Browse Prior Art Database

A Means To Reliably Distinguish And Identify Multiple Identical USB Devices

IP.com Disclosure Number: IPCOM000013498D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Abstract

In the point-of-sale (POS) environment, multiple identical devices (displays) are used quite commonly, hence the need to distinguish between them. In the SIO environment, this problem is solved with a special port hardwares (primary and secondary ports). Once the displays are plugged into the port, the display firmware will be able to detect the hardware difference between the ports and assume the proper port role i.e. display plugged into a primary port will be primary display. This method allows displays to be manufactured identically regarless of their role (primary and secondary).

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 56% of the total text.

Page 1 of 1

A Means To Reliably Distinguish And Identify Multiple Identical USB Devices

In the point-of-sale (POS) environment, multiple identical devices (displays) are used quite commonly, hence the need to distinguish between them. In the SIO environment, this problem is solved with a special port hardwares (primary and secondary ports). Once the displays are plugged into the port, the display firmware will be able to detect the hardware difference between the ports and assume the proper port role i.e. display plugged into a primary port will be primary display. This method allows displays to be manufactured identically regarless of their role (primary and secondary).

In the USB arena, special hardware modifications are not allowed if industry standards are to be followed. Consequently, a new software scheme is designed to assign the display role based on the order they are discovered in the USB network.

The USB devices will be discovered depth-first and the device roles are assigned based on the order that the identical devices were found. Primary devices will have their role assigned then secondary devices, and tercery devices, and so on. This USB network tree traversal order is independent from the USB device discovery mechanism of an operating system. As a result, this method is independent not only from the underlying software platforms but also the underlying hardware platforms (different host PCs, etc.) The crux of this role assignment scheme relies on the relative...