4b1c8d16f7
Documentation tooling:
- Add the `build-doc` skill and `tools/build_doc.py` wrapper for local
Sphinx builds (clean / -W / open).
- Enable Markdown (MyST) in conf.py and auto-collect
examples/{device,host,dual}/*/README.md into a 3-level Examples nav
(Examples > Device/Host/Dual > example), noting each page's source
location and normalizing headings to a single H1.
- Remove the stale `.claude/commands/build-doc.md`; point the AGENTS.md
Documentation section at the skill.
Example docs:
- Add a README.md for every device/host/dual example: what it does, USB
interface table, notable tusb_config.h settings, generic CMake + Make
build steps, and how to try it.
- Fold each *_freertos variant into its base README, noting the FreeRTOS
source path and any RTOS-specific behavior.
Generated docs/examples/ output is git-ignored. Builds clean with
`sphinx-build -W`.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Dynamic Configuration
Demonstrates returning different device and configuration descriptors at enumeration time, selected by the on-board button. The button is sampled when the host requests the device descriptor, so the device enumerates as one of two completely different personalities depending on whether the button is held while plugging in.
What it does
- Reads the on-board button when the host fetches the device descriptor to choose the active configuration.
- Button not pressed — enumerates as CDC + MIDI:
- CDC echoes back received data (and appends a newline after each carriage return); prints a banner when the terminal connects.
- MIDI continuously plays a fixed note sequence, and drains/discards any incoming MIDI.
- Button pressed — enumerates as MSC: presents a small read/write FAT12 RAM disk containing a
README.TXTfile. - Blinks the on-board LED to reflect bus state: 250 ms unmounted, 1000 ms mounted, 2500 ms suspended.
USB Descriptors
Two alternate configurations are served, chosen by the button at enumeration.
Button not pressed (CDC + MIDI):
| Interface | Class driver |
|---|---|
| 0–1 | CDC (virtual serial) |
| 2–3 | MIDI |
Button pressed (MSC):
| Interface | Class driver |
|---|---|
| 0 | MSC (mass storage) |
Configuration
Notable tusb_config.h settings (both personalities share one config):
#define CFG_TUD_CDC 1
#define CFG_TUD_MSC 1
#define CFG_TUD_MIDI 1
#define CFG_TUD_CDC_RX_BUFSIZE (TUD_OPT_HIGH_SPEED ? 512 : 64)
#define CFG_TUD_CDC_TX_BUFSIZE (TUD_OPT_HIGH_SPEED ? 512 : 64)
#define CFG_TUD_MIDI_RX_BUFSIZE (TUD_OPT_HIGH_SPEED ? 512 : 64)
#define CFG_TUD_MIDI_TX_BUFSIZE (TUD_OPT_HIGH_SPEED ? 512 : 64)
#define CFG_TUD_MSC_EP_BUFSIZE 512
Building
CMake:
mkdir build && cd build
cmake -DBOARD=raspberry_pi_pico ..
cmake --build .
Make:
make BOARD=raspberry_pi_pico all
Try it
Plug the board in normally: a serial port and a MIDI device appear on the host. Now hold the on-board button while plugging in (or while resetting): the device instead enumerates as a removable drive with a README.TXT file. The two personalities use different product IDs so the host treats them as distinct devices.