Unable to flash custom board[NRF54L05] using NRF54L15 DK

RE: Unable to flash custom board[NRF54L05] using NRF54L15 DK

NithinAG — Wed, 25 Feb 2026 08:28:51 GMT

okay

RE: Unable to flash custom board[NRF54L05] using NRF54L15 DK

SwRa — Mon, 23 Feb 2026 13:17:23 GMT

Hi Nithin,

Please open a private ticket here in Devzone and share the schematics that needs to reviewed.

Regards,

Swathy

RE: Unable to flash custom board[NRF54L05] using NRF54L15 DK

NithinAG — Sat, 21 Feb 2026 06:44:51 GMT

Okay. I'll try with shorter wires as well. I have been able to get 5cm SWD FRC cable.

PFA, the layout. Would like to get it verified.

Regards,

Nithin

RE: Unable to flash custom board[NRF54L05] using NRF54L15 DK

SwRa — Thu, 19 Feb 2026 10:38:38 GMT

Hi Nithin,

It should be the wire length as discussed in the thread.. Have you connected SWD0_SELECT to GND on the external board.? Just to verify, have you gotten the hardware layouts verified by our team here.?

Regards,

Swathy

RE: Unable to flash custom board[NRF54L05] using NRF54L15 DK

NithinAG — Thu, 19 Feb 2026 04:52:00 GMT

Hi,

Thanks for the info. Looks like i have got the board up and running.

But, when i try to flash I get this error:

Device error: Setting the debug port SELECT register failed while powering up sys and debug regions (Unknown Error in J-Link DLL (error code =-1)).

Simliar to the error described in the theard you have linked for the length of the wire. Is this due to the wire length? ot is this something else?

Haven been unable to find a shorternwire here. I'll try to find one and try.

RE: Unable to flash custom board[NRF54L05] using NRF54L15 DK

SwRa — Wed, 18 Feb 2026 14:34:45 GMT

Hi Nithin,

The following are the connections that needeed:

Pin 1: SWD0_VTG → target VDD (or used to power the target)
Pin 2: SWD0_SWDIO → target SWDIO
Pin 3: SWD0_SELECT → must be tied to GND on the external board
Pin 4: SWD0_SWDCLK → target SWDCLK
Pin 5: GND → target GND
Pin 10: SWD0_RESET → target RESET (optional but recommended)

Refer: https://docs.nordicsemi.com/bundle/ug_nrf54l15_dk/page/UG/nRF54L15_DK/program_debug/debug_out_ext_board.html

It seems that you have missed out the SWD0_SELECT. If SWD0_SELECT is left floating or high, the onboard debugger will keep talking to the DK’s own nRF54L15 instead of your external nRF54L05.

Also, for the nRF54L15 DK there is a known issue with the level shifters: It is recommended to use cables no longer than ~8–10 cm since longer cables can cause the external target not to be detected or give J‑Link errors. See this ticket: nRF54L DK can't program external MCU via SWD – J-Link error (Unknown Error in DLL)

Best Regards,

Swathy