nRF52840 DK (PCA10056; 3.0.3; 2024.36) not responding over J-Link, detected as nRF534

[Sai]

Hi Nordic team,

I recently purchased a new nRF52840 DK with the following label information:

• PCA10056

• Hardware Version: 3.0.3

• 2024.36

• 1050218770

I attempted to flash the blinky example using VS Code with nRF Connect SDK v2.5.2 and Toolchain v2.7.0. The SEGGER J-Link version is v7.94e.

However, during flashing, the DK suddenly became unresponsive over the onboard J-Link interface. I then attempted to recover and flash it using an external J-Link debugger, but encountered the following error:

Failed to read device memories.
[error] [  nRF52] - Device memory generation failed.
[error] [ Worker] - Detected CPU core "235012351" does not match expected CPU core "234881279"

here is the 

Fullscreen log_nrf52840.log Download

[2025-Jul-30 15:44:42] [debug] --------------------------------------------------------------------------------
[2025-Jul-30 15:44:42] [debug] C:\Program Files\Nordic Semiconductor\nrf-command-line-tools\bin\nrfjprog.exe --program c:\Users\SBandaru\my_projects\Connected_IoT\Projects\blinky\build\zephyr\zephyr.hex --sectoranduicrerase --verify -f NRF52 --snr 822002154 --log 
[2025-Jul-30 15:44:42] [debug] nrfjprog version 10.24.2 external
[2025-Jul-30 15:44:42] [debug] --------------------------------------------------------------------------------
[2025-Jul-30 15:44:42] [ info] Load library at C:\Program Files\Nordic Semiconductor\nrf-command-line-tools\bin\nrfjprog.dll.
[2025-Jul-30 15:44:42] [ info] Library loaded, loading member functions.
[2025-Jul-30 15:44:42] [ info] Member functions succesfully loaded.
[2025-Jul-30 15:44:42] [debug] [ Client] - open
[2025-Jul-30 15:44:42] [debug] [ Client] - start
[2025-Jul-30 15:44:42] [ info] [ Client] - stdout: Jlinkarm nRF Worker ready. Handling sequence 36b6a62f-1d11-4941-9e93-04ad254dc502.

