.github/copilot-instructions.md - third_party/github/hathach/tinyusb - Git at Google

 # TinyUSB
 TinyUSB is an open-source cross-platform USB Host/Device stack for embedded systems, designed to be memory-safe with no dynamic allocation and thread-safe with all interrupt events deferred to non-ISR task functions.

 Always reference these instructions first and fallback to search or bash commands only when you encounter unexpected information that does not match the info here.

 ## Working Effectively

 ### Bootstrap and Build Setup
 - Install ARM GCC toolchain: `sudo apt-get update && sudo apt-get install -y gcc-arm-none-eabi`
 - Fetch core dependencies: `python3 tools/get_deps.py` -- takes <1 second. NEVER CANCEL.
 - For specific board families: `python3 tools/get_deps.py FAMILY_NAME` (e.g., rp2040, stm32f4)
 - Dependencies are cached in `lib/` and `hw/mcu/` directories

 ### Build Examples
 Choose ONE of these approaches:

 **Option 1: Individual Example with CMake (RECOMMENDED)**
 ```bash
 cd examples/device/cdc_msc
 mkdir -p build && cd build
 cmake -DBOARD=raspberry_pi_pico -DCMAKE_BUILD_TYPE=MinSizeRel ..
 cmake --build . -j4
 ```
 -- takes 1-2 seconds. NEVER CANCEL. Set timeout to 5+ minutes.

 **CMake with Ninja (Alternative)**
 ```bash
 cd examples/device/cdc_msc
 mkdir build && cd build
 cmake -G Ninja -DBOARD=raspberry_pi_pico ..
 ninja
 ```

 **Option 2: Individual Example with Make**
 ```bash
 cd examples/device/cdc_msc
 make BOARD=raspberry_pi_pico all
 ```
 -- takes 2-3 seconds. NEVER CANCEL. Set timeout to 5+ minutes.

 **Option 3: All Examples for a Board**
 ```bash
 python3 tools/build.py -b BOARD_NAME
 ```
 -- takes 15-20 seconds, may have some objcopy failures that are non-critical. NEVER CANCEL. Set timeout to 30+ minutes.

 ### Build Options
 - **Debug build**:
   - CMake: `-DCMAKE_BUILD_TYPE=Debug`
   - Make: `DEBUG=1`
 - **With logging**:
   - CMake: `-DLOG=2`
   - Make: `LOG=2`
 - **With RTT logger**:
   - CMake: `-DLOG=2 -DLOGGER=rtt`
   - Make: `LOG=2 LOGGER=rtt`
 - **RootHub port selection**:
   - CMake: `-DRHPORT_DEVICE=1`
   - Make: `RHPORT_DEVICE=1`
 - **Port speed**:
   - CMake: `-DRHPORT_DEVICE_SPEED=OPT_MODE_FULL_SPEED`
   - Make: `RHPORT_DEVICE_SPEED=OPT_MODE_FULL_SPEED`

 ### Flashing and Deploymen
 - **Flash with JLink**:1
   - CMake: `ninja cdc_msc-jlink`
   - Make: `make BOARD=raspberry_pi_pico flash-jlink`
 - **Flash with OpenOCD**:
   - CMake: `ninja cdc_msc-openocd`
   - Make: `make BOARD=raspberry_pi_pico flash-openocd`
 - **Generate UF2**:
   - CMake: `ninja cdc_msc-uf2`
   - Make: `make BOARD=raspberry_pi_pico all uf2`
 - **List all targets** (CMake/Ninja): `ninja -t targets`

 ### Unit Testing
 - Install Ceedling: `sudo gem install ceedling`
 - Run all unit tests: `cd test/unit-test && ceedling` or `cd test/unit-test && ceedling test:all` -- takes 4 seconds. NEVER CANCEL. Set timeout to 10+ minutes.
 - Run specific test: `cd test/unit-test && ceedling test:test_fifo`
 - Tests use Unity framework with CMock for mocking

 ### Documentation
 - Install requirements: `pip install -r docs/requirements.txt`
 - Build docs: `cd docs && sphinx-build -b html . _build` -- takes 2-3 seconds. NEVER CANCEL. Set timeout to 10+ minutes.

 ### Code Quality and Validation
 - Format code: `clang-format -i path/to/file.c` (uses `.clang-format` config)
 - Check spelling: `pip install codespell && codespell` (uses `.codespellrc` config)
 - Pre-commit hooks validate unit tests and code quality automatically

 ## Validation

 ### ALWAYS Run These After Making Changes
 1. **Pre-commit validation** (RECOMMENDED): `pre-commit run --all-files`
    - Install pre-commit: `pip install pre-commit && pre-commit install`
    - Runs all quality checks, unit tests, spell checking, and formatting
    - Takes 10-15 seconds. NEVER CANCEL. Set timeout to 15+ minutes.
 2. **Build validation**: Build at least one example that exercises your changes
    ```bash
    cd examples/device/cdc_msc
    make BOARD=raspberry_pi_pico all
    ```

 ### Manual Testing Scenarios
 - **Device examples**: Cannot be fully tested without real hardware, but must build successfully
 - **Unit tests**: Exercise core stack functionality - ALL tests must pass
 - **Build system**: Must be able to build examples for multiple board families

 ### Board Selection for Testing
 - **STM32F4**: `stm32f407disco` - no external SDK required, good for testing
 - **RP2040**: `raspberry_pi_pico` - requires Pico SDK, commonly used
 - **Other families**: Check `hw/bsp/FAMILY/boards/` for available boards

 ## Common Tasks and Time Expectations

 ### Repository Structure Quick Reference
 ```
 ├── src/                  # Core TinyUSB stack
 │   ├── class/            # USB device classes (CDC, HID, MSC, Audio, etc.)
 │   ├── portable/         # MCU-specific drivers (organized by vendor)
 │   ├── device/           # USB device stack core
 │   ├── host/             # USB host stack core
 │   └── common/           # Shared utilities (FIFO, etc.)
 ├── examples/             # Example applications
 │   ├── device/           # Device examples (cdc_msc, hid_generic, etc.)
 │   ├── host/             # Host examples
 │   └── dual/             # Dual-role examples
 ├── hw/bsp/               # Board Support Packages
 │   └── FAMILY/boards/    # Board-specific configurations
 ├── test/unit-test/       # Unit tests using Ceedling
 ├── tools/                # Build and utility scripts
 └── docs/                 # Sphinx documentation
 ```

 ### Build Time Reference
 - **Dependency fetch**: <1 second
 - **Single example build**: 1-3 seconds
 - **Unit tests**: ~4 seconds
 - **Documentation build**: ~2.5 seconds
 - **Full board examples**: 15-20 seconds
 - **Toolchain installation**: 2-5 minutes (one-time)

 ### Key Files to Know
 - `tools/get_deps.py`: Manages dependencies for MCU families
 - `tools/build.py`: Builds multiple examples, supports make/cmake
 - `src/tusb.h`: Main TinyUSB header file
 - `src/tusb_config.h`: Configuration template
 - `examples/device/cdc_msc/`: Most commonly used example for testing
 - `test/unit-test/project.yml`: Ceedling test configuration

 ### Debugging Build Issues
 - **Missing compiler**: Install `gcc-arm-none-eabi` package
 - **Missing dependencies**: Run `python3 tools/get_deps.py FAMILY`
 - **Board not found**: Check `hw/bsp/FAMILY/boards/` for valid board names
 - **objcopy errors**: Often non-critical in full builds, try individual example builds

 ### Working with USB Device Classes
 - **CDC (Serial)**: `src/class/cdc/` - Virtual serial port
 - **HID**: `src/class/hid/` - Human Interface Device (keyboard, mouse, etc.)
 - **MSC**: `src/class/msc/` - Mass Storage Class (USB drive)
 - **Audio**: `src/class/audio/` - USB Audio Class
 - Each class has device (`*_device.c`) and host (`*_host.c`) implementations

 ### MCU Family Support
 - **STM32**: Largest support (F0, F1, F2, F3, F4, F7, G0, G4, H7, L4, U5, etc.)
 - **Raspberry Pi**: RP2040, RP2350 with PIO-USB host support
 - **NXP**: iMXRT, Kinetis, LPC families
 - **Microchip**: SAM D/E/G/L families
 - Check `hw/bsp/` for complete list and `docs/reference/boards.rst` for details

 ## Code Style Guidelines

 ### General Coding Standards
 - Use C99 standard
 - Memory-safe: no dynamic allocation
 - Thread-safe: defer all interrupt events to non-ISR task functions
 - 2-space indentation, no tabs
 - Use snake_case for variables/functions
 - Use UPPER_CASE for macros and constants
 - Follow existing variable naming patterns in files you're modifying
 - Include proper header comments with MIT license
 - Add descriptive comments for non-obvious functions

 ### Best Practices
 - When including headers, group in order: C stdlib, tusb common, drivers, classes
 - Always check return values from functions that can fail
 - Use TU_ASSERT() for error checking with return statements
 - Follow the existing code patterns in the files you're modifying

 Remember: TinyUSB is designed for embedded systems - builds are fast, tests are focused, and the codebase is optimized for resource-constrained environments.
	# TinyUSB
	TinyUSB is an open-source cross-platform USB Host/Device stack for embedded systems, designed to be memory-safe with no dynamic allocation and thread-safe with all interrupt events deferred to non-ISR task functions.

	Always reference these instructions first and fallback to search or bash commands only when you encounter unexpected information that does not match the info here.

	## Working Effectively

	### Bootstrap and Build Setup
	- Install ARM GCC toolchain: `sudo apt-get update && sudo apt-get install -y gcc-arm-none-eabi`
	- Fetch core dependencies: `python3 tools/get_deps.py` -- takes <1 second. NEVER CANCEL.
	- For specific board families: `python3 tools/get_deps.py FAMILY_NAME` (e.g., rp2040, stm32f4)
	- Dependencies are cached in `lib/` and `hw/mcu/` directories

	### Build Examples
	Choose ONE of these approaches:

	Option 1: Individual Example with CMake (RECOMMENDED)
	```bash
	cd examples/device/cdc_msc
	mkdir -p build && cd build
	cmake -DBOARD=raspberry_pi_pico -DCMAKE_BUILD_TYPE=MinSizeRel ..
	cmake --build . -j4
	```
	-- takes 1-2 seconds. NEVER CANCEL. Set timeout to 5+ minutes.

	CMake with Ninja (Alternative)
	```bash
	cd examples/device/cdc_msc
	mkdir build && cd build
	cmake -G Ninja -DBOARD=raspberry_pi_pico ..
	ninja
	```

	Option 2: Individual Example with Make
	```bash
	cd examples/device/cdc_msc
	make BOARD=raspberry_pi_pico all
	```
	-- takes 2-3 seconds. NEVER CANCEL. Set timeout to 5+ minutes.

	Option 3: All Examples for a Board
	```bash
	python3 tools/build.py -b BOARD_NAME
	```
	-- takes 15-20 seconds, may have some objcopy failures that are non-critical. NEVER CANCEL. Set timeout to 30+ minutes.

	### Build Options
	- Debug build:
	- CMake: `-DCMAKE_BUILD_TYPE=Debug`
	- Make: `DEBUG=1`
	- With logging:
	- CMake: `-DLOG=2`
	- Make: `LOG=2`
	- With RTT logger:
	- CMake: `-DLOG=2 -DLOGGER=rtt`
	- Make: `LOG=2 LOGGER=rtt`
	- RootHub port selection:
	- CMake: `-DRHPORT_DEVICE=1`
	- Make: `RHPORT_DEVICE=1`
	- Port speed:
	- CMake: `-DRHPORT_DEVICE_SPEED=OPT_MODE_FULL_SPEED`
	- Make: `RHPORT_DEVICE_SPEED=OPT_MODE_FULL_SPEED`

	### Flashing and Deploymen
	- Flash with JLink:1
	- CMake: `ninja cdc_msc-jlink`
	- Make: `make BOARD=raspberry_pi_pico flash-jlink`
	- Flash with OpenOCD:
	- CMake: `ninja cdc_msc-openocd`
	- Make: `make BOARD=raspberry_pi_pico flash-openocd`
	- Generate UF2:
	- CMake: `ninja cdc_msc-uf2`
	- Make: `make BOARD=raspberry_pi_pico all uf2`
	- List all targets (CMake/Ninja): `ninja -t targets`

	### Unit Testing
	- Install Ceedling: `sudo gem install ceedling`
	- Run all unit tests: `cd test/unit-test && ceedling` or `cd test/unit-test && ceedling test:all` -- takes 4 seconds. NEVER CANCEL. Set timeout to 10+ minutes.
	- Run specific test: `cd test/unit-test && ceedling test:test_fifo`
	- Tests use Unity framework with CMock for mocking

	### Documentation
	- Install requirements: `pip install -r docs/requirements.txt`
	- Build docs: `cd docs && sphinx-build -b html . _build` -- takes 2-3 seconds. NEVER CANCEL. Set timeout to 10+ minutes.

