Transcript Slide 1
USB (Universal Serial Bus) What is USB? • Universal Serial Bus (USB) is a serial bus standard to interface devices to a host computer • It was designed to allow many peripherals to be connected using a single standardized interface socket and to improve the Plug and play capabilities by allowing hot swapping or hot plugging Why? • Ease of adding peripherals to PC • Low cost, supporting transfer rates of up to 480 Mbps • Support for many configurations of OS and PC’s • Standard interface for peripherals in general • Plug and Play technology • No need for external power Overview • Multiple peripheral devices connected in a tiered-star topology up to 5 levels • Up to 127 devices, including the hub device • USB 1.0, 1.1 and 2.0 use a "speak-when-spokento“ protocol • Offers limited power How was it created? • USB was developed by a consortium of large companies, such as: -Microsoft; -IBM; -Apple; -Hewlett-Packard; -NEC; -Intel; -Compaq; -Digital; -Northern Telecom; -Philips; -... Curiosity about the consortium • Obviously it was very difficult for these companies enter into agreement • Intel - UHCI - Universal Host Controller Interface (transfer part of the protocol processing for the software (driver), simplifying the electronic controller) • Compaq, Microsoft, National Semiconductor – OHCI - Open Host Controller Interface (transfer most of the effort to the electronic controller, simplifying the driver software (driver)) • 2.0 – EHCI - Enhanced Host Controller Interface (combines quality of the two models with a greater bandwidth) Device Classes • USB defines class codes used to identify a device’s functionality and to load a device driver based on that functionality Class Usage Description Examples 00h Device Unspecifiedclass 0 (Device class is unspecified. Interface descriptors are used for determining the required drivers.) 01h 02h 03h 05h Interface Both Interface Interface Audio Communications and CDC Control Human Interface Device (HID) Physical Interface Device (PID) Speaker, microphone, sound card Ethernet adapter, modem, serial port adapter Keyboard, mouse, joystick Force feedback joystick 06h Interface Image Digital camera (Most cameras function as Mass Storage for direct access to storage media). 07h Interface Printer Laser printer, Inkjet printer 08h Interface Mass Storage USB flash drive, memory card reader, digital audio player, external drives 09h Device USB hub Full speed hub, hi-speed hub 0Ah Interface CDC-Data (This class is used together with class 02h - Communications and CDC Control.) 0Bh 0Dh 0Eh 0Fh DCh E0h EFh FEh Interface Interface Interface Interface Both Interface Both Interface Smart Card Content Security Video Personal Healthcare Diagnostic Device Wireless Controller Miscellaneous Application Specific USB smart card reader Webcam USB compliance testing device Wi-Fi adapter, Bluetooth adapter ActiveSync device IrDA Bridge FFh Both Vendor Specific (This class code indicates that the device needs vendor specific drivers.) USB Connectors Cable • The maximum length of a standard USB cable is 3.0 meters (1.1) or 5.0 meters (2.0) • Maximum hubs connected in series is 5 • Maximum distance of 30 meters between host and device - because of the delay • The data cables are a Twisted pair to reduce noise and crosstalk Miniplug/Microplug Pin Name Cable color Description 1 VCC Red +5V 2 D− White Data − 3 D+ Green Data + 4 GND Black Ground Pin Name Color Description 1 VCC Red +5 V 2 D− White Data − 3 D+ Green Data + 4 ID none permits distinction of Micro-A- and Micro-BPlug Type A: connected to Ground Type B: not connected 5 GND Black Signal Ground USB Versions • USB 0.7: Released in November 1994 • USB 0.8: Released in December 1994 • USB 0.9: Released in April 1995 • USB 0.99: Released in August 1995 • USB 1.0: Released in January 1996, with data transfer rates of 1.5 Mbit / s • USB 1.1: Released in 1998 • USB 2.0: Released in April 2000 USB 1.1 • Specified data rates of 1.5 Mbit/s (Low-Speed) and 12 Mbit/s (Full- Speed) • Standard interface • Fixed problems identified in 1.0, mostly relating to hubs • Used for small peripherals USB 2.0 • Added higher maximum speed of 480 Mbit/s (now called Hi-Speed) • Uses the same standart connector • Compatible with 1.1 devices but with reduced speed • Manufacturers could adopt the standard into their products without the obligation to pay a license to use the technology • There was an increase in the range of possibilities because of the hispeed USB 3.0 • A SuperSpeed rate of 5.0 Gbit/s, 10 times faster than 2.0 • Products using the 3.0 specification are likely to arrive in 2009 or 2010 • The trade name will be SuperSpeed USB • The technology is similar to PCI Express 2.0 (5-Gbit/s) - comparing the cables Applications and Utilities [email protected]