[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - Logger sink registered in Segger backend logger
[2025-Jul-30 15:44:42] [debug] [  JLink] - Logger sink registered in JLink logger
[2025-Jul-30 15:44:42] [debug] [  nRF52] - open
[2025-Jul-30 15:44:42] [debug] [  nRF52] - just_check_family
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - open_dll
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - No J-Link DLL path was provided. Attempting to auto detect.
[2025-Jul-30 15:44:42] [ info] [SeggerBackend] - Load library at C:\Program Files\SEGGER\JLink_V794e\JLink_x64.dll.
[2025-Jul-30 15:44:42] [ info] [SeggerBackend] - Library loaded, loading member functions.
[2025-Jul-30 15:44:42] [ info] [SeggerBackend] - Member functions succesfully loaded.
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - Set batch mode
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - dll_version
[2025-Jul-30 15:44:42] [ info] [SeggerBackend] - Segger dll version 7.94.e loaded.
[2025-Jul-30 15:44:42] [trace] [ Worker] - Command open executed for 6 milliseconds with result 0
[2025-Jul-30 15:44:42] [trace] [ Client] - Command open executed for 78 milliseconds with result 0
[2025-Jul-30 15:44:42] [debug] [ Client] - config
[2025-Jul-30 15:44:42] [trace] [ Client] - Command config executed for 15 milliseconds with result 0
[2025-Jul-30 15:44:42] [debug] [ Client] - enum_emu_snr
[2025-Jul-30 15:44:42] [debug] [  nRF52] - config
[2025-Jul-30 15:44:42] [trace] [ Client] - Command enum_emu_con_info executed for 15 milliseconds with result 0
[2025-Jul-30 15:44:42] [debug] [ Client] - connect_to_emu_with_snr
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - enum_emu_snr
[2025-Jul-30 15:44:42] [trace] [ Worker] - Command config executed for 3 milliseconds with result 0
[2025-Jul-30 15:44:42] [debug] [  nRF52] - enum_emu_con_info
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - is_connected_to_emu
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - enum_emu_con_info
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - is_connected_to_emu
[2025-Jul-30 15:44:42] [trace] [ Worker] - Command enum_emu_con_info executed for 4 milliseconds with result 0
[2025-Jul-30 15:44:42] [debug] [  nRF52] - connect_to_emu_with_snr
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - is_connected_to_emu
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - connect_to_emu_with_snr
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - is_connected_to_emu
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_enum_emu_snr
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_get_num_emus
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_connect_to_emu_with_snr
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_connect_to_emu_without_snr
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - Segger logging enabled.
[2025-Jul-30 15:44:42] [trace] [  JLink] - Firmware: J-Link V12 compiled Feb 20 2025 16:24:27
[2025-Jul-30 15:44:42] [trace] [  JLink] - Firmware: J-Link V12 compiled Feb 20 2025 16:24:27
[2025-Jul-30 15:44:42] [trace] [  JLink] - Hardware: V12.00
[2025-Jul-30 15:44:42] [trace] [  JLink] - S/N: 822002154
[2025-Jul-30 15:44:42] [trace] [  JLink] - OEM: SEGGER
[2025-Jul-30 15:44:42] [trace] [  JLink] - Feature(s): GDB
[2025-Jul-30 15:44:42] [trace] [  JLink] - Bootloader: 2022 Oct 19
[2025-Jul-30 15:44:42] [trace] [  JLink] - USB speed mode: High speed (480 MBit/s)
[2025-Jul-30 15:44:42] [trace] [  JLink] - TELNET listener socket opened on port 19021
[2025-Jul-30 15:44:42] [trace] [  JLink] - WEBSRV WEBSRV_Init(): Starting webserver thread(s)
[2025-Jul-30 15:44:42] [trace] [  JLink] - WEBSRV Webserver running on local port 19080
[2025-Jul-30 15:44:42] [trace] [  JLink] - Looking for J-Link GUI Server exe at: C:\Program Files\SEGGER\JLink_V794e\JLinkGUIServer.exe 
[2025-Jul-30 15:44:42] [trace] [  JLink] - Forking J-Link GUI Server: C:\Program Files\SEGGER\JLink_V794e\JLinkGUIServer.exe 
[2025-Jul-30 15:44:42] [trace] [  JLink] - J-Link GUI Server info: "J-Link GUI server V7.94e " 
[2025-Jul-30 15:44:42] [trace] [ Client] - Command connect_to_emu_with_snr executed for 111 milliseconds with result 0
[2025-Jul-30 15:44:42] [debug] [ Client] - read_connected_emu_snr
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 81.198ms returns "O.K."  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_Lock()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_ExecCommand("SetRestartOnClose = 0", ...).   
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.001ms returns 0x01  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_ExecCommand("DisableFlashDL", ...).   
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.000ms returns 0x00  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_ExecCommand("ExcludeFlashCacheRange 0x0-0xFFFFFFFF", ...).   
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.005ms returns 0x00  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_SetHookUnsecureDialog  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_SetHookUnsecureDialog(...)
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.011ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_TIF_Select(JLINKARM_TIF_SWD)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 2.041ms returns 0x00  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_GetSpeedInfo()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - 180000000 Hz / n, n >= 12
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.009ms  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - Connected emulator supports SWD speeds up to 15000kHz
