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Debugging your code

You can debug your code while it is running in the simulation using the VS Code debugger. To set up the debugger, follow these steps:

Configure Wokwi​

Add the following line to the [wokwi] section of your wokwi.toml configuration file:

gdbServerPort=3333

Configure VS Code​

Create a launch configuration file for VS Code at .vscode/launch.json. Here's a template you can use:

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Wokwi GDB",
      "type": "cppdbg",
      "request": "launch",
      "program": "${workspaceFolder}/build/your-firmware.elf",
      "cwd": "${workspaceFolder}",
      "MIMode": "gdb",
      "miDebuggerPath": "/usr/local/bin/xtensa-esp32-elf-gdb",
      "miDebuggerServerAddress": "localhost:3333"
    }
  ]
}

The type describes the VS Code extension used here. In this case cppdbg. Therefore the following extension must be installed: https://marketplace.visualstudio.com/items?itemName=ms-vscode.cpptools

Replace the program path with the path to your firmware's ELF file, and the miDebuggerPath with the path to a GDB executable that supports your project's architecture (e.g. for AVR projects, use avr-gdb).

ESP-IDF projects​

For ESP-IDF projects, you can set the miDebuggerPath to "${command:espIdf.getToolchainGdb}", and the debugger will automatically use the correct GDB executable (this requires the ESP-IDF extension to be installed). For a complete example, check out the ESP32 Hello WiFi debug configuration.

PlatformIO projects​

PlatformIO provides a precompiled version of GDB that you can use. For example, the debug an ESP32 project, you can set the miDebuggerPath to "${userHome}/.platformio/packages/toolchain-xtensa-esp32/bin/xtensa-esp32-elf-gdb.exe" on Windows, or "${userHome}/.platformio/packages/toolchain-xtensa-esp32/bin/xtensa-esp32-elf-gdb" on macOS and Linux.

Arduino (AVR) projects​

For Arduino projects, you need to use a recent version of GDB. The version that comes with the Arduino IDE (7.8) is too old, and will fail with an error: "ERROR: Unable to start debugging. Failed to find thread 1 for break event".

You can download a recent version of avr-gdb from here (Windows/Linux) or here (macOS, using Homebrew).

Start the debugger​

Before starting the simulator, build your software for the target to simulate.

info

Building the "debug" configuration can simplify the analysis of the program execution while debugging.

Start the Wokwi simulator by pressing F1 and then selecting "Wokwi: Start Simulator and Wait for Debugger". The simulator will load, but the program will be paused, waiting for the debugger to connect. Then press F5 to start the debugger.

warning

You need to start Wokwi before starting the debugger. If you start the debugger first, it will fail to connect to the simulator.

Troubleshooting​

If you get an error message saying "Remote 'g' packet reply is too long", you are probably using a GDB version that is incompatible with the microcontroller architecture (e.g. using avr-gdb with an ESP32 project). Make sure you are using the correct GDB version for your project's microcontroller.