USB-Wiki-Image.pngWhat is USB?

USB stands for Universal Serial Bus. It exists as a standard for connectivity of peripherals to a computer. It is a type of serial port, which means bits travel one at a time, though, in this case at very high rates.


Speed

Over its history, USB has had speeds ranging from 1.5 Mbit/s to 480 Mbit/s. 1.5 Megabits per second being unbearably slow, USB had to adapt to increasing speed and power in computation.

How it works
USB has a range of uses, which will be mentioned below. Its mode of function, however, is universal to all devices with the interface, hence the "U" of USB. It works to allow data transfer from the computers motherboard to various external devices. A useful example would be that of how a keyboard uses USB as opposed to how a flash drive uses USB.

  • A keyboard uses the USB interface to send information in the form ASCII encoded letters, numbers, and symbols to the motherboard (namely the CPU) for use in word processing programs, or any other software that requires textual input. There are two parts of this process that are important to note: primarily the fact that keyboard does not need to be plugged into the wall for a power source, even though it needs electricity for its circuits to function. USB allows connected devices to draw a small amount of electricity directly from the computers built in power-source. USB differs in this way from other types of connection such as FireWire which still require the connected device to be plugged in with its own power source. The second note to be made about USB in this function is that because it is a serial bus (the "SB") it can only transmit data from the keyboard to the computer one bit at a time. This is why if you press two keys on the keyboard, even at the exact same moment, only one character would appear on screen. The keyboard can only send one character at a time, where as a parallel bus can send multiple bits at time to be reassembled at the destination. Some would think that a serial bus is therefor less efficient, when in fact it would be more difficult to connect a keyboard over a parallel bus because if you were to press two keys at the same time, the computer would have to decide for itself which character should go first, and you could end up with a jumbled mess of corrupt data.

  • A flash drive (or thumb drive) uses the same principals in a slightly different way. Flash drives are given their name because of the kind of memory they hold data on: flash memory. Flash memory resembles the RAM on your computer, where there are no moving parts (unlike the hard drive) and where the memory only exists so long as there is an electric charge moving through the RAM chip. Flash memory differs from RAM in that it is maintained on the medium even when no electric charge is present, though electricity must be applied to see it and change it which is where USB comes in. The flash drive uses electricity from the computer (it would be horribly inconvenient to need to plug in your flash drive, wouldn't it?) to activate the medium and allows the data saved there to be accessed and altered. This is the other way in which flash drives use USB differently than a keyboard; while it is meaningless for the computer to send information back to the keyboard, it is necessary for the computer to be able to send information to the flash drive. In this relationship, the flash drive has two distinct connections to the comuter; one for data out and the other for data in.


History

  • USB to USB 2.0
    • The original incarnation of USB, released in 1996, was not particularly efficient, and it had not yet been set as the standard for connectivity. Its maximum speed of data transfer was a lowly 12 Mbit/s and the physical connection between the computer and the peripheral was prone to damage.
    • USB 2.0 was introduced to the market in April of 2000. It sported considerably faster rates of data transfer (480 Mbit/s), a more durable point of connection, and due to its adoption by Apple for its original iMac it quickly became an industry standard.



Future

  • USB 3.0
    • 3.0 was introduced by Pat Gelsinger on Septermber 18, 2007. The software has been released to developers and boasts an impressive 5 Gb/second transfer rate! To achieve these impressive speeds, they called on SuperSpeed bus. SuperSpeed bus uses a dual-bus architecture to enable transfer at 3.0, as well as USB 2.0 ports, simultaneously. USB 3.0 uses 150mA of power per unit load, a 50% increase on USB 2.0. USB 3.0 can be wired from 1 unit load up to 6, which allows for up to 900mA of bus power, 80% more than USB 2.0.
    • Applications - USB 3.0 should be available for manufacturing components as early as the Summer of 2009. Consumer components of 3.0 are not expected to be released publicly until 2010.

Consumer Products


Cameras - Camera connections started with Serial connections, but due to the slow transfer times, USB was introduced to digital photography. The original USB connections used USB 1.1, which was capable of transferring at 11 megaBITs/second. As advances were made, upgrades to the USB connections were introduced. Camera makers began using USB 2.0. which could also plug into USB 1.1 ports. To enable the proper amount of transfer speed, it must be connected to a female USB 2.0 port, but can deliver up to 480 megaBITs/second.


Printers - The Universal Serial Bus (USB) is a communications architecture that gives a PC the ability to interconnect a variety of devices via a simple four-wire cable. One such device is the printer. Traditionally, printers have been interfaced using the following technologies:

      1. Unidirectional parallel port
      2. Bi-directional parallel port
      3. Serial port
      4. SCSI port
      5. Ethernet/LAN
        There are other, more sophisticated printer interfaces, but the ones previously listed are the most popular. USB offers a much greater throughput capability than the serial port and is comparable in speed to the parallel port. This makes both parallel and serial printers good candidates for interfacing with USB.

Scanners
- Like cameras and printers, the original scanners connected via the serial port. This caused slow transmission and poor picture
800px-USB_Stick-Schlaufe-0-Verlust.JPG
Flash Drive
quality. Currently most scanners use USB 1.1 to broadcast their image to the host computer; however, USB 2.0 is available and will allow you to get faster, higher-quality images than USB 1.1.

Flash Drives - Flash drives are memory storage devices that were created to implement quick uploading and transferring from one comuter to another. Flash drives are commonly used for storing and sharing pictures, music, files, and information.

Memory Card Readers - Memory Card Readers allow the user to transfer a flash memory card's contents to a computer's hard drive. Flash memory cards are most commonly used in consumer products such as phