WebUSB Serial

A WebUSB device that acts as a web serial bridge, reachable directly from a WebUSB-capable browser (e.g. Chrome). It also exposes a standard CDC virtual serial port, and bridges traffic between the two.

What it does

Exposes a Vendor (WebUSB) interface plus a CDC virtual serial port.
Echoes any data received on either the WebUSB or the CDC interface back to both of them.
Serves a WebUSB landing-page URL (example.tinyusb.org/webusb-serial/index.html) via a BOS descriptor, so a supporting browser can offer to open the page.
Provides a Microsoft OS 2.0 descriptor so Windows auto-binds the WinUSB driver to the WebUSB interface.
Treats a vendor control request as a connect/disconnect signal from the browser; lights the on-board LED solid while the web serial is connected.
Blinks the on-board LED to reflect bus state: 250 ms unmounted, 1000 ms mounted, 2500 ms suspended.

USB Descriptors

Interface	Class driver
0–1	CDC (virtual serial)
2	Vendor (WebUSB)

Configuration

Notable tusb_config.h settings:

#define CFG_TUD_CDC               1
#define CFG_TUD_VENDOR            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_VENDOR_RX_BUFSIZE (TUD_OPT_HIGH_SPEED ? 512 : 64)
#define CFG_TUD_VENDOR_TX_BUFSIZE (TUD_OPT_HIGH_SPEED ? 512 : 64)

Building

CMake:

bash

mkdir build && cd build
cmake -DBOARD=raspberry_pi_pico ..
cmake --build .

Make:

bash

make BOARD=raspberry_pi_pico all

Try it

After flashing, open the landing page (https://example.tinyusb.org/webusb-serial/index.html) in a WebUSB-capable browser such as Chrome, click Connect, and select the device — the on-board LED lights solid once connected. Characters typed in the web page are echoed back, and are also mirrored to the CDC serial port (e.g. /dev/ttyACM0) and vice versa.

On Linux/macOS you may need to install the udev rules from examples/device/99-tinyusb.rules for the browser to access the device.