> Complete documentation index: [llms.txt](/llms.txt). Markdown versions of all pages are available by appending `.md` to page URLs.

# UART Passthrough

> The default USB CDC mode: a transparent bridge between the virtual COM port and the device's UART pins.

**Mode `0` · Supernova and Pulsar · Introduced in firmware v4.3.0**

UART Passthrough is the default CDC mode and the one the device ships in. The
virtual COM port is a transparent bridge to the device's UART pins: bytes
written to the port go out on TX, and bytes arriving on RX come back as port input.

Because it is the default, no setup is needed: plug the device in, open the COM
port, and use it like any other USB-to-serial adapter.

## Using it

Set baud rate, data bits, parity and stop bits through the COM port's normal
settings, the same way as for any serial adapter. The device applies them
to the UART.

The USB HID interface stays fully active in this mode, so Mission Control and the
SDKs keep working normally at the same time.

## Returning to this mode

If the device is in another CDC mode, switch back with:

```sh
python device_settings_cli.py set --cdc-mode uart_passthrough
```

See [USB CDC Operating Modes](/guides/usb-interfaces/usb-cdc-operating-modes/) for the full tool reference.