Hello,

I am having some troubles with my J-Link BASE debugger. I am trying to use it as part of an automatic test suite, where I use the J-Link BASE to program a Nordic nRF52 board prior to running some tests. In this test suite, the J-Link BASE is used multiple times to re-program the board and get an SWO connection for debug logs.

This typically works well the first few times, but after initiating and closing the connection a couple times, it stops working. Instead, I get this error with every attempt:


I can restore the J-Link by unplugging and replugging it. However, that is not much of a solution, since I need this to be automated.

I have J-Link Software Pack 6.30e installed, with the debugger firmware updated. I'm using Windows 10. I have tried using both jlink.exe solely and arm-none-eabi-gdb + jlinkgdbservercl.exe in my scripts, and have the same problem.

Do you have any idea of what causes this, and a way to avoid the problem? Or do you know some better way to restore the J-Link than replugging its USB cable?

Best regards,
Fabian

Hello,

I am using J-Link to download software and get debug logs as part of a test automation system in Robot Framework/Python. As such, I have a Python script which in turn starts J-Link and other applications. I have tried two approaches, both which give me the same error.

For the first approach, Python starts J-Link Commander with the following command:

Source Code

1. jlink -device nRF52832_xxAA -If SWD -Speed 4000 -autoconnect 1 -commanderscript {commander_script_path}

The commander script contains the following commands:

Source Code

1. h
2. loadfile {binary_path}
3. r
4. go
5. swoview {swo_freq}

The command is started using Python's subprocess.Popen(), and the process is killed when the test suite is finished.

For the other approach I use arm-none-eabi-gdb + J-Link GDB Server CL + Telnet. Here, I first start J-Link GDB Server CL with the following command:

Source Code

1. JLinkGDBServerCL -select USB -device {cpu_type} -if SWD -speed 1000 -ir -singlerun -vd -strict -nogui -timeout 0

I then start arm-none-eabi-gdb with the following command:

Source Code

1. arm-none-eabi-gdb --eval-command='set $swo_cpu_speed = {swo_cpu_speed}' --eval-command='set $should_run = {should_run}' --command={gdb_commands_path} {binary_path}

The GDB commands file contains this:

Source Code

1. set mem inaccessible-by-default off
3. target remote localhost:2331
5. monitor speed 1000
6. monitor clrbp
7. monitor reset
8. monitor halt
9. monitor regs
10. flushreg
12. monitor speed auto
13. monitor flash breakpoints 1
15. monitor semihosting enable
16. monitor semihosting IOClient 1
18. monitor SWO DisableTarget 0xFFFFFFFF
19. eval "monitor SWO EnableTarget %u 0 0x1 0", $swo_cpu_speed
21. load
23. monitor clrbp
24. monitor reset
25. monitor halt
26. monitor regs
27. flushreg
29. if $should_run
30. continue
31. else
32. quit
33. end

Display All

These processes are also started using Python's subprocess.Popen(). Finally, I start Telnet using Python's telnetlib. When the test suite is over, I kill the processes using process.kill().

Perhaps the process killing in Python is not nice enough to close J-Link properly?

Do you think there is a better way to do this? I have not really looked into the SDK. Is it easy to achieve what I want through Python using the SDK?

I have run my script with the second approach adding a '-log' parameter to the GDB Server command. I'm attaching the log outputs: both from a successful attempt and from a subsequent failed attempt.

(I omitted some lines from the successful attempt's log, since I guessed that they were actually the binary I'm downloading... Perhaps I'm overly paranoid, but I prefer to be on the safe side.)

Thank you very much for taking your time to help me!

Best regards,
Fabian

Hello,

Thank you very much for your help. I have now found a solution.

I have realized that there is no easy way to gracefully terminate a subprocess in Python in Windows. It is possible, but it would require a bunch of extra wrapping code. If anyone is interested to learn more, check this link.

Instead, I did as you recommended, and used the SDK. Well, I didn't use the SDK directly, but I found the excellent Python library pylink, which in turn uses the SDK. The pylink library allows me to easily close the J-Link connection in a graceful manner.

Best regards,
Fabian