For the portable USB storage device, see USB flash drive. For other uses, see USB (disambiguation).
Certified USB logo
|Designer||Compaq, DEC, IBM, Intel, Microsoft, NEC, and Nortel|
|Designed||January 1996; 22 years ago (1996-01)|
|Produced||Since May 1996|
|Superseded||Serial port, parallel port, game port, Apple Desktop Bus, PS/2 port, and MagSafe|
|Length||2–5 m (6 ft 7 in–16 ft 5 in) (by category)|
|Signal||5 V DC|
|Data signal||Packet data, defined by specifications|
|Bitrate||1.5, 12, 480, 5,000, 10,000, 20,000 Mbit/s (depending on mode)|
|The type-A plug (left) and type-B plug (right)|
|Pin 1||VBUS (+5 V)|
USB, short for Universal Serial Bus, is an industry standard that was developed to define cables, connectors and protocols for connection, communication, and power supply between personal computers and their peripheral devices. 
USB was designed to standardize the connection of computer peripherals (including keyboards, pointing devices, digital cameras, printers, portable media players, disk drives and network adapters) to personal computers, both to communicate and to supply electric power. It has largely replaced interfaces such as serial ports and parallel ports, and has become commonplace on a wide range of devices. USB connectors have replaced other types for battery chargers of portable devices.
Released in 1996, the USB standard is currently maintained by the USB Implementers Forum (USB IF).
The three sizes of USB connectors are the default or standard format intended for desktop or portable equipment, the mini intended for mobile equipment , and the thinner micro size, for low-profile mobile equipment such as mobile phones and tablets. There are five speeds for USB data transfer: Low Speed, Full Speed, High Speed (from version 2.0 of the specification), SuperSpeed (from version 3.0), and SuperSpeed+ (from version 3.1). The modes have differing hardware and cabling requirements. USB devices have some choice of implemented modes, and USB version is not a reliable statement of implemented modes. Modes are identified by their names and icons, and the specifications suggests that plugs and receptacles be colour-coded (SuperSpeed is identified by blue).
Unlike other data buses (such as Ethernet), USB connections are directed; a host device has "downstream" facing ports that that connect to the "upstream" ports of devices. Only downstream facing ports provide power; this topology was chosen to easily prevent electrical overloads and damaged equipment. Thus, USB cables have different ends: A and B, with different physical connectors for each. Each format has a plug and receptacle defined for each of the A and B ends. USB cables have plugs, and the corresponding receptacles are on the computers or electronic devices. In common practice, the A end is usually the standard format, and the B side varies over standard, mini, and micro. The mini and micro formats also provide for USB On-The-Go with a hermaphroditic AB receptacle, which accepts either an A or a B plug. On-The-Go allows USB between peers without discarding the directed topology by choosing the host at connection time; it also allows one receptacle to perform double duty in space-constrained applications.
There are cables with A plugs on both ends, which may be valid if the cable includes, for example, a USB host-to-host transfer device with 2 ports.
The micro format has the highest designed insertion lifetime. The standard and mini connectors have a design lifetime of 1,500 insertion-removal cycles, the improved Mini-B connectors increased this to 5,000. The micro connectors were designed with frequent charging of portable devices in mind, so have a design life of 10,000 cycles and also place the flexible contacts, which wear out sooner, on the easily replaced cable, while the more durable rigid contacts are located in the receptacles. Likewise, the springy component of the retention mechanism, parts that provide required gripping force, were also moved into plugs on the cable side.
A group of seven companies began the development of USB in 1994: Compaq, DEC, IBM, Intel, Microsoft, NEC, and Nortel. The goal was to make it fundamentally easier to connect external devices to PCs by replacing the multitude of connectors at the back of PCs, addressing the usability issues of existing interfaces, and simplifying software configuration of all devices connected to USB, as well as permitting greater data rates for external devices. A team including Ajay Bhatt worked on the standard at Intel; the first integrated circuits supporting USB were produced by Intel in 1995.
The original USB 1.0 specification, which was introduced in January 1996, defined data transfer rates of 1.5 Mbit/sLow Speed and 12 Mbit/s Full Speed. Microsoft Windows 95, OSR 2.1 provided OEM support for the devices. The first widely used version of USB was 1.1, which was released in September 1998. The 12 Mbit/s data rate was intended for higher-speed devices such as disk drives, and the lower 1.5 Mbit/s rate for low data rate devices such as joysticks.Apple Inc.'s iMac was the first mainstream product with USB and the iMac's success popularized USB itself. Following Apple's design decision to remove all legacy ports from the iMac, many PC manufacturers began building legacy-free PCs, which led to the broader PC market using USB as a standard.
