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This project provides open-source API for low-cost USB HID relays (search on eBay for "5V USB Relay Programmable Computer Control For Smart Home").

The big advantage of HID-based interface is that no kernel drivers and no simulated COM-ports are needed. It is easy to detect and address the connected devices. Ebay vendors currently offer only an API library for Windows, and only in binary form.

We are not associated with the manufacturer(s) of these devices or author(s) of the original software offered by ebay sellers.

The project home page is on the V-USB wiki - because the firmware of the device is based on V-USB. V-USB enables amazingly simple and low-cost USB hardware solutions.
This repository contains only the host side software.

Binary downloads, documentation, bugs, TO-DOs and more

All this is in the Github project : releases, wiki pages and Issues.

Current state

  • A simple command-line utility for Linux (x86 or x64), Apple OS X and Windows (XP and newer, 32 and 64-bit).

  • Shared library for Linux (x86 or x64), Apple OS X and Windows.

  • Python (CPython) - supported thru the shared library

The Windows version of the shared lib, USB_RELAY_DEVICE.DLL, is backward compatible with the binary from the device vendor. Windows GUI demo app is similar to the device vendor's but written in C++/CLI.

Required to build:

  • Windows version: builds with VC++ and WDK 7.1, or VC++ 2013 "community edition" with its matching SDK (Win8.1).
  • Linux version builds with gcc and libusb v. 0.1. Tested on RH, Ubuntu, Mint.
  • OS-X 10.9+ version builds with Xcode and plain IOKit libraries.


Currently we reuse some code from other V-USB projects, which is dual-licensed: GPL + commercial. Until we remove this code, we cannot set any other license.

We could not locate any copyright information in the software package offered by the eBay sellers. No source code was reused from that package, besides of the C API header (the .h file).