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_SetSpeed(2000)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.242ms  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_GetSpeed()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.005ms returns 2000  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - SWD clock set to 2000kHz
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_GetSN()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.004ms returns 822002154  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.004ms  
[2025-Jul-30 15:44:42] [debug] [  nRF52] - read_device_family
[2025-Jul-30 15:44:42] [trace] [ Worker] - Command connect_to_emu_with_snr executed for 105 milliseconds with result 0
[2025-Jul-30 15:44:42] [trace] [ Client] - Command read_connected_emu_snr executed for 15 milliseconds with result 0
[2025-Jul-30 15:44:42] [debug] [ Client] - read_device_info
[2025-Jul-30 15:44:42] [debug] [  nRF52] - read_connected_emu_snr
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - is_connected_to_emu
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_IsOpen()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.020ms returns 0x01  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_Lock()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - read_connected_emu_snr
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.004ms  
[2025-Jul-30 15:44:42] [trace] [ Worker] - Command read_connected_emu_snr executed for 0 milliseconds with result 0
[2025-Jul-30 15:44:42] [error] [ Client] - Encountered error -5: Command read_device_info executed for 16 milliseconds with result -5
[2025-Jul-30 15:44:42] [warning] Failed to read device info. Attempting to complete command anyways.
[2025-Jul-30 15:44:42] [debug] [  nRF52] - read_device_info
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - is_connected_to_emu
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_IsOpen()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.011ms returns 0x01  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_Lock()  
[2025-Jul-30 15:44:42] [debug] [  nRF52] - Just_read_device_version
[2025-Jul-30 15:44:42] [debug] [  nRF52] - Just_readback_status
[2025-Jul-30 15:44:42] [debug] [  nRF52] - Just_is_ctrl_ap_available
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - coresight_configure
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_GetHWStatus(...)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.492ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_Configure()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.756ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - read_debug_port_idr
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - read_debug_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_read_debug_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_select_debug_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - Select AP 255, DP Bank 0, AP Bank 255
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_WriteAPDPReg(DP reg 0x02, 0x00000000)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.246ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_ReadAPDPReg(DP reg 0x00)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - Value=0x6BA02477
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.211ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.062ms  
[2025-Jul-30 15:44:42] [error] [ Worker] - Encountered unexpected debug port ID 6, expected 2
[2025-Jul-30 15:44:42] [trace] [ Worker] - Command read_device_info executed for 1 milliseconds with result -5
[2025-Jul-30 15:44:42] [debug] [ Client] - read_memory_descriptors
[2025-Jul-30 15:44:42] [debug] [  nRF52] - read_memory_descriptors
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - is_connected_to_emu
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_IsOpen()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.007ms returns 0x01  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_Lock()  
[2025-Jul-30 15:44:42] [debug] [  nRF52] - Just_read_memory_descriptors
[2025-Jul-30 15:44:42] [debug] [  nRF52] - Just_readback_status
[2025-Jul-30 15:44:42] [debug] [  nRF52] - Just_is_ctrl_ap_available
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_is_debug_region_powered
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_read_debug_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_select_debug_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - Select AP 255, DP Bank 0, AP Bank 255
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_WriteAPDPReg(DP reg 0x02, 0x00000000)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.713ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_ReadAPDPReg(DP reg 0x01)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - Value=0xF0000040
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.940ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_select_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - Select AP 1, DP Bank 0, AP Bank 15
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_WriteAPDPReg(DP reg 0x02, 0x010000F0)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 2.645ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_ReadAPDPReg(AP reg 0x03)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - Value=0x84770001
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 2.829ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_select_access_port_register
