Embed Size (px)
Citation preview
Universal Serial Bus - USBHistorical PerspectiveThe 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/
Universal Serial Bus - USBHistorical PerspectiveMajor 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 shippedNB that may include 2-10 “interfaces” per PC!
Universal Serial Bus - USBUSB ConnectionsThe external expansion architecture of USB is shown
below, which highlights:
PC host controller hardware and softwareRobust connectors and cable assemblies“Peripheral friendly” master-slave protocolsExpandable through multi-port hubs
Universal Serial Bus - USBRole of USB h/w and s/wUniform 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
Universal Serial Bus - USBRole of USB1.1 HubsProvides 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
Universal Serial Bus - USBUSB1.1 PeripheralsAll USB peripherals are uniform slave devices that
obey a defined protocol
Peripherals respond to control transactions whichmay request detailed information about the devicemay request device configuration informationmay 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
Universal Serial Bus - USBUSB 2.0Same cables, same software interfaces, full support
for USB1.1 devicesPlus support for high-speed devices up to 480Mbits/secHub complexity increased to handle situations intelligentlyBecame available some time after mid-2000
Universal Serial Bus - USBWireless USBHigh 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
Universal Serial Bus - USBUSB 3.0Released: 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
Universal Serial Bus - USBUSB 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
Universal Serial Bus - USBWhy USB?Changes to PC design are reducing internal expansion
capability
Ease of use – relatively simple for the userBetter than existing connectors (2S/1P…)Good backwards compatibility, protecting investmentsSupported by many platforms (phones, CD players…)
Single standard for manufacturersDesign time will be reduced after initial learning period,
broadens marketCost 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
