OpenOCD debugging not working on boards with new flash protector

[Yury Morgunov]

Hi all!
I have several pca10056 boards, some of which are quite old with a serial number < 1000000000. There are boards with higher serial numbers that come with factory-installed flash memory protection. On these new boards, debugging through openocd does not work. When connecting, openocd displays the error message "Error: No J-Link device found." This does not depend on whether I specify the serial number in the config or not. Here is an example of my config:

telnet_port 50002
gdb_port 50000

adapter driver jlink
adapter serial 1050232322
adapter speed 5000
transport select swd

command to start openocd:

openocd -f jlink_test_cfg.cfg 

If I change the adapter serial to 683681827, everything works. As a result, debugging only works on 3 old boards, it doesn't work on a bunch of new boards, I tried on all of them :). I remember for sure that it used to work for me, maybe the issue is with the firmware for J-Link. I also tried using an older version of OpenOCD (0.10.0), but the problem remained the same.

I'm currently using Openocd 0.12.0.
Version jlink SEGGER J-Link Commander V7.92c (Compiled Aug 30 2023 14:58:04).

Is it possible to try old firmware for JLink? If anyone has a similar problem, how did you solve it? I am using OpenOCD because I am unable to attach to the already running board using the J-Link GDB server in VSCode.

[Turbo J]

Do the J-link devices show up in dmesg or in "lsusb" at all?

The J-Link GDB server can attach to running code with the "-noir -nohalt" command line parameters.

[Yury Morgunov]

I got to the point where I started using openocd. Here is the command to start the server.

JLinkGDBServer -singlerun -nogui -if swd -port 50000 -swoport 50001 -telnetport 50002 -device nrf52840_xxaa -select usb=1050232322 -rtos GDBServer/RTOSPlugin_FreeRTOS.so -speed 1000 -noir -nohalt

Everything works, everything starts, but there is one important problem. FreeRTOS streams are not readable.
Manual requests for thread or stack information:

info threads
  Id   Target Id         Frame 
  2    Remote target     0x00025f40 in ?? ()

The current thread <Thread ID 
1> has terminated.  See `help thread'.
{"output":"","token":37,"outOfBandRecord":[],"resultRecords":{"resultClass":"done","results":[]}}

bt
The current thread has terminated
The current thread has terminated (from interpreter-exec console "bt")

I can only get this information if I continue executing the code and immediately pause it. Then everything starts to work, but this is not what is needed.

[New Thread 537086184]
[New Thread 537084752]
[New Thread 537088640]
[New Thread 537097944]
[New Thread 537095784]
[New Thread 537091976]
[New Thread 537069128]
[New Thread 537078200]

Thread 
3 received signal SIGTRAP, Trace/breakpoint trap.
[Switching to Thread 537086184]
0x0006f3c0 in nrfx_coredep_delay_us::delay_machine_code ()

I don't have enough understanding of the debugging process to do anything with this.

[Susheel Nuguru]

Which application are you running on the board? Is it a BLE based application using the softdevice? If so, then you cannot pause and run the application.

You might have to use Monitor mode debugging to be able to do that 

[Yury Morgunov]

Yes, I am using the application with softdevice. The goal is to completely stop the processor and see the current state. I don't need to step through the code. In general, openocd did an excellent job with this task.

Is Monitor mode debugging available under license on pca10056?

[Susheel Nuguru]

Yury Morgunov said:

Is Monitor mode debugging available under license on pca10056?

I think that the J-Link OB that is included on the DKs does not include a license for monitor mode debugging. On Windows machines, the J-Link driver will allow evaluation of the monitor mode debugging feature if the user accepts a license pop-up. 

Yury Morgunov said:

The goal is to completely stop the processor and see the current state

That should not be a problem with any debugger, but we do not test this and I do not think we support OpenOCD with NCS but it looks like Zephyr does.