This chapter explores the basic characteristics of the Universal Serial Bus (USB) and introduces WinDriver USB's features and architecture.
|The references to the WinDriver USB toolkit in this chapter relate to the standard WinDriver USB toolkit for development of USB host drivers.|
USB (Universal Serial Bus) is an industry standard extension to the PC architecture for attaching peripherals to the computer. It was originally developed in 1995 by leading PC and telecommunication industry companies, such as Intel, Compaq, Microsoft and NEC. USB was developed to meet several needs, among them the needs for an inexpensive and widespread connectivity solution for peripherals in general and for computer telephony integration in particular, an easy-to-use and flexible method of reconfiguring the PC, and a solution for adding a large number of external peripherals. The USB standard meets these needs.
The USB specification allows for the connection of a maximum of 127 peripheral devices (including hubs) to the system, either on the same port or on different ports.
USB also supports Plug-and-Play installation and hot swapping. The USB 1.1 standard supports both isochronous and asynchronous data transfers and has dual speed data transfer: 1.5 Mb/s (megabits per second) for low-speed USB devices and 12 Mb/s for full-speed USB devices (much faster than the original serial port). Cables connecting the device to the PC can be up to five meters (16.4 feet) long. USB includes built-in power distribution for low power devices and can provide limited power (up to 500 mA of current) to devices attached on the bus.
The USB 2.0 standard supports a signalling rate of 480 Mb/s, known
as 'high-speed', which is 40 times faster than the USB 1.1 full-speed
USB 2.0 is fully forward- and backward-compatible with USB 1.1 and uses existing cables and connectors.
USB 2.0 supports connections with PC peripherals that provide expanded functionality and require wider bandwidth. In addition, it can handle a larger number of peripherals simultaneously.
USB 2.0 enhances the user's experience of many applications, including interactive gaming, broadband Internet access, desktop and Web publishing, Internet services and conferencing.
Because of its benefits (described also in section 3.2 below), USB is currently enjoying broad market acceptance.