Section
Overview
Protocol
Commands
Reference
AI Access
Medius Native API
The binary control protocolMedius is replacement firmware for MAKCU-class USB input-passthrough boxes plus an open binary control protocol. The box sits inline between a USB device and a PC: the real device (mouse, keyboard, or combo) passes through unchanged while your program injects input of its own (cursor and buttons for a mouse, keys and media for a keyboard) over a separate USB-serial link. Drive it from any language; the Rust library is the official client.
| Property | Value |
|---|---|
| Firmware version | 3.0.0 |
| Protocol version | 3 |
| Transport | 4 Mbaud, framed-only (CH343) |
| USB ID | VID 0x1A86 / PID 0x55D3 |
| Delivery | Fire-and-forget; QUERY → RESP is the only round-trip |
Before you talk to the box:
| Topic | What to know |
|---|---|
| Protocol version | These pages describe version 3. Confirm it during the handshake from the proto_ver field of the VERSION reply; a different value means firmware these pages don't cover. |
| Wire format | The box speaks framed binary from the first byte. No startup baud, no text mode. |
| Finding the port | Scan for the CH343's VID/PID pair to locate the box's serial port. |
| Correlation | Fire-and-forget has no ack or echo. A QUERY is correlated to its RESP by SEQ. |