NOTE (Debug)

Debugging with gdb, pyOCD and VS Code

Debug System Structure

Visual Studio Code (as a debugger UI)

C/C++ for Visual Studio Code

arm-none-eabi-gdb

pyOCD

USB

The debug target (micro:bit device)

Module Outlines

• Visual Studio Code (VS Code)

  • https://code.visualstudio.com

• C/C++ for Visual Studio Code

  • A VS Code extension for debugging with C/C++ source code
  • https://marketplace.visualstudio.com/items?itemName=ms-vscode.cpptools

• arm-none-eabi-gdb

  • A generic debugger with MI (Machine Interface)
  • Included in arm-none-eabi-gcc toolchain

• pyOCD

  • A debug server to debug an Arm Cortex-M microcontroller via CMSIS-DAP
  • https://github.com/mbedmicro/pyOCD

About .vscode/launch.json

• .vscode/launch.json is a configuration file used by VS Code for debugging.

Instructions to Start Debugging

1. Build the executable suitable for debugging using the following commands.

   • yotta build --debug-build (or yt build -d)

   Note that the following file is required to suppress the compile error of nrf51-sdk for a debug build.

   • source/suppress-errors.nrf51-sdk.cmake

2. Flash the combined.hex file (microbit-dal-ext-kit-example-combined.hex) to the device.

3. Launch VS Code and open the project root folder (microbit-dal-ext-kit-example).

4. On VS Code, select Debug -> Start Debugging (F5) to start a debug session using .vscode/launch.json.

5. The debugger automatically stops at funciton main().

For the general topics regarding debugger, see also References (Debugging Tools).

Hints for Customizing launch.json

• Configuring launch.json for C/C++ debugging

  • https://github.com/Microsoft/vscode-cpptools/blob/master/launch.md

• The list of options available in launch.json

  • https://github.com/Microsoft/MIEngine/blob/master/src/MICore/LaunchOptions.xsd

Troubleshooting

• If the debugger does not stop at function main() after starting the debug session, kill the following processes and try again.

  • arm-none-eabi-gdb
  • pyocd

• If you are in trouble with VS Code and launch.json, verify gdb and pyOCD behavior without VS Code.
  The following note would be a good guide for you.

  • Debugging with pyOCD!
    • https://os.mbed.com/users/maclobdell/notebook/debugging-with-pyocd