The USB 2.0 specification was released in April 2000 and was ratified by the USB Implementers Forum (USB-IF) at the end of 2001. Hewlett-Packard, Intel, Lucent Technologies (now Nokia), NEC, and Philips jointly led the initiative to develop a higher data transfer rate, with the resulting specification achieving 480 Mbit/s, 40 times as fast as the original USB 1.1 specification.
The USB 3.0 specification was published on 12 November 2008. Its main goals were to increase the data transfer rate (up to 5 Gbit/s), decrease power consumption, increase power output, and be backward compatible with USB 2.0. USB 3.0 includes a new, higher speed bus called SuperSpeed in parallel with the USB 2.0 bus. For this reason, the new version is also called SuperSpeed. The first USB 3.0 equipped devices were presented in January 2010.
As of 2008[update], approximately 6 billion USB ports and interfaces were in the global marketplace, and about 2 billion were being sold each year.
The USB 3.1 specification was published in July 2013.
In December 2014, USB-IF submitted USB 3.1, USB Power Delivery 2.0 and USB Type-C specifications to the IEC (TC 100 – Audio, video and multimedia systems and equipment) for inclusion in the international standard IEC 62680 Universal Serial Bus interfaces for data and power, which is currently based on USB 2.0.
The USB 3.2 specification was published in September 2017.
Version history 
|Release name||Release date||Maximum transfer rate||Note|
|USB 0.8||December 1994||Prerelease|
|USB 0.9||April 1995||Prerelease|
|USB 0.99||August 1995||Prerelease|
|USB 1.0-RC||November 1995||Release Candidate|
|USB 1.0||January 1996||Full Speed (12 Mbit/s)|
|USB 1.1||August 1998||Full Speed (12 Mbit/s)|
|USB 2.0||April 2000||High Speed (480 Mbit/s)|
|USB 3.0||November 2008||SuperSpeed (5 Gbit/s)||Also referred to as USB 3.1 Gen 1 and USB 3.2 Gen 1x1|
|USB 3.1||July 2013||SuperSpeed+ (10 Gbit/s)||Also referred to as USB 3.1 Gen 2  and USB 3.2 Gen 2x1|
|USB 3.2||September 2017||SuperSpeed+ (20 Gbit/s)||Includes new USB 3.2 Gen 1x2 and USB 3.2 Gen 2x2 multi-link modes [not in citation given]|
|Release name||Release date||Max. power||Note|
|USB Battery Charging 1.0||2007-03-08||5 V, 1.5 A|
|USB Battery Charging 1.1||2009-04-15|
|USB Battery Charging 1.2||2010-12-07||5 V, 5 A|
|USB Power Delivery revision 1.0 (version 1.0)||2012-07-05||20 V, 5 A||Using FSK protocol over bus power (VBUS)|
|USB Power Delivery revision 1.0 (version 1.3)||2014-03-11|
|USB Type-C 1.0||2014-08-11||5 V, 3 A||New connector and cable specification|
|USB Power Delivery revision 2.0 (version 1.0)||2014-08-11||20 V, 5 A||Using BMC protocol over communication channel (CC) on type-C cables.|
|USB Type-C 1.1||2015-04-03||5 V, 3 A|
|USB Power Delivery revision 2.0 (version 1.1)||2015-05-07||20 V, 5 A|
|USB Power Delivery revision 2.0 (version 1.2)||2016-03-25||20 V, 5 A|
|USB Power Delivery revision 3.0 (version 1.1)||2017-01-12||20 V, 5 A|
Released in January 1996, USB 1.0 specified data rates of 1.5 Mbit/s (Low Bandwidth or Low Speed) and 12 Mbit/s (Full Speed). It did not allow for extension cables or pass-through monitors, due to timing and power limitations. Few USB devices made it to the market until USB 1.1 was released in August 1998. USB 1.1 was the earliest revision that was widely adopted and led to what Microsoft designated the "Legacy-free PC".
Neither USB 1.0 nor 1.1 specified a design for any connector smaller than the standard type A or type B. Though many designs for a miniaturised type B connector appeared on many peripherals, conformance to the USB 1.x standard was fudged by treating peripherals that had miniature connectors as though they had a tethered connection (that is: no plug or socket at the peripheral end). There was no known miniature type A connector until USB 2.0 (rev 1.01) introduced one.
USB 2.0 was released in April 2000, adding a higher maximum signaling rate of 480 Mbit/s (High Speed or High Bandwidth), in addition to the USB 1.x Full Speed signaling rate of 12 Mbit/s. Due to bus access constraints, the effective throughput of the High Speed signaling rate is limited to 280 Mbit/s or 35 MB/s.
