PCA10056 rev 3.0.3 (2026.7) - J-Link OB nRF5340 stuck in bootloader, firmware update always fails

[AMC0]

Hi 

Brand new nRF52840-DK (PCA10056 rev 3.0.3, serial 1050245467, sticker on PCB). Never worked.

J-Link OB firmware update fails every time with: "Sending firmware data... OK (1019904 bytes). Waiting for emulator to attach... Timeout. Emulator did not re-enumerate."

Tested on macOS (Apple Silicon) AND Windows 10 with same result. Tried J-Link V7.94e, V9.24a, V9.32, nRF Connect Programmer v4.7.3, Board Configurator v1.1.5, nrfutil 8.1.1 recover — all fail.

nrfutil device list sees the board (traits: devkit, jlink, seggerUsb) but nrfutil device recover returns "No emulator found".

Tried 3 cables, multiple USB ports, holding RESET while plugging. Current firmware shows "May 18 2021 BTL" (bootloader only).

Is there a recovery procedure for nRF5340 OB on rev 3.0.3, or is this a factory defect?

thank you

[Menon]

Hello,

Could you please try running the command nrfutil device x-update-debug-probe-firmware? This updates the firmware on the SEGGER J-Link debug probe present on the DK. Please check whether this resolves the issue.

If that does not help, please open J-Link Commander and run the connect command, as this may also recover the device.

Kind Regards,

Abhijith

[AMC0]

Hi Abhijith,

Both suggestions failed:

1) nrfutil device x-update-debug-probe-firmware --serial-number 1050245467
Result: "Emulator error: No emulator with connection info 'Usb(JLinkSerialNumber(1050245467))' was found"

2) JLinkExe → connect after firmware update failure:
Result: The firmware update fails first ("Communication timed out, Emulator did not re-enumerate"), then the connect command returns "J-Link connection not established yet but required for command. Connecting to J-Link via USB...FAILED: Cannot connect to J-Link."

The J-Link OB is completely unreachable after every firmware update attempt. The firmware data is always sent successfully (1019904 bytes OK), the emulator detaches, but it never re-enumerates on USB. This happens on both macOS (Apple Silicon) and Windows 10 with J-Link V9.24a and V9.32.

I believe this is a factory defect. My distributor (Mouser) is already sending a replacement unit. Is there anything else I can try, or can you confirm this board is defective?

Thank you,
François

[Menon]

Hello,

If neither of those options updates the debug firmware, then I do not think there is a way to recover the device.

AMC0 said:

I believe this is a factory defect. My distributor (Mouser) is already sending a replacement unit. Is there anything else I can try, or can you confirm this board is defective?

It is good to hear that you are receiving a replacement. Usually, this does not happen, and I am not entirely sure what might have caused the issue in this case.

Please let me know once you receive the new DK and confirm that everything is working as expected.

Kind Regards,

Abhijith