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_ReadAPDPReg(AP reg 0x03)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - Value=0x84770001
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 1.071ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_select_access_port_register
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_ReadAPDPReg(AP reg 0x03)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - Value=0x84770001
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.651ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_select_access_port_register
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_ReadAPDPReg(AP reg 0x03)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - Value=0x84770001
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 2.060ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [  nRF52] - update_device_memory_list
[2025-Jul-30 15:44:42] [debug] [  nRF52] - Just_read_device_version
[2025-Jul-30 15:44:42] [debug] [  nRF52] - Just_readback_status
[2025-Jul-30 15:44:42] [debug] [  nRF52] - Just_is_ctrl_ap_available
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_select_access_port_register
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_ReadAPDPReg(AP reg 0x03)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - Value=0x84770001
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 1.906ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_select_access_port_register
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_ReadAPDPReg(AP reg 0x03)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - Value=0x84770001
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.520ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_select_access_port_register
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_ReadAPDPReg(AP reg 0x03)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - Value=0x84770001
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.496ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_read_access_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_select_access_port_register
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_ReadAPDPReg(AP reg 0x03)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - Value=0x84770001
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.493ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - read_u32
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_connect_to_device
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - is_connected_to_device
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_IsConnected()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.004ms returns FALSE  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---set_coresight_ahb_ap_index
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_ExecCommand("CORESIGHT_SetIndexAHBAPToUse = 0", ...).   
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.001ms returns 0x00  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_ExecCommand("device = nRF52", ...).   
[2025-Jul-30 15:44:42] [trace] [  JLink] - Device "NRF52" selected.
[2025-Jul-30 15:44:42] [trace] [  JLink] - Device "NRF52" selected.
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 1.074ms returns 0x00  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_Connect()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - InitTarget() start
[2025-Jul-30 15:44:42] [trace] [  JLink] - InitTarget() start
[2025-Jul-30 15:44:42] [trace] [  JLink] -  J-Link Script File: Executing InitTarget() 
[2025-Jul-30 15:44:42] [trace] [  JLink] - InitTarget() end - Took 4.70ms
[2025-Jul-30 15:44:42] [trace] [  JLink] - InitTarget() end - Took 4.70ms
[2025-Jul-30 15:44:42] [trace] [  JLink] - Found SW-DP with ID 0x6BA02477
[2025-Jul-30 15:44:42] [trace] [  JLink] - Found SW-DP with ID 0x6BA02477
[2025-Jul-30 15:44:42] [trace] [  JLink] - DPIDR: 0x6BA02477
[2025-Jul-30 15:44:42] [trace] [  JLink] - DPIDR: 0x6BA02477
[2025-Jul-30 15:44:42] [trace] [  JLink] - CoreSight SoC-400 or earlier
[2025-Jul-30 15:44:42] [trace] [  JLink] - CoreSight SoC-400 or earlier
[2025-Jul-30 15:44:42] [trace] [  JLink] - AP map detection skipped. Manually configured AP map found.
[2025-Jul-30 15:44:42] [trace] [  JLink] - AP map detection skipped. Manually configured AP map found.
[2025-Jul-30 15:44:42] [trace] [  JLink] - AP[0]: AHB-AP (IDR: Not set)
[2025-Jul-30 15:44:42] [trace] [  JLink] - AP[0]: AHB-AP (IDR: Not set)
[2025-Jul-30 15:44:42] [trace] [  JLink] - AP[0]: Core found
[2025-Jul-30 15:44:42] [trace] [  JLink] - AP[0]: Core found
[2025-Jul-30 15:44:42] [trace] [  JLink] - AP[0]: AHB-AP ROM base: 0xE00FE000
[2025-Jul-30 15:44:42] [trace] [  JLink] - AP[0]: AHB-AP ROM base: 0xE00FE000
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPUID register: 0x410FD214. Implementer code: 0x41 (ARM)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPUID register: 0x410FD214. Implementer code: 0x41 (ARM)
[2025-Jul-30 15:44:42] [trace] [  JLink] - Feature set: Mainline
[2025-Jul-30 15:44:42] [trace] [  JLink] - Feature set: Mainline
[2025-Jul-30 15:44:42] [trace] [  JLink] - Cache: No cache
[2025-Jul-30 15:44:42] [trace] [  JLink] - Cache: No cache
[2025-Jul-30 15:44:42] [trace] [  JLink] - Found Cortex-M33 r0p4, Little endian.
[2025-Jul-30 15:44:42] [trace] [  JLink] - Found Cortex-M33 r0p4, Little endian.
[2025-Jul-30 15:44:42] [trace] [  JLink] - Identified core does not match configuration. (Found: Cortex-M33, Configured: Cortex-M4)
[2025-Jul-30 15:44:42] [trace] [  JLink] -    ***** Warning: 
[2025-Jul-30 15:44:42] [trace] [  JLink] - Identified core does not match configuration. (Found: Cortex-M33, Configured: Cortex-M4)
