nRF54L15 RTT

[garrettb]

Hi

When running a project on the nRF54L15 using nRF Connect in VS Code, I often cannot connect to RTT.
I select RTT in nRF Connect, but no output appears.
If I retry multiple times (e.g., re-flashing the device, occasionally resetting, or restarting VS Code), I can eventually get RTT to connect. Once it connects successfully, it tends to work reliably for a while.
When RTT fails to connect, each attempt triggers a pop-up from SEGGER J-Link (v8.66) asking me to select the Manufacturer and Device. This adds extra delay each time.
The behavior is inconsistent: sometimes RTT works immediately, other times it requires several attempts before it stabilizes.

Could there be a setting in my project that is missing, or is this known behaviour?

Thanks

[alfonsocole]

This does not look like a missing application setting only. There is a known issue around RTT on nRF54L15 where the VS Code RTT terminal may start J-Link with the target name NRF54L15_xxAA, while SEGGER J-Link expects the device to be selected as nRF54L15_M33.

That is why the SEGGER dialog appears and asks for Manufacturer/Geometry Dash Subezero. When nRF54L15_M33 is selected manually, RTT usually starts working.

I would still check that RTT logging is enabled in the project configuration, for example:

CONFIG_LOG=y
CONFIG_USE_SEGGER_RTT=y
CONFIG_LOG_BACKEND_RTT=y
CONFIG_RTT_CONSOLE=y

And if you want to use RTT only instead of UART console:

CONFIG_UART_CONSOLE=n
CONFIG_SERIAL=n

However, based on the behavior you described, especially the repeated J-Link device-selection popup, the main issue is most likely tool/device selection related rather than your application not printing logs