Ee(42) Could not connect to core

[dhruvgangadwala]

I am using the LPC55S06-EVK board and encountering the following error when trying to connect via MCUXpresso IDE.

The board was previously working fine with the same setup — I was able to load and debug code successfully. However, without any changes to the hardware or toolchain, the connection suddenly stopped working and started giving this error.

Executing flash operation 'Erase' (Erase flash) - Fri May 30 14:33:49 IST 2025
Checking MCU info...
Scanning for targets...
Executing flash action...
LinkServer RedlinkMulti Driver v24.12 (Dec 18 2024 18:40:01 - crt_emu_cm_redlink build 869)
( 0) Reading remote configuration
Wc(03). No cache support.
Found chip XML file in /home/dhruv/Documents/MCUXpresso_24.12.148/workspace/lpcxpresso55s06_led_blinky_lpc_blink/Debug/LPC55S06.xml
( 5) Remote configuration complete
Reconnected to existing LinkServer process.
Connecting to probe 1 core 0 (using server started externally) reports:
'Ee(42). Could not connect to core.'
Retrying...
Reconnected to existing LinkServer process.
Server OK but no connection to probe 1 core 0 (after 3 attempts) - Ee(42). Could not connect to core.
Failed on connect: Ee(42). Could not connect to core.
No connection to chip's debug port
(100) Target Operation Failed
Unable to perform operation!
Command failed with exit code 1

[Alice_Yang]

Hello @dhruvgangadwala 

The first thing to try to recover debug access is to boot into the ISP bootloader. This is normally controlled by the state of ISP pin(s) as the MCU comes out of reset.

1. Press and hold the ISP button.

2. Whilst still holding down the ISP button, press and release the RST button.

3. Release the ISP button.

4. Then using Flash Magic or other tools masse erase flash.
5. Reset board.
6. Create a new MCUXpresso IDE workspace, import SDK demo, debug again.

Detail you can also refer to:

https://community.nxp.com/t5/LPCXpresso-IDE-FAQs/Regaining-debug-access-to-target-MCU/m-p/473923  

BR

Alice