# Transport _USB-serial port_ The box enumerates as a USB-serial device, so it appears as an ordinary serial port. Everything travels over that port as raw bytes. Open the port at the fixed baud, then send [frames](/native/frame.md) and confirm the box with the [handshake](/native/connection.md). ## Serial link _Baud and framing_ Fixed `4,000,000` baud (4 Mbaud), no negotiation. Open the port at that exact baud and start sending bytes; any other baud fails. The box speaks [framed binary](/native/frame.md) from the first byte. There is no legacy startup path: - No ASCII console. - No `115200` startup step. - No baud-switch frame. - Baud is never saved on the box, so a bad setting can't lock you out. ## USB identity _WCH CH343 bridge_ A [WCH](https://www.wch-ic.com) [`CH343`](https://www.wch-ic.com/products/CH343.html) chip does the USB-to-serial conversion. Match on its vendor and product IDs to pick the box out from other serial devices. | Property | Value | | --- | --- | | VID | `0x1A86` | | PID | `0x55D3` | | Baud | `4,000,000` | | Framing | `8N1` | | Linux path | `/dev/ttyACM*` | | Windows path | `COMx` | `8N1` is 8 data bits, no parity, 1 stop bit. > **Note** > > See [Connection](/native/connection.md) for the handshake and [Frame Format](/native/frame.md) for the wire format.