LPC1778 can't connect after programming by JLINK

BianHaopeng1 — Thu, 04 Jun 2026 01:55:34 GMT

Hello! After programming the LPC1778 chip with a J-Link debugger, the target chip cannot be connected. This same fault has happened on two distinct circuit boards in my possession.

I confirm the issue is not caused by the programmed application code. The data I programmed is full-chip random values, and programming the exact same random dataset using a different programming tool does not produce this connectivity issue.

The initial connection and programming process complete normally without any error alerts. After power cycling the board post-programming, all communication with the hardware fails. The connection log is listed below:

Connecting ...
- Connecting via USB to probe/ programmer device 0
- Probe/ Programmer firmware: J-Link V9 compiled May 7 2021 16:26:12
- Probe/ Programmer S/N: 69401860
- Device "LPC1778" selected.
- Target interface speed: 4000 kHz (Fixed)
- VTarget = 3.283V
- Failed to attach to CPU. Trying connect under reset.
- ERROR: Failed to connect.
Could not establish a connection to target.
General troubleshooting guide: https://kb.segger.com/J-Link_Troubleshooting
- ERROR: Connect failed

Addtionally, I capture waveforms with a logic analyzer, the DP port of the SWD interface works normally, whereas all AP accesses result in ACK FAULT responses.

Re: LPC1778 can't connect after programming by JLINK

Alice_Yang — Thu, 04 Jun 2026 04:07:53 GMT

Hello @BianHaopeng1

Please first download and run a simple “Hello World” project on your board, rather than using random values, and then test whether debugging works properly.

If debugging still does not work, please check your schematic design by referring to the LPCXpresso board for LPC1769 with CMSIS DAP probe | NXP Semiconductors

If the issue still persists, please feel free to contact me.

Alice

topic Re: LPC1778 can't connect after programming by JLINK in LPC Microcontrollers

LPC1778 can't connect after programming by JLINK

Re: LPC1778 can't connect after programming by JLINK