	### Code Quality and Validation
	- Format code: `clang-format -i path/to/file.c` (uses `.clang-format` config)
	- Check spelling: `pip install codespell && codespell` (uses `.codespellrc` config)
	- Pre-commit hooks validate unit tests and code quality automatically

	## Validation

	### ALWAYS Run These After Making Changes
	1. Pre-commit validation (RECOMMENDED): `pre-commit run --all-files`
	- Install pre-commit: `pip install pre-commit && pre-commit install`
	- Runs all quality checks, unit tests, spell checking, and formatting
	- Takes 10-15 seconds. NEVER CANCEL. Set timeout to 15+ minutes.
	2. Build validation: Build at least one example that exercises your changes
	```bash
	cd examples/device/cdc_msc
	make BOARD=raspberry_pi_pico all
	```

	### Manual Testing Scenarios
	- Device examples: Cannot be fully tested without real hardware, but must build successfully
	- Unit tests: Exercise core stack functionality - ALL tests must pass
	- Build system: Must be able to build examples for multiple board families

	### Board Selection for Testing
	- STM32F4: `stm32f407disco` - no external SDK required, good for testing
	- RP2040: `raspberry_pi_pico` - requires Pico SDK, commonly used
	- Other families: Check `hw/bsp/FAMILY/boards/` for available boards

	## Common Tasks and Time Expectations

	### Repository Structure Quick Reference
	```
	├── src/ # Core TinyUSB stack
	│ ├── class/ # USB device classes (CDC, HID, MSC, Audio, etc.)
	│ ├── portable/ # MCU-specific drivers (organized by vendor)
	│ ├── device/ # USB device stack core
	│ ├── host/ # USB host stack core
	│ └── common/ # Shared utilities (FIFO, etc.)
	├── examples/ # Example applications
	│ ├── device/ # Device examples (cdc_msc, hid_generic, etc.)
	│ ├── host/ # Host examples
	│ └── dual/ # Dual-role examples
	├── hw/bsp/ # Board Support Packages
	│ └── FAMILY/boards/ # Board-specific configurations
	├── test/unit-test/ # Unit tests using Ceedling
	├── tools/ # Build and utility scripts
	└── docs/ # Sphinx documentation
	```

	### Build Time Reference
	- Dependency fetch: <1 second
	- Single example build: 1-3 seconds
	- Unit tests: ~4 seconds
	- Documentation build: ~2.5 seconds
	- Full board examples: 15-20 seconds
	- Toolchain installation: 2-5 minutes (one-time)

	### Key Files to Know
	- `tools/get_deps.py`: Manages dependencies for MCU families
	- `tools/build.py`: Builds multiple examples, supports make/cmake
	- `src/tusb.h`: Main TinyUSB header file
	- `src/tusb_config.h`: Configuration template
	- `examples/device/cdc_msc/`: Most commonly used example for testing
	- `test/unit-test/project.yml`: Ceedling test configuration

	### Debugging Build Issues
	- Missing compiler: Install `gcc-arm-none-eabi` package
	- Missing dependencies: Run `python3 tools/get_deps.py FAMILY`
	- Board not found: Check `hw/bsp/FAMILY/boards/` for valid board names
	- objcopy errors: Often non-critical in full builds, try individual example builds

	### Working with USB Device Classes
	- CDC (Serial): `src/class/cdc/` - Virtual serial port
	- HID: `src/class/hid/` - Human Interface Device (keyboard, mouse, etc.)
	- MSC: `src/class/msc/` - Mass Storage Class (USB drive)
	- Audio: `src/class/audio/` - USB Audio Class
	- Each class has device (`_device.c`) and host (`_host.c`) implementations

	### MCU Family Support
	- STM32: Largest support (F0, F1, F2, F3, F4, F7, G0, G4, H7, L4, U5, etc.)
	- Raspberry Pi: RP2040, RP2350 with PIO-USB host support
	- NXP: iMXRT, Kinetis, LPC families
	- Microchip: SAM D/E/G/L families
	- Check `hw/bsp/` for complete list and `docs/reference/boards.rst` for details

	## Code Style Guidelines

	### General Coding Standards
	- Use C99 standard
	- Memory-safe: no dynamic allocation
	- Thread-safe: defer all interrupt events to non-ISR task functions
	- 2-space indentation, no tabs
	- Use snake_case for variables/functions
	- Use UPPER_CASE for macros and constants
	- Follow existing variable naming patterns in files you're modifying
	- Include proper header comments with MIT license
	- Add descriptive comments for non-obvious functions

	### Best Practices
	- When including headers, group in order: C stdlib, tusb common, drivers, classes
	- Always check return values from functions that can fail
	- Use TU_ASSERT() for error checking with return statements
	- Follow the existing code patterns in the files you're modifying

	Remember: TinyUSB is designed for embedded systems - builds are fast, tests are focused, and the codebase is optimized for resource-constrained environments.