[2025-Jul-30 15:44:42] [trace] [  JLink] - -- Max. mem block: 0x000054B8
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE000EDF0)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0002000)
[2025-Jul-30 15:44:42] [trace] [  JLink] - FPUnit: 8 code (BP) slots and 0 literal slots
[2025-Jul-30 15:44:42] [trace] [  JLink] - FPUnit: 8 code (BP) slots and 0 literal slots
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE000EDFC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_WriteMem(4 bytes @ 0xE000EDFC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0001000)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0001000)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0001028)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0001038)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0001048)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0001058)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_WriteMem(4 bytes @ 0xE0001000)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE000ED88)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_WriteMem(4 bytes @ 0xE000ED88)
[2025-Jul-30 15:44:42] [error] [ Client] - Encountered error -5: Command read_memory_descriptors executed for 59 milliseconds with result -5
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE000ED88)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_WriteMem(4 bytes @ 0xE000ED88)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE000EFB8)
[2025-Jul-30 15:44:42] [trace] [  JLink] - Security extension: implemented
[2025-Jul-30 15:44:42] [trace] [  JLink] - Security extension: implemented
[2025-Jul-30 15:44:42] [trace] [  JLink] - Secure debug: enabled
[2025-Jul-30 15:44:42] [trace] [  JLink] - Secure debug: enabled
[2025-Jul-30 15:44:42] [trace] [  JLink] - CoreSight components:
[2025-Jul-30 15:44:42] [trace] [  JLink] - CoreSight components:
[2025-Jul-30 15:44:42] [trace] [  JLink] - ROMTbl[0] @ E00FE000
[2025-Jul-30 15:44:42] [trace] [  JLink] - ROMTbl[0] @ E00FE000
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(64 bytes @ 0xE00FE000)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(32 bytes @ 0xE00FFFE0)
[2025-Jul-30 15:44:42] [trace] [  JLink] - [0][0]: E00FF000 CID B105100D PID 000BB4C9 ROM Table
[2025-Jul-30 15:44:42] [trace] [  JLink] - [0][0]: E00FF000 CID B105100D PID 000BB4C9 ROM Table
[2025-Jul-30 15:44:42] [trace] [  JLink] - ROMTbl[1] @ E00FF000
[2025-Jul-30 15:44:42] [trace] [  JLink] - ROMTbl[1] @ E00FF000
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(64 bytes @ 0xE00FF000)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(32 bytes @ 0xE000EFE0)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE000EFBC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE000EFCC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - [1][0]: E000E000 CID B105900D PID 000BBD21 DEVARCH 47702A04 DEVTYPE 00 Cortex-M33
[2025-Jul-30 15:44:42] [trace] [  JLink] - [1][0]: E000E000 CID B105900D PID 000BBD21 DEVARCH 47702A04 DEVTYPE 00 Cortex-M33
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(32 bytes @ 0xE0001FE0)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0001FBC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0001FCC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - [1][1]: E0001000 CID B105900D PID 000BBD21 DEVARCH 47701A02 DEVTYPE 00 DWT
[2025-Jul-30 15:44:42] [trace] [  JLink] - [1][1]: E0001000 CID B105900D PID 000BBD21 DEVARCH 47701A02 DEVTYPE 00 DWT
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(32 bytes @ 0xE0002FE0)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0002FBC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0002FCC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - [1][2]: E0002000 CID B105900D PID 000BBD21 DEVARCH 47701A03 DEVTYPE 00 FPB
[2025-Jul-30 15:44:42] [trace] [  JLink] - [1][2]: E0002000 CID B105900D PID 000BBD21 DEVARCH 47701A03 DEVTYPE 00 FPB
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(32 bytes @ 0xE0000FE0)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0000FBC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0000FCC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - [1][3]: E0000000 CID B105900D PID 000BBD21 DEVARCH 47701A01 DEVTYPE 43 ITM
[2025-Jul-30 15:44:42] [trace] [  JLink] - [1][3]: E0000000 CID B105900D PID 000BBD21 DEVARCH 47701A01 DEVTYPE 43 ITM
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(32 bytes @ 0xE0041FE0)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0041FBC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0041FCC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - [1][5]: E0041000 CID B105900D PID 002BBD21 DEVARCH 47724A13 DEVTYPE 13 ETM
[2025-Jul-30 15:44:42] [trace] [  JLink] - [1][5]: E0041000 CID B105900D PID 002BBD21 DEVARCH 47724A13 DEVTYPE 13 ETM
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(32 bytes @ 0xE0042FE0)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0042FBC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0042FCC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - [1][6]: E0042000 CID B105900D PID 000BBD21 DEVARCH 47701A14 DEVTYPE 14 CSS600-CTI
[2025-Jul-30 15:44:42] [trace] [  JLink] - [1][6]: E0042000 CID B105900D PID 000BBD21 DEVARCH 47701A14 DEVTYPE 14 CSS600-CTI
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(32 bytes @ 0xE0040FE0)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0040FBC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_ReadMem(4 bytes @ 0xE0040FCC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - [0][1]: E0040000 CID B105900D PID 000BBD21 DEVARCH 00000000 DEVTYPE 11 TPIU