Further modifications to the USB specification have been made via Engineering Change Notices (ECN). The most important of these ECNs are included into the USB 2.0 specification package available from USB.org:
- Mini-A and Mini-B Connector ECN: Released in October 2000.
- Specifications for Mini-A and Mini-B plug and receptacle. Also receptacle that accepts both plugs for On-The-Go. These should not be confused with Micro-B plug and receptacle.
- Pull-up/Pull-down Resistors ECN: Released in May 2002.
- Interface Associations ECN: Released in May 2003.
- New standard descriptor was added that allows associating multiple interfaces with a single device function.
- Rounded Chamfer ECN: Released in October 2003.
- A recommended, backward compatible change to Mini-B plugs that results in longer lasting connectors.
- Unicode ECN: Released in February 2005.
- This ECN specifies that strings are encoded using UTF-16LE. USB 2.0 specified Unicode, but did not specify the encoding.
- Inter-Chip USB Supplement: Released in March 2006.
- On-The-Go Supplement 1.3: Released in December 2006.
- USB On-The-Go makes it possible for two USB devices to communicate with each other without requiring a separate USB host. In practice, one of the USB devices acts as a host for the other device.
- Battery Charging Specification 1.1: Released in March 2007 and updated on 15 April 2009.
- Adds support for dedicated chargers (power supplies with USB connectors), host chargers (USB hosts that can act as chargers) and the No Dead Battery provision, which allows devices to temporarily draw 100 mA current after they have been attached. If a USB device is connected to a dedicated charger, maximum current drawn by the device may be as high as 1.8 A. (This document is distributed with the USB 3.0 and USB On-The-Go. specification packages)
- Micro-USB Cables and Connectors Specification 1.01: Released in April 2007.
- Link Power Management Addendum ECN: Released in July 2007.
- This adds sleep, a new power state between enabled and suspended states. Device in this state is not required to reduce its power consumption. However, switching between enabled and sleep states is much faster than switching between enabled and suspended states, which allows devices to sleep while idle.
- Battery Charging Specification 1.2: Released in December 2010.
- Several changes and increasing limits including allowing 1.5 A on charging ports for unconfigured devices, allowing High Speed communication while having a current up to 1.5 A and allowing a maximum current of 5 A.
Main article: USB 3.0
The USB 3.0 specification was released on 12 November 2008, with its management transferring from USB 3.0 Promoter Group to the USB Implementers Forum (USB-IF), and announced on 17 November 2008 at the SuperSpeed USB Developers Conference.
USB 3.0 adds a SuperSpeed transfer mode, with associated backward compatible plugs, receptacles, and cables. SuperSpeed plugs and receptacles are identified with a distinct logo and blue inserts in standard format receptacles.
The SuperSpeed mode provides a data signaling rate of 5.0 Gbit/s. However, due to the overhead incurred by 8b/10b encoding, the payload throughput is actually 4 Gbit/s, and the specification considers it reasonable to achieve about 3.2 Gbit/s (0.4 GB/s or 400 MB/s). Communication is full-duplex in SuperSpeed transfer mode; earlier modes are half-duplex, arbitrated by the host.
Low-power and high-power devices remain operational with this standard, but devices using SuperSpeed can take advantage of increased available current of between 150 mA and 900 mA, respectively.
A USB system consists of a host with one or more downstream ports, and multiple peripherals, forming a tiered-star topology. Additional USB hubs may be included, allowing up to five tiers. A USB host may have multiple controllers, each with one or more ports. Up to 127 devices may be connected to a single host controller. USB devices are linked in series through hubs. The hub built into the host controller is the root hub.
A USB device may consist of several logical sub-devices that are referred to as device functions. A composite device may provide several functions, for example, a webcam (video device function) with a built-in microphone (audio device function). An alternative to this is compound device, in which the host assigns each logical device a distinctive address and all logical devices connect to a built-in hub that connects to the physical USB cable.
USB device communication is based on pipes (logical channels). A pipe is a connection from the host controller to a logical entity, found on a device, and named an endpoint. Because pipes correspond to endpoints, the terms are sometimes used interchangeably. A USB device could have up to 32 endpoints (16 IN, 16 OUT), though it is rare to have so many. An endpoint is defined and numbered by the device during initialization (the period after physical connection called "enumeration") and so is relatively permanent, whereas a pipe may be opened and closed.
