This documentation will give an overview of how the OpenUSB external API works and relates to USB. libusb 1.0 API has been discussed and agreed by users and developers in libusb developers mailing list . The API defined in this version is stablized and will not probably be changed in the near future.
OpenUSB or libopenusb is one of the implementation of libusb 1.0 API. It fully comply with libusb 1.0 API. In documents hereafter, OpenUSB and libusb may be used mutually, except when it's neccesary to explicitly clarify.
This documentation assumes that you have a good understanding of USB and how it works.
OpenUSB supports USB v1.1 and v2.0.
The USB 1.1 and 2.0 specification can be found at http://www.usb.org/.