[2025-Jul-30 15:44:42] [trace] [  JLink] - [0][1]: E0040000 CID B105900D PID 000BBD21 DEVARCH 00000000 DEVTYPE 11 TPIU
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 39.293ms returns 0x00  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORE_GetFound()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.004ms returns 0xE0200FF  
[2025-Jul-30 15:44:42] [error] [  nRF52] - Device memory generation failed.
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.093ms  
[2025-Jul-30 15:44:42] [error] [ Worker] - Detected CPU core "235012351" does match expected CPU core "234881279"
[2025-Jul-30 15:44:42] [trace] [ Worker] - Command read_memory_descriptors executed for 55 milliseconds with result -5
[2025-Jul-30 15:44:42] [debug] [  nRF52] - close
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - is_connected_to_emu
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_IsOpen()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.010ms returns 0x01  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_Lock()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - close
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - disconnect_from_emu
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_disconnect_from_emu
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - is_connected_to_device
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_IsConnected()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.002ms returns TRUE  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_is_debug_region_powered
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_read_debug_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_select_debug_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - Select AP 255, DP Bank 0, AP Bank 255
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_WriteAPDPReg(DP reg 0x02, 0x00000000)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.205ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_ReadAPDPReg(DP reg 0x01)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - Value=0xF0000040
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.360ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - Disable trace before closing connection.
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_write_u32
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_write_debug_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_select_debug_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - Select AP 255, DP Bank 0, AP Bank 255
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_WriteAPDPReg(DP reg 0x02, 0x00000000)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.241ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_WriteAPDPReg(DP reg 0x02, 0x00000000)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.159ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_WriteU32_64(0xE000EDFC, 0x00000000)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - Debug reg: DEMCR
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU is running
[2025-Jul-30 15:44:42] [trace] [  JLink] - CPU_WriteMem(4 bytes @ 0xE000EDFC)
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.727ms returns 0 (0x00000000)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_is_debug_region_powered
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - Shortcut, lock is on and debug region is powered.
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - unpower_debug_and_system_regions
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_write_debug_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_select_debug_port_register
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_WriteAPDPReg(DP reg 0x01, 0x00000000)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.324ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_is_debug_region_powered
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_read_debug_port_register
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - ---just_select_debug_port_register
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_CORESIGHT_ReadAPDPReg(DP reg 0x01)  
[2025-Jul-30 15:44:42] [trace] [  JLink] - Value=0x00000040
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.283ms returns 0  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_HasError()  
[2025-Jul-30 15:44:42] [trace] [  JLink] - - 0.005ms  
[2025-Jul-30 15:44:42] [trace] [  JLink] - JLINK_Close()  
[2025-Jul-30 15:44:42] [debug] [SeggerBackend] - Segger Backend closed.
[2025-Jul-30 15:44:42] [debug] [  nRF52] - nRF family DLL closed
[2025-Jul-30 15:44:42] [trace] [ Client] - Command close executed for 61 milliseconds with result 0
[2025-Jul-30 15:44:42] [debug] [ Client] - terminate
[2025-Jul-30 15:44:42] [trace] [ Worker] - Command close executed for 45 milliseconds with result 0
[2025-Jul-30 15:44:42] [trace] [ Client] - Command terminate executed for 0 milliseconds with result 0
[2025-Jul-30 15:44:42] [trace] [ Worker] - Command terminate executed for 0 milliseconds with result 0
[2025-Jul-30 15:44:42] [trace] [ Worker] - Executed 9 commands for 219 milliseconds
[2025-Jul-30 15:44:42] [debug] [ Client] - Worker process exited with code: 0
[2025-Jul-30 15:44:42] [debug] [ Client] - Worker process exited with code: 0
[2025-Jul-30 15:44:42] [debug] [ Client] - Child process terminated with result 0
[2025-Jul-30 15:44:42] [trace] [ Client] - Executed 9 commands for 370 milliseconds
[2025-Jul-30 15:44:42] [debug] [ Client] - terminate