There are two types of pipe: stream and message. A message pipe is bi-directional and is used for control transfers. Message pipes are typically used for short, simple commands to the device, and a status response, used, for example, by the bus control pipe number 0. A stream pipe is a uni-directional pipe connected to a uni-directional endpoint that transfers data using an isochronous,interrupt, or bulk transfer:
- Isochronous transfers
- At some guaranteed data rate (often, but not necessarily, as fast as possible) but with possible data loss (e.g., realtime audio or video)
- Interrupt transfers
- Devices that need guaranteed quick responses (bounded latency) (e.g., pointing devices and keyboards)
- Bulk transfers
- Large sporadic transfers using all remaining available bandwidth, but with no guarantees on bandwidth or latency (e.g., file transfers)
When a host starts a data transfer, it sends a TOKEN packet containing an endpoint specified with a tuple of (device_address, endpoint_number). If the transfer is from the host to the endpoint, the host sends an OUT packet (a specialization of a TOKEN packet) with the desired device address and endpoint number. If the data transfer is from the device to the host, the host sends an IN packet instead. If the destination endpoint is a uni-directional endpoint whose manufacturer's designated direction does not match the TOKEN packet (e.g. the manufacturer's designated direction is IN while the TOKEN packet is an OUT packet), the TOKEN packet is ignored. Otherwise, it is accepted and the data transaction can start. A bi-directional endpoint, on the other hand, accepts both IN and OUT packets.
Endpoints are grouped into interfaces and each interface is associated with a single device function. An exception to this is endpoint zero, which is used for device configuration and is not associated with any interface. A single device function composed of independently controlled interfaces is called a composite device. A composite device only has a single device address because the host only assigns a device address to a function.
When a USB device is first connected to a USB host, the USB device enumeration process is started. The enumeration starts by sending a reset signal to the USB device. The data rate of the USB device is determined during the reset signaling. After reset, the USB device's information is read by the host and the device is assigned a unique 7-bit address. If the device is supported by the host, the device drivers needed for communicating with the device are loaded and the device is set to a configured state. If the USB host is restarted, the enumeration process is repeated for all connected devices.
The host controller directs traffic flow to devices, so no USB device can transfer any data on the bus without an explicit request from the host controller. In USB 2.0, the host controller polls the bus for traffic, usually in a round-robin fashion. The throughput of each USB port is determined by the slower speed of either the USB port or the USB device connected to the port.
High-speed USB 2.0 hubs contain devices called transaction translators that convert between high-speed USB 2.0 buses and full and low speed buses. There may be one translator per hub or per port.
Because there are two separate controllers in each USB 3.0 host, USB 3.0 devices transmit and receive at USB 3.0 data rates regardless of USB 2.0 or earlier devices connected to that host. Operating data rates for earlier devices are set in the legacy manner.
The functionality of a USB device is defined by a class code sent to a USB host. This allows the host to load software modules for the device and to support new devices from different manufacturers.
Device classes include:
|Class||Usage||Description||Examples, or exception|
|00h||Device||Unspecified||Device class is unspecified, interface descriptors are used to determine needed drivers|
|01h||Interface||Audio||Speaker, microphone, sound card, MIDI|
|02h||Both||Communications and CDC Control||Modem, Ethernet adapter, Wi-Fi adapter, RS232serial adapter. Used together with class 0Ah (below)|
|03h||Interface||Human interface device (HID)||Keyboard, mouse, joystick|
|05h||Interface||Physical Interface Device (PID)||Force feedback joystick|
|06h||Interface||Image (PTP/MTP)||Webcam, scanner|
|07h||Interface||Printer||Laser printer, inkjet printer, CNC machine|
|08h||Interface||Mass storage (MSC or UMS)||USB flash drive, memory cardreader, digital audio player, digital camera, external drive|
|09h||Device||USB hub||Full bandwidth hub|
|0Ah||Interface||CDC-Data||Used together with class 02h (above)|
|0Bh||Interface||Smart Card||USB smart card reader|
|0Dh||Interface||Content security||Fingerprint reader|
|0Fh||Interface||Personal healthcare device class (PHDC)||Pulse monitor (watch)|
|10h||Interface||Audio/Video (AV)||Webcam, TV|
|11h||Device||Billboard||Describes USB Type-C alternate modes supported by device|
|DCh||Both||Diagnostic Device||USB compliance testing device|
|E0h||Interface||Wireless Controller||Bluetooth adapter, Microsoft RNDIS|
|FEh||Interface||Application-specific||IrDA Bridge, Test & Measurement Class (USBTMC), USB DFU (Device Firmware Upgrade)|
|FFh||Both||Vendor-specific||Indicates that a device needs vendor-specific drivers|
USB mass storage / USB drive
See also: USB mass storage device class, Disk enclosure, and External hard disk drive
USB mass storage device class (MSC or UMS) standardizes connections to storage devices. At first intended for magnetic and optical drives, it has been extended to support flash drives. It has also been extended to support a wide variety of novel devices as many systems can be controlled with the familiar metaphor of file manipulation within directories. The process of making a novel device look like a familiar device is also known as extension. The ability to boot a write-locked SD card with a USB adapter is particularly advantageous for maintaining the integrity and non-corruptible, pristine state of the booting medium.
