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Speed-switched desc_device_ss (bcdUSB 0x0320, bMaxPacketSize0 = 9), SuperSpeed config arrays from the TUD_*_SS_DESCRIPTOR templates, BOS, and EP0 / bulk buffer sizing for SuperSpeed across the device examples.
CDC + MSC
A composite USB device that exposes two interfaces at once:
- CDC — a virtual serial port (
/dev/ttyACMx, or a COM port on Windows) that echoes back everything it receives. - MSC — a small mass-storage disk that mounts as a removable drive.
This is the canonical TinyUSB example for a multi-interface (composite) device.
What it does
- CDC: reads incoming data and echoes it straight back. Pressing the on-board button sends a serial-state (UART) notification to the host.
- MSC: presents an 8 KB FAT12 RAM disk (16 × 512-byte blocks — the smallest size Windows will mount) labelled
TinyUSB MSC, containing a singleREADME.TXT. The disk lives in RAM, so changes are not persistent. - LED shows bus state: 250 ms blink = not mounted, 1000 ms = mounted, 2500 ms = suspended.
USB Descriptors
| Interface | Class driver |
|---|---|
| 0–1 | CDC (virtual serial) |
| 2 | MSC (mass storage) |
Configuration
Notable tusb_config.h settings:
#define CFG_TUD_CDC 1
#define CFG_TUD_MSC 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_MSC_EP_BUFSIZE 512
Building
CMake:
mkdir build && cd build
cmake -DBOARD=raspberry_pi_pico ..
cmake --build .
Make:
make BOARD=raspberry_pi_pico all
FreeRTOS variant
A FreeRTOS build is in examples/device/cdc_msc_freertos — identical CDC + MSC behavior, with the device, CDC, and LED-blink work split across FreeRTOS tasks.
Try it
- Serial: open the CDC port (
screen /dev/ttyACM0, PuTTY, …) and type — characters are echoed back. - Storage: a small
TinyUSB MSCdrive appears; openREADME.TXTto confirm it mounted.