When trying to connect using J-Link tools, the detected CPU is reported as: NRF5340_xxAA_APP & Device Version: NRF5340_xxAA_REV1

As a test, I also built the blinky project for nRF5340 and successfully flashed it, but the LED does not blink. Here is the 0336.log_nrf5340.log

Current Behavior:

• The board is no longer detected correctly as an nRF52840 DK.

• J-Link tools report it as an nRF5340 device.

• Flashing any nRF52840-targeted code fails with CPU core mismatch.

• Flashing nRF5340 code succeeds, but doesn’t behave correctly (LED doesn’t blink).

• Unable to use the onboard J-Link

Steps Taken So Far:

1. Tried flashing via VS Code + nRF Connect SDK.

2. Attempted recovery using external J-Link.

3. Tried building/flashing code for nRF5340.

4. Verified power and USB connections.

Questions:

• Could this be a misprogrammed or misidentified chip on the DK?

• Is there a way to hard recover or reflash the correct bootloader/firmware for the nRF52840 DK?

• Could the board have been mislabeled during manufacturing?

Any help to restore this DK to a working nRF52840 state would be greatly appreciated.

Thanks in advance!

[PaKa]

Can you attach a picture of the kit and note where you plugged your external debugger in?

[Sai]

Hi Paka,

Here is the picture

[PaKa]

That is the programming header for the On Board Debugger/SEGGER device, this is indeed a nRF5340.

If you erased that device then the board can't be recovered and the debug and UART to USB bridge is lost forever. You will still be able to program the nRF52840 if you instead use the debug in connector, this is the 20 pin footprint just below where you hooked up. This will require you to solder a 10 pin header to this connector, 20 pin header if you want the TRACE feature instead.

For future reference, any specific reason for selecting the approach you used to try to recover the board? Want to make sure more people don't try this.

[Sai]

Thanks for the clarification. In my case, I actually didn’t perform any recovery procedure or attempt to erase the chip. However, the on-board J-Link has stopped responding regardless. I'm unsure what might have caused this, which is why I tried external J-Link

Do you happen to have a .hex or .bin image that could be used to restore the debug and UART-to-USB bridge functionality on the board? That might help bring it back to life, if it's still salvageable. Appreciate any guidance you can offer on this.

[PaKa]

So when you programmed the blinky project you did erase the Debugger chip on the board and then the debugger is gone. There is no way to recover the board unfortunately, it's non-salvageable.