Though most personal computers since mid-2004 can boot from USB mass storage devices, USB is not intended as a primary bus for a computer's internal storage. . However, USB has the advantage of allowing hot-swapping, making it useful for mobile peripherals, including drives of various kinds.
First conceived and still used today for optical storage devices (CD-RW drives, DVD drives, etc.), several manufacturers offer external portable USB hard disk drives, or empty enclosures for disk drives. These offer performance comparable to internal drives, limited by the current number and types of attached USB devices, and by the upper limit of the USB interface. Other competing standards for external drive connectivity include eSATA, ExpressCard, FireWire (IEEE 1394), and most recently Thunderbolt.
Another use for USB mass storage devices is the portable execution of software applications (such as web browsers and VoIP clients) with no need to install them on the host computer.
Media Transfer Protocol
See also: Picture Transfer Protocol
Media Transfer Protocol (MTP) was designed by Microsoft to give higher-level access to a device's filesystem than USB mass storage, at the level of files rather than disk blocks. It also has optional DRM features. MTP was designed for use with portable media players, but it has since been adopted as the primary storage access protocol of the Android operating system from the version 4.1 Jelly Bean as well as Windows Phone 8 (Windows Phone 7 devices had used the Zune protocol—an evolution of MTP). The primary reason for this is that MTP does not require exclusive access to the storage device the way UMS does, alleviating potential problems should an Android program request the storage while it is attached to a computer. The main drawback is that MTP is not as well supported outside of Windows operating systems.
Human interface devices
Main article: USB human interface device class
Joysticks, keypads, tablets and other human-interface devices (HIDs) are also progressively[when?] migrating from MIDI, and PC game port connectors to USB.
USB mice and keyboards can usually be used with older computers that have PS/2 connectors with the aid of a small USB-to-PS/2 adapter. For mice and keyboards with dual-protocol support, an adaptor that contains no logic circuitry may be used: the hardware in the USB keyboard or mouse is designed to detect whether it is connected to a USB or PS/2 port, and communicate using the appropriate protocol. Converters also exist that connect PS/2 keyboards and mice (usually one of each) to a USB port. These devices present two HID endpoints to the system and use a microcontroller to perform bidirectional data translation between the two standards.
Device Firmware Upgrade
Device Firmware Upgrade (DFU) is a vendor- and device-independent mechanism for upgrading the firmware of USB devices with improved versions provided by their manufacturers, offering (for example) a way to deploy firmware bug fixes. During the firmware upgrade operation, USB devices change their operating mode effectively becoming a PROM programmer. Any class of USB device can implement this capability by following the official DFU specifications.
In addition to its intended legitimate purposes, DFU can also be exploited by uploading maliciously crafted firmware that causes USB devices to spoof various other device types; one such exploiting approach is known as BadUSB.
The connectors the USB committee specifies support a number of USB's underlying goals, and reflect lessons learned from the many connectors the computer industry has used. The female connector mounted on the host or device is called the receptacle, and the male connector attached to the cable is called the plug. T
By design, it is difficult to insert a USB plug into its receptacle incorrectly. The USB specification requires that the cable plug and receptacle be marked so the user can recognize the proper orientation.  The type-C plug is reversible. USB cables and small USB devices are held in place by the gripping force from the receptacle, with no screws, clips, or thumb-turns as other connectors use.
The different A and B plugs prevent accidentally connecting two power sources. However, some of this directed topology is lost with the advent of multi-purpose USB connections (such as USB On-The-Go in smartphones, and USB-powered Wi-Fi routers), which require A-to-A, B-to-B, and sometimes Y/splitter cables. See the USB On-The-Go connectors section below for a more detailed summary description.
The standard connectors were designed to be more robust than many past connectors. This is because USB is hot-pluggable, and the connectors would be used more frequently, and perhaps with less care, than previous connectors.
Standard USB has a minimum rated lifetime of 1,500 cycles of insertion and removal, the mini-USB receptacle increases this to 5,000 cycles, and the newer Micro-USB and USB-C receptacles are both designed for a minimum rated lifetime of 10,000 cycles of insertion and removal. To accomplish this, a locking device was added and the leaf-spring was moved from the jack to the plug, so that the most-stressed part is on the cable side of the connection. This change was made so that the connector on the less expensive cable would bear the most wear.
In standard USB, the electrical contacts in a USB connector are protected by an adjacent plastic tongue, and the entire connecting assembly is usually protected by an enclosing metal shell.
The shell on the plug makes contact with the receptacle before any of the internal pins. The shell is typically grounded, to dissipate static electricity and to shield the wires within the connector.
