J-Link Debugger Hang Issue

[brushlow]

I am developing on a custom board nRF5340 using an external J-Link Base Classic in VSCode nRF Connect SDK 2.0.0. I am using macOS 13.4.1. After months of being able to debug without issue, I now am having issues getting the debugger to work. Flashing always works fine, and the application runs as expected. When selecting Debug, the terminal indicates everything has loaded successfully and I see the Debug bar in VSCode, but main() breakpoint is never hit and the Debug bar shows a pause button as if it is running. Trying to hit the pause button does nothing. Here is the Debug Console output:

JLinkGDBServerCLexe: SEGGER J-Link GDB Server V7.88m Command Line Version
JLinkGDBServerCLexe: 
JLinkGDBServerCLexe: JLinkARM.dll V7.88m (DLL compiled Jul 19 2023 14:21:54)
JLinkGDBServerCLexe: 
JLinkGDBServerCLexe: -----GDB Server start settings-----
JLinkGDBServerCLexe: GDBInit file:                  none
JLinkGDBServerCLexe: GDB Server Listening port:     64727
JLinkGDBServerCLexe: SWO raw output listening port: 2332
JLinkGDBServerCLexe: Terminal I/O port:             2333
JLinkGDBServerCLexe: Accept remote connection:      yes
JLinkGDBServerCLexe: Generate logfile:              off
JLinkGDBServerCLexe: Verify download:               off
JLinkGDBServerCLexe: Init regs on start:            off
JLinkGDBServerCLexe: Silent mode:                   on
JLinkGDBServerCLexe: Single run mode:               on
JLinkGDBServerCLexe: Target connection timeout:     0 ms
JLinkGDBServerCLexe: ------J-Link related settings------
JLinkGDBServerCLexe: J-Link Host interface:         USB
JLinkGDBServerCLexe: J-Link script:                 none
JLinkGDBServerCLexe: J-Link settings file:          none
JLinkGDBServerCLexe: ------Target related settings------
JLinkGDBServerCLexe: Target device:                 nRF5340_xxAA_APP
JLinkGDBServerCLexe: Target device parameters:      none
JLinkGDBServerCLexe: Target interface:              SWD
JLinkGDBServerCLexe: Target interface speed:        12000kHz
JLinkGDBServerCLexe: Target endian:                 little
JLinkGDBServerCLexe: 
=thread-group-added,id="i1"
=cmd-param-changed,param="pagination",value="off"
arch_cpu_idle () at /opt/nordic/ncs/v2.0.0/zephyr/arch/arm/core/aarch32/cpu_idle.S:105
105		cpsie	i
[New Remote target]

The IDE will sit like this indefinitely. That is, until I found that by merely opening up the nRF Connect for Desktop Programmer application, the main() breakpoint is immediately hit. At that point, I am able to step and set breakpoints as expected. The Debug Console output is amended with the following:

[New Thread 536893792]
[New Thread 536890440]
[New Thread 536894288]
[New Thread 536887536]
[New Thread 536887784]
[Switching to Thread 536894040]

Thread 2 hit Breakpoint 1, main () at ../src/main.c:201
201	{

This is okay as a workaround, but I'm eager to find a long-term solution as to why this occurs. I've tried deleting my Segger tools installation and re-installing (the universal version, as per the Nordic installation guide), and upgraded the probe firmware using JLinkConfig, to no avail. I also have a nRF5340 DK, and I do NOT experience the same issue debugging when using the on-board debugger; I tried using the external J-Link probe on the DK (instead of the on-board debugger), and I DO encounter the debugging issue. So it appears localized to either the external J-link probe or its interaction with my PC.

Thanks in advance for any insights!

[JONATHAN LL]

Thanks for the clarification. I think we are on the same page then. I have been checking with the developers on this but currently still many is on vacation, so it will be looked at but can promise any traction on the matter. Might be hard to preproduce as well.
Feel free to update if you find some other solution or if the issue is suddenly fixed. Will also keep you updated if i find anything else useful to ask about or if there is something else the developers would like to know. 

Regards,
Jonathan 

[brushlow]

Understood, I know it's a strange issue.

I guess to summarize based on what I've seen and what you've had me try, it seems like there is an issue with the interaction between specifically the J-Link Base probe and GDB within the nRF Connect environment (given that Ozone works well).

Can the devs suggest anything in particular to uninstall and reinstall that might be the problem area? I have tried to uninstall and reinstall the J-Link package.

[JONATHAN LL]

Will keep you updated when I have any news. 

[brushlow]

I believe I've figured out the issue, though I'm not sure how it arose to begin with. I noticed in Ozone that the Target Interface Speed was set to 4MHz, where everything worked perfectly. nRF Debug was setting the speed to 12MHz by default. In my launch.json file, I added a serverArgs parameter to my debug config using the external J-Link and changed the speed from 12000 to 4000. Everything seems to work now.