor — Tue, 25 Nov 2025 13:55:34 GMT

The following settings do not compile

CONFIG_LOG=y
CONFIG_LOG_BACKEND_RTT=y
CONFIG_LOG_BUFFER_SIZE=8192
CONFIG_USE_SEGGER_RTT=y
CONFIG_RTT_CONSOLE=y
CONFIG_UART_CONSOLE=n

Error is:


warning: LOG_PRINTK (defined at subsys/logging\Kconfig.processing:8) has direct dependencies !USERSPACE && !LOG_MODE_MINIMAL && LOG with value n, but is currently being y-selected by the following sym
bols:
 - LOG_BACKEND_RTT_FORCE_PRINTK (defined at subsys/logging\backends\Kconfig.rtt:103), with value y, direct dependencies LOG_BACKEND_RTT && !LOG_FRONTEND_ONLY && !LOG_MODE_MINIMAL && LOG (value: y), an
d select condition LOG_BACKEND_RTT && !LOG_FRONTEND_ONLY && !LOG_MODE_MINIMAL && LOG (value: y)Parsing C:/ncs/v3.0.2/zephyr/Kconfig


error: Aborting due to Kconfig warnings
Loaded configuration 'C:/ncs/v3.0.2/zephyr/boards/nordic/nrf54l15dk/nrf54l15dk_nrf54l15_cpuapp_ns_defconfig'
Merged configuration 'H:/cup/prj.conf'
Merged configuration 'H:/cup/build/cup/zephyr/.config.sysbuild'

CMake Error at C:/ncs/v3.0.2/zephyr/cmake/modules/kconfig.cmake:396 (message):
  command failed with return code: 1
Call Stack (most recent call first):
  C:/ncs/v3.0.2/nrf/cmake/modules/kconfig.cmake:36 (include)
  C:/ncs/v3.0.2/zephyr/cmake/modules/zephyr_default.cmake:133 (include)
  C:/ncs/v3.0.2/zephyr/share/zephyr-package/cmake/ZephyrConfig.cmake:66 (include)
  C:/ncs/v3.0.2/zephyr/share/zephyr-package/cmake/ZephyrConfig.cmake:92 (include_boilerplate)
  CMakeLists.txt:4 (find_package)


-- Configuring incomplete, errors occurred!
CMake Error at cmake/modules/sysbuild_extensions.cmake:514 (message):
  CMake configure failed for Zephyr project: cup

  Location: H:/cup
Call Stack (most recent call first):
  cmake/modules/sysbuild_images.cmake:43 (ExternalZephyrProject_Cmake)
  cmake/modules/sysbuild_default.cmake:21 (include)
  C:/ncs/v3.0.2/zephyr/share/zephyr-package/cmake/ZephyrConfig.cmake:75 (include)
  C:/ncs/v3.0.2/zephyr/share/zephyr-package/cmake/ZephyrConfig.cmake:92 (include_boilerplate)
  C:/ncs/v3.0.2/zephyr/share/sysbuild-package/cmake/SysbuildConfig.cmake:8 (include)
  template/CMakeLists.txt:10 (find_package)


-- Configuring incomplete, errors occurred!
See also "H:/cup/build/CMakeFiles/CMakeOutput.log".
←[91mFATAL ERROR: command exited with status 1: 'C:\ncs\toolchains\0b393f9e1b\opt\bin\cmake.EXE' -DWEST_PYTHON=C:/ncs/toolchains/0b393f9e1b/opt/bin/python.exe '-Bh:\cup\build' -GNinja -DBOARD=nrf54l15
dk/nrf54l15/cpuapp/ns '-SC:\ncs\v3.0.2\zephyr\share\sysbuild' '-DAPP_DIR:PATH=h:\cup'
←[0m

The following settings work with logging to COM port:

CONFIG_LOG=y
CONFIG_LOG_BUFFER_SIZE=8192

I did not try without MCUboot.

Any idea how to fix RTT logging?

Note:
NCS 3.0.2, LOG_xxx().
printk() is not used.

RE: nRF54L15 and RTT

Vidar Berg — Tue, 25 Nov 2025 12:56:40 GMT

Hello,

Do you have CONFIG_LOG and CONFIG_LOG_BACKEND_RTT enabled as well? Also, did you have RTT logging working before including MCUBoot?

Best regards,

Vidar