origin: https://mcuoneclipse.com/2015/03/20/attaching-to-a-running-target-with-segger-j-link-gdb-and-eclipse/

This happens several times for me: I have a board running for a while (even for days), and then it crashes or is stuck somewhere. Yes, I usually use a watchdog do recover from that situation. But it would be good to know and debug the problem. With CodeWarrior I had the functionality in the debugger to ‘attach’ or ‘connect’ to a running (stuck/crashed) board. However, with Eclipse/Kinetis Design Studio/GDB this is a different debugger, and not possible. At connection time with the debugger the target does a reset, so I don’t know any more where the application crashed. But now I have a solution, at least with the Segger GDB :-).

Outline

I’m using here Kinetis Design Studio V2.0.0, but it is applicable to any Eclipse with the GNU ARM Eclipse plugins and the Segger GDB Server (e.g. with J-Link debug probe or J-Link OpenSDA firmware). The goal is to be able to connect to a running target, without overwriting the application on the board (attach/connect) so the problem on the board can be inspected with the GNU GDB debugger. That means the GDB connection shall *not* reset the target as it usually does.

Update GNU ARM Eclipse Segger Debug Plugin

Verify that you have the latest GNU ARM Eclipse plugins installed. In Eclipse/KDS, use the menu Help > Install New Software and use the following update site:

http://gnuarmeclipse.sourceforge.net/updates

I had to update the GNU ARM C/C++ J-Link Debugging plugins to the version 3.1.2.201502281154 (see above screenshot).

Segger J-Link Debug Panel

This update comes with an important feature: the ‘Connect to running target’ option is now available (it was grayed out and not functional in earlier versions).

Debugging and Attach

I enable the option ‘Connect to running target’ and I’m able to attach/connect to my target. Use debug as normally, the target will be shown as running), then use the ‘Pause’/Suspend button to stop the target if the target is still running:

I’m able to successfully attach and debug to my boards with the J-Link (EDU). I’m able to connect the J-Link (EDU) after the crash and to attach/debug it. Using the J-Link ‘Light’ version I had at least to Power the J-Link “Lite” before attaching it to the board, otherwise the board was reset by connecting the SWD/JTAG cable. I recommend you get some practice and experience hooking up the probe. Or (if you can) keep the debug probe powered/attached so you do not risk an accidental reset of the board.

Summary

With the new update and plugin I’m able to debug a crashed application and can connect to the board after the crash to find out what the status of the board is. Thanks to Liviu (the maintainer of the GNU ARM Eclipse plugins) and Segger to make this important feature work with GDB :-).