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Historical Perspective

Historical Perspective. The Universal Serial Bus was originally developed in 1995 by a group of industry leading companies Compaq, Hewlett Packard, Intel, Lucent, Microsoft, NEC and Philips were involved in USB 2 developments

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Historical Perspective

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  1. Historical Perspective • The Universal Serial Bus was originally developed in 1995 by a group of industry leading companies • Compaq, Hewlett Packard, Intel, Lucent, Microsoft, NEC and Philips were involved in USB 2 developments • USB defines an external expansion bus which makes adding peripherals to a PC relatively easy • See: http://www.everythingusb.com/

  2. Historical Perspective • Major goals of USB 1.0 were ease-of-use and low cost • USB version 1 was not designed to be a high speed bus – it’s for mice, keyboards, printers, scanners etc. • In 2006, Intel estimated that over 3.5 billion USB interfaces had shipped • NB that may include 2-10 “interfaces” per PC!

  3. USB Connections • The external expansion architecture of USB is shown below, which highlights: • PC host controller hardware and software • Robust connectors and cable assemblies • “Peripheral friendly” master-slave protocols • Expandable through multi-port hubs

  4. Role of USB h/w and s/w • Uniform view of I/O system for all application software • Hides hardware implementation details • Manages the dynamic attachment and detachment of peripherals • “Enumeration” – initial communication with peripherals to discover device and driver identity • Unique “address” for each peripheral • Host PC software incorporates attached peripherals into the system power management scheme

  5. Role of USB1.1 Hubs • Provides additional, bi-directional connectivity for USB peripherals and works as bi-directional repeater • Provides managed power to attached peripherals • Recognises dynamic attachment of a peripheral • Provides power during initialisation and later (0.5W to 2.5W max) • May be cascaded up to five levels deep • Monitors signals and handles transactions addressed to itself • Supports 12Mbps (full-speed) and 1.5Mbps (low-speed) peripherals

  6. USB1.1 Peripherals • All USB peripherals are uniform slave devices that obey a defined protocol • Peripherals respond to control transactions which • may request detailed information about the device • may request device configuration information • may allocate a device ID • Peripherals send and receive data to/from the host using a standard USB data format • Standardized data movement to/from the PC host gives USB great flexibility and simplicity

  7. USB 2.0 • Same cables, same software interfaces, full support for USB1.1 devices • Plus support for high-speed devices up to 480Mbits/sec • Hub complexity increased to handle situations intelligently • Became available some time after mid-2000

  8. Wireless USB • High speed personal wireless interconnect technology • Connects up to 127 devices • Up to 480Mbps at 3 metres • Up to 110Mbps at 10 metres • Based on the WiMedia Alliance “ultra-wideband common radio platform” • See http://www.usb.org/developers/wusb/docs/wirelessUSB.pdf

  9. USB 3.0 • Released: End of 2008 • USB 3.0 Promoters Group members:Intel, Microsoft, Hewlett-Packard, Texas Instruments, NEC and NXP Semiconductors • Products started arriving in early 2010 • 4.8Gbps (625MB/s), originally intended to be an optical and copper connection, backwards compatible with USB2 • Actually just a copper connection – cheaper and easier to make than optical • No one expected copper cabling to support 4.8Gbps in full duplex mode (USB 2 is only half-duplex) • More energy efficient protocols and transmission than USB2

  10. USB On-The-Go • Normally, communication is controlled by a PC • There is no way to connect peripherals together without the PC • The USB On-The-Go (OTG) initiative specifies some additional capabilities to USB2.0 • It adds some host capabilities to USB peripherals for direct interconnection • Makes USB a bit more like FireWire • See http://www.usb.org/developers/onthego/USB_OTG_Intro.pdf

  11. Why USB? • Changes to PC design are reducing internal expansion capability • Ease of use – relatively simple for the user • Better than existing connectors (2S/1P…) • Good backwards compatibility, protecting investments • Supported by many platforms (phones, CD players…) • Single standard for manufacturers • Design time will be reduced after initial learning period, broadens market • Cost to manufacturers reduced by standardisation but initially raised by added complexity • See: http://www.techrepublic.com/blog/10things/10-things-you-should-know-about-usb-20-and-30/1265

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