Debugging Zephyr app on reel board with GDB TUI see some python error.

[smrtos]

Host environment:

• Ubuntu: 20.04.3 LTS (Focal Fossa)
• Python: 3.8.10
• PyOCD: 0.32.0
• Zephyr SDK: 0.13.1

Steps:

• Build zephyr blinky sample application cmake -B build -S samples/basic/blinky -GNinja -DBOARD=reel_board cd build ninja

• Start gdbserver: pyocd gdbserver --target=nrf52840 --frequency=4000000 Output:

    0000275:INFO:board:Target type is nrf52840
    0000321:INFO:dap:DP IDR = 0x2ba01477 (v1 rev2)
    0000337:INFO:ap:AHB-AP#0 IDR = 0x24770011 (AHB-AP var1 rev2)
    0000394:INFO:ap:AP#1 IDR = 0x02880000 (AP var0 rev0)
    0000396:INFO:target_nRF52:NRF52840 not in secure state
    0000406:INFO:rom_table:AHB-AP#0 Class 0x1 ROM table #0 @ 0xe00ff000 (designer=244 part=008)
    0000412:INFO:rom_table:[0]<e000e000:SCS v7-M class=14 designer=43b part=00c>
    0000416:INFO:rom_table:[1]<e0001000:DWT v7-M class=14 designer=43b part=002>
    0000420:INFO:rom_table:[2]<e0002000:FPB v7-M class=14 designer=43b part=003>
    0000424:INFO:rom_table:[3]<e0000000:ITM v7-M class=14 designer=43b part=001>
    0000428:INFO:rom_table:[4]<e0040000:TPIU M4 class=9 designer=43b part=9a1 devtype=11 archid=0000 devid=ca1:0:0>
    0000432:INFO:rom_table:[5]<e0041000:ETM M4 class=9 designer=43b part=925 devtype=13 archid=0000 devid=0:0:0>
    0000434:INFO:cortex_m:CPU core #0 is Cortex-M4 r0p1
    0000442:INFO:cortex_m:FPU present: FPv4-SP-D16-M
    0000446:INFO:dwt:4 hardware watchpoints
    0000448:INFO:fpb:6 hardware breakpoints, 4 literal comparators
    0000463:INFO:server:Semihost server started on port 4444 (core 0)
    0000472:INFO:gdbserver:GDB server started on port 3333 (core 0)

• Start gdb client: zephyr-sdk-0.13.1/arm-zephyr-eabi/bin/arm-zephyr-eabi-gdb zephyr/build/zephyr/zephyr.elf

• Connect to gdbserver:

  >>> target remote :3333

• gdb TUI shows below red python value error:

And btw it seems this very python exception will break the Native Debug extension for the Visual Studio Code. See below:

And if I attempt to input some gdb command in the Visual Studio Code DEBUG CONSOLE, it shows below error:

[flit]

Hi @smrtos! I also use both GDB Dashboard for command line debugging, and VSCode for GUI debugging.

The ValueError: max() arg is an empty sequence exception you see is a bug in GDB Dashboard. It's not completely happy with the Cortex-M architecture.

I'm not sure where the "Exception has occurred" error comes from. I don't think that's a result of the GDB Dashboard error, since that's a Python exception (and you can see Dashboard continues to print the rest of the dashboard sections). This error is probably related to the Native Debug extension not being meant for embedded debugging.

So basically, the Native Debug extension should not be used with Cortex-M debugging. Please use the cortex-debug extension instead. It works well with pyocd.

Here's an example cortex-debug launch configuration I use for debugging DAPLink.

{
    "name": "DAPLink lpc55s69_bl",
    "executable": "${workspaceRoot}/projectfiles/make_gcc_arm/lpc55s69_bl/build/lpc55s69_bl.elf",
    "cwd": "${workspaceRoot}",
    "request": "launch",
    "type": "cortex-debug",
    "servertype": "pyocd",
    "serverpath": "${workspaceRoot}/venv/mac39/bin/pyocd",
    "targetId": "lpc55s69",
    "serverArgs": [
        "--uid=L02932983A",
        "--core=0",
    ],
    "svdFile": "/xxx/_cmsis_packs/NXP.LPC55S69_DFP.12.3.0/LPC55S69_cm33_core0.xml",
    "showDevDebugOutput": false,
    "gdbPath": "/opt/gcc-arm-none-eabi-10.3-2021.07/bin/arm-none-eabi-gdb-py",
},

Notes:

• On multicore devices you must include --core=N in the serverArgs or cortex-debug will try to use clashing server ports for the multiple cores.
• Use pyocd's -u/--uid argument in serverArgs to specify the probe's unique ID, if you have multiple boards connected.
• The targetId key is where you put pyocd's -t/--target argument, if needed.
• cortex-debug config attribute documentation is here.

(I plan on adding a full guide to debugging with VSCode+cortex-debug to the pyocd docs soon.)

[smrtos]

Thanks @flit I will try the Cortex Debug extension. I remember I also tried disabling the Native Debug extension but the "Exception has occurred" still showed up. I will double check on that and provide further details.

[smrtos]

@flit Thanks for the recommendation. I just tried it. It seems impossible to configure the port for the gdb client to connect to. The maintainer doesn't consider that to be a proper way I guess. Check here: https://github.com/Marus/cortex-debug/issues/117

[flit]

Hmmm, that's a bit frustrating indeed.