The USB standard specifies tolerances for compliant USB connectors to minimize physical incompatibilities in connectors from different vendors. The USB specification also defines limits to the size of a connecting device in the area around its plug, so that adjacent ports are not blocked. Compliant devices must either fit within the size restrictions or support a compliant extension cable that does.
USB connector types multiplied as the specification progressed. The original USB specification detailed standard-A and standard-B plugs and receptacles.The connectors were different so that users could not connect one computer receptacle to another. The data pins in the standard plugs are recessed compared to the power pins,so that the device can power up before establishing a data connection. Some devices operate in different modes depending on whether the data connection is made. Charging docks supply power and do not include a host device or data pins, allowing any capable USB device to charge or operate from a standard USB cable. Charging cables provide power connections, but not data. In a charge-only cable, the data wires are shorted at the device end, otherwise the device may reject the charger as unsuitable.
The type-A plug has an elongated rectangular cross-section, inserts into a type-A receptacle on a downstream port on a USB host or hub, and carries both power and data. Captive cables on USB devices, such as keyboards or mice, terminate with a type-A plug.
The type-B plug has a near square cross-section with the top exterior corners beveled. As part of a removable cable, it inserts into an upstream port on a device, such as a printer. On some devices, the type-B receptacle has no data connections, being used solely for accepting power from the upstream device. This two-connector-type scheme (A/B) prevents a user from accidentally creating a loop.
The maximum allowed cross-section of the overmold boot (which is part of the connector used for its handling) is 16 by 8 mm (0.63 by 0.31 in) for the standard-A plug type, while for the type-B it is 11.5 by 10.5 mm (0.45 by 0.41 in).
Mini-USB connectors were introduced together with USB 2.0 in April 2000, for use with smaller devices such as digital cameras, smartphones, and tablet computers. The Mini-A connector and the Mini-AB receptacle connector have been deprecated since May 2007. Mini-B connectors are still supported, but are not On-The-Go-compliant; the Mini-B USB connector was standard for transferring data to and from the early smartphones and PDAs. Both Mini-A and Mini-B plugs are approximately 3 by 7 mm (0.12 by 0.28 in).
Micro-USB connectors, which were announced by the USB-IF on 4 January 2007, have a similar width to Mini-USB, but approximately half the thickness, enabling their integration into thinner portable devices. The Micro-A connector is 6.85 by 1.8 mm (0.270 by 0.071 in) with a maximum overmold boot size of 11.7 by 8.5 mm (0.46 by 0.33 in), while the Micro-B connector is 6.85 by 1.8 mm (0.270 by 0.071 in) with a maximum overmold size of 10.6 by 8.5 mm (0.42 by 0.33 in).
The thinner Micro-USB connectors were introduced to replace the Mini connectors in devices manufactured since May 2007, including smartphones, personal digital assistants, and cameras.
The Micro plug design is rated for at least 10,000 connect-disconnect cycles, which is more than the Mini plug design. The Micro connector is also designed to reduce the mechanical wear on the device; instead the easier-to-replace cable is designed to bear the mechanical wear of connection and disconnection. The Universal Serial Bus Micro-USB Cables and Connectors Specification details the mechanical characteristics of Micro-A plugs, Micro-AB receptacles (which accept both Micro-A and Micro-B plugs),Double-Sided Micro USB, and Micro-B plugs and receptacles, along with a standard-A receptacle to Micro-A plug adapter.
Micro-USB was endorsed as the standard connector for data and power on mobile devices by the cellular phone carrier group Open Mobile Terminal Platform (OMTP) in 2007.
Micro-USB was embraced as the "Universal Charging Solution" by the International Telecommunication Union (ITU) in October 2009.
In Europe, micro-USB became the defined common external power supply (EPS) for use with smartphones sold in the EU, 14 of the world's largest mobile phone manufacturers signed the EU's common EPS Memorandum of Understanding (MoU).Apple, one of the original MoU signers, makes Micro-USB adapters available – as permitted in the Common EPS MoU – for its iPhones equipped with Apple's proprietary 30-pin dock connector or (later) Lightning connector. according to the CEN, CENELEC, and ETSI.
USB 3.0 connectors and backward compatibility
See also: USB 3.0 § Connectors
USB 3.0 introduced Type-A SuperSpeed plugs and receptacles as well as micro-sized Type-B SuperSpeed plugs and receptacles. The 3.0 receptacles are backward-compatible with the corresponding pre-3.0 plugs.
USB 3.0 and USB 1.0 Type-A plugs and receptacles are designed to interoperate. To achieve USB 3.0's SuperSpeed (and SuperSpeed+ for USB 3.1 Gen 2), 5 extra pins are added to the unused area of the original 4 pin USB 1.0 design, making USB 3.0 Type-A plugs and receptacles backward compatible to those of USB 1.0.
