1. Documentation
  2. Engineering
  3. USB hardware endpoint

Design

USB hardware endpoint

This is the agreed USB product design. The prototype uses two Radxa ZERO 3E boards, one in each Yoke box. USB 2 is the first deliverable.

Physical connection

USB device — USB — Yoke box ⇄ Ethernet switch ⇄ Yoke box — USB — computer
                  device side                  computer side

The device-side box connects to the USB peripheral and acts as its USB host. The computer-side box connects by USB to the user's computer and presents the remote device to it. Requests and responses travel in both directions through the boxes and the Ethernet network.

The computer is outside the two-box system. It does not run the Yoke endpoint software. The product does not require that computer to run Linux. Linux inside a ZERO 3E box is a firmware implementation choice. Supported USB device types and computer compatibility still need testing; this design is not a claim that every USB peripheral already works.

Pairing and management

Each box runs independently. The computer-side box stores its chosen device-side box. That pairing survives a restart or a lost connection and changes only when a pair or unpair command changes it. An unavailable box leaves the saved pairing in place while the system waits for it to return.

Thermite can manage the boxes, but is optional. The command-line tool or another manager can use the documented protocol. Management and USB network transport must use open, published protocols that others can implement. There must be no undocumented control commands or backdoor management paths. Closing a manager does not clear a pairing. Configuration and status must remain documented and available without a proprietary management service.

Prototype scope

  • Two Radxa ZERO 3E boards, with one physical USB connection at each end.
  • USB 2 first. Earlier USB 3 and 10GbE research does not set requirements for this prototype.
  • Ethernet between the boxes. The bare board does not supply a completed PoE product; power wiring and any PoE adapter need separate validation.
  • The enclosure is being redesigned after two failed prints: rectangular shell, slot joint, recessed M3 screws and heat-set inserts.

Firmware status

The pairing software, stored state, monitoring and Linux USB/IP adapter exist. The current USB/IP adapter can export devices and import them into a Linux kernel. That adapter alone does not complete this hardware product.

The computer-side box still needs the USB device/gadget bridge that presents the remote peripheral through its physical USB port. That work, USB device compatibility, recovery and end-to-end hardware testing remain unfinished. Do not replace the computer-side box with a Linux application host in product documentation or drawings to match the current adapter.

The first hardware test must cover the complete path above, including the second box and its USB cable to a separate computer. A successful Linux USB/IP import is a backend test, not completion of that test.

The backend reference describes the existing adapter. The older 10G/USB3 study and hardware survey remain historical research; their NanoPi/VirtualHere recommendations do not replace the selected ZERO 3E design.