nRF54L DK can't program external MCU via SWD – J-Link error (Unknown Error in DLL)

[Doris.chen]

Hello Nordic Team,

I’m trying to use the nRF54L DK to program an external MCU via SWD, but I’m encountering an error during connection. I’ve already followed this guide:

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

However, I’m still unable to connect to the external target via nRF Connect for Desktop – Programmer.

Here is the error log I get:

18:14:44.589	Error: Failed with exit code 1. Failed to device info one or more devices:
  * 1057763412: [Probe] Device error: Failed to write DebugPort register 2: Unknown Error in J-Link DLL (error code = -1)
  Message: Operation device-info failed
18:14:44.590	Using nrfutil device to communicate with target via JLink
18:14:45.728	Reading readback protection status for Application core
18:14:45.729	Failed "reading readback protection status for application core". 
  Error: code: 1, description: Generic, message: Batch task protection-get failed
18:14:45.892	Error: Failed with exit code 1. One or more batch tasks failed
  - [Probe] Device error: Failed to write DebugPort register 2: Unknown Error in J-Link DLL (error code = -1)

Interestingly, with the same external target, I’m able to successfully program it using an nRF54L PDK (another board), so I don’t think the issue is with the target itself.

1. Are there any extra jumpers, settings required on the nRF54L DK to enable external MCU programming?

2. Is there a known limitation when using nRF Connect Programmer with the nRF54L DK’s onboard debugger?

3. Do I need to use nrfjprog or nrfutil manually instead of the GUI?

Any help or suggestions would be appreciated.

Thank you very much!

Best regards,
Doris

[runsiv]

Hi

1. There should not be needed anything different

2. Not that i'm aware

3. You need to use nrfutil, nrfjprog is deprecated ref Important: The nRF Command Line Tools have been archived and replaced by nRF Util. No further updates will be made to the nRF Command Line Tools. Last supported operating systems are Windows 10, Linux Ubuntu 22.04, and macOS 13. The nRF Command Line Tools will remain available for download, but do not install the SEGGER J-Link version they provide if you have a newer version installed.

I suspect in your case the voltage on the target device and the DK is to big for the DK to program the device. I would recommend either using the 10 pin flat cable or using board configuration in nRF Connect for desktop and adjust the voltage closer to that of the current voltage. 

Regards

Runar

[Doris.chen]

Hi Runar,

Thank you for your reply!

Regarding this part of your message:

---

"I suspect in your case the voltage on the target device and the DK is too big for the DK to program the device."

---

I'm not quite sure I fully understand what you meant. Could you please clarify what “too big” refers to?

Are you referring to a voltage mismatch between the target device's supply voltage and the VTG on the nRF54L DK, which defines the I/O levels for the SWD interface?

To clarify, here is my current setup:

1. The target device is powered by an external 3.3 V power supply.

2. I have configured the nRF54L DK's VDD (nPM VOUT1) to output 3.3 V using the Board Configurator tool in nRF Connect for Desktop.

3. I am connecting to the external target via the 10-pin SWD header on the DK, with SWDIO, SWDCLK, GND, and VTG all properly connected.

4. With this setup, the nRF54L DK is not able to detect the target at all (an error is shown in Programmer).
   Interestingly, when I use an nRF52 DK with the same external 3.3 V target setup, the target can be detected successfully, although flashing is not possible — which is expected.

Could you provide more technical details on what kind of voltage mismatch might prevent the nRF54L DK from connecting to the target?

Thanks again for your support.

Best regards,
Doris

[runsiv]

Hi

Please write it in English. I guess just from the image it might have worked on a 52dk and not on the 54?

Regards

Runar

[Sai]

I am facing the same problem. I can confirm that it works with a 52DK while it doesn't work with the 54DK. I created a separate ticket.