On the device side, a modified Micro-B plug (Micro-B SuperSpeed) is used to cater for the five additional pins required to achieve the USB 3.0 features (USB Type-C plug can also be used). The USB 3.0 Micro-B plug effectively consists of a standard USB 2.0 Micro-B cable plug, with an additional 5 pins plug "stacked" to the side of it. In this way, cables with smaller 5 pin USB 2.0 Micro-B plugs can be plugged into devices with 10 contact USB 3.0 Micro-B receptacles and achieve backward compatibility.
USB cables exist with various combinations of plugs on each end of the cable, as displayed below in the USB cables matrix.
USB On-The-Go connectors
Main article: USB On-The-Go
USB On-The-Go (OTG) introduces the concept of a device performing both master and slave roles. All current OTG devices are required to have one, and only one, USB connector: a Micro-AB receptacle. (In the past, before the development of Micro-USB, On-The-Go devices used Mini-AB receptacles).
The Micro-AB receptacle is capable of accepting both Micro-A and Micro-B plugs, attached to any of the legal cables and adapters as defined in revision 1.01 of the Micro-USB specification.
To enable Type-AB receptacles to distinguish which end of a cable is plugged in, plugs have an "ID" pin in addition to the four contacts in standard-size USB connectors. This ID pin is connected to GND in Type-A plugs, and left unconnected in Type-B plugs. Typically, a pull-up resistor in the device is used to detect the presence or absence of an ID connection.
The OTG device with the A-plug inserted is called the A-device and is responsible for powering the USB interface when required, and by default assumes the role of host. The OTG device with the B-plug inserted is called the B-device and by default assumes the role of peripheral. An OTG device with no plug inserted defaults to acting as a B-device. If an application on the B-device requires the role of host, then the Host Negotiation Protocol (HNP) is used to temporarily transfer the host role to the B-device.
OTG devices attached either to a peripheral-only B-device or a standard/embedded host have their role fixed by the cable, since in these scenarios it is only possible to attach the cable one way.
- Micro-B plug
- Mini-B plug
- type-A receptacle[c]
- type-A plug
- type-B plug
- ^The VBUS supply from a low-powered hub port may drop to 4.40 V.
- ^UC-E6 is a proprietary non-USB connector.
- ^Inverted, so the contacts are visible.
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- Canon 350D, 400D, 450D, 500D, 550D, 60D, Pentax manual shutter/focus control The external trigger can be accessed with a standard 3-pole 2.5 mm jack plug. Appropriate 'official' remote controller with this plug is called RS-60 E3 or COS-60E3. The same pinout is used by all Pentax cameras
- Canon DSLR 300D, 350D, 400D, 450D, 500D computer manual shooter control serial cable used for computerized long exposure control
- Canon EF-S lens connector Canon EFS lenses are connected to the body via a 7 pin connector
- Canon N3 manual shooter / focus for EOS 10D, 20D, 30D, 40D, 50D, 5D, 5Dmk2, 7D connector with N3 connector. The connector may be obtained from wired remote control
- Canon STV-250N Audio/Video Cable Pinout for Canon STV-250N (AV Cable)
- Kodak camera serial cable This is the layout of the Kodak digital camera interface cable to a pc serial port, (used by KODAK DC40, DC50, DC120, DC240, DC280, DC3400, DC5000, RCA CDS4100, VIVITAR 3500, ROLLEI Model D7COM) to download the stored images from camera to pc.
- Kodak Easyshare 6000 camera dock Pinouts of Kodak digital camera dock connector. Some digital cameras (e.g. Kodak CX7300) don?t have S-video output jack to connect a TV. But connecting to TV is possible via camera dock connector.
- Kodak Easyshare CX7330 a/v connector Pinout of A/V port for CX7330
- Kodak U-8 cable C1013, C180, C182, C190, C310, C315, C330, C340, C360, C433, C503, C513, C530, C533, C603, C643, C653, C663, C703 C713, C743, C763, C875, C913, CD33, CD40, M1063, M1073 IS, M1093 IS, M340, M341, M380, M381, M753, M763, M853, M863, M893 IS, P712, P880, V1003, V550, V803, Z1012 IS, Z1015 IS, Z1085 IS, Z1275, Z612, Z650, Z700, Z710, Z712 IS, Z730, Z740, Z760, Z812 IS, Z8612 IS, Z885, Z915, Z950, Z980, Z981, ZD710
- Nikon cameras MC-22 for D200, D300, D700, D3, D3x focus / shutter connector also used by the Fuij S3 and S5 Pro. Official cable is MC-22,MC-30 or MC-36.
- Nikon Coolpix UC-E1 USB + serial connector for Nikon CoolPix 4300, 4500, 5000, 5400, 5700, 8700, 800, 880, 885, 990, 995; Toshiba PDR-3300, PDR-3330, PDR-4300, PDR-M70, PDR-M71, PDR-M81. Nikon cable parts are : UC-E1 or MC-EU1 , Pentax I-USB3-E/I-USB2-C
- Nikon D70s, D80 MC-DC1 focus/shutter connector
- Nikon D90, D3100, D3200, D3300, D5000, D7000 focus / shutter MC-DC2 connector
- Nikon TTL Hot-shoe interface
- Nikon UC-E6 USB and A/V cable This cable is used in many Nikon and some other cameras.
- Digital cameras (AGFA, Olympus) to PC (COM) cable
- Olympus C-2000 Zoom, C-2020 Zoom, C-2100, C-2500L, C-3000 Zoom, C-3030 Zoom, D-220L, D-320L, D-340L/R, D-360, D-400 Zoom, D-450 Zoom, D-460 Zoom, D-490, D-500L, D-600L, D-620L, D-830L Digital Cameras serial cable scheme RS-232 to 2.5 Jack Cable. The stereo plug may be wired directly to the PC serial port
- Olympus E-PL2, E-P2, E-P1, E-620, E-30, E-400, E-510, E-520, XZ-1, SZ-20, SZ-30 MR, SP-565, SP-570, SP-590 cameras USB/Video/shutter connector and USB cable should also work with C-5500 Sport Zoom, C-7000 Zoom, D-425, D-435, D-545 Zoom, D-595 Zoom, D-630 Zoom Evolt E-330, Evolt E-500, FE-140, FE-130, FE-120, SP-310, SP-320, SP-350, SP-500Z, SP-500 UZ, SP-700 Stylus Digital 500, Stylus Digital 600, Stylus Digital 700, Stylus Digital 710, Stylus Digital 720 SW, Stylus Digital 800 Stylus 810, Stylus Verve, Stylus Verve S
- Samsung SUC-C3 usb data and charging cable for Samsung I8, i80, L100, L110, L120, L200, L201, L210, L310, L310W, L313, L313W, M100, M110, M310, M310 W, NV4, NV9, NV30, NV33, NV40, NV103, NV106, P800, P1000, P1200, SL50, SL102, SL201, SL202, SL310, SL310W, SL420, SL502, SL600, SL620, ST45, ST50, ST60, ST70, ST500, ST5000, TL9, TL90, TL100, TL105, Tl110, TL205, TL210, TL220, TL240, PL50, PL55, PL57, PL60, PL65, PL100, PL150, ES55, ES57, ES63, ES65, ES70, HZ10W, HZ15W, HZ30W, WB500, WB550, WB600, WB5000, D+
- Sony 10-pin A/V & LANC cable connector Sony A/V remote Proprietary 10 pin "D" special conector. Connection found on newer Sony consumer Video Cameras and for most Sony MiniDV & DVD Camcorders. A/V cable is Sony VMC-15FS
- Sony 14 pin for some old Sony Betamax/Betacord cameras like SONY HVC3000C
- Sony 9-pin protocol he Sony 9-Pin Protocol or P1 protocol is a two-way communications protocol to control advanced video recorders. It uses an RS-422 D-sub 9-pin connector, where bi-direction communication takes place over a four wire cable.
- Sony DCR-PC110E A/V (jack 4pin to 3 RCA) cable
- Sony DCRA-C171 docking station USB for Sony SR32, SR42, SR52, SR-62, SR72, SR82, SR200, SR300
- Sony Digital Media Port (DMPORT) The Digital Media Port (DMP or DMPort) is an interface for analog audio and video signal and digital control that Sony proposed for some of its A/V products.
- Sony DSC-W310 USB cable Compatible with Sony CyberShot DSC-H90, DSC-S650, DSC-S700, DSC-S750, DSC-S780, DSC-W180, DSC-W190, DSC-W310, DSC-W320, DSC-W330, DSC-W370, DSC-W510, DSC-W530, DSC-W550, DSC-W610, DSC-W620, DSC-W630, DSC-W650, DSC-W670, DSC-W690, DSC-W710, DSC-W730 cameras
- Sony LANC cable this cable may be used for dump/restore camcorder's firmware, unlock DV-in, change internal registers in Sony camcorders
- Sony LANC interface available at the modern SONY camcorders
- Sony RM-S1AM shutter release cable connector
- Sony wireless receiver audio input connector This is the connector inside the slot on the back of Sony professional camcorders that can be used to hold a radio receiver.
- 4 Digital cameras and camcorders interfaces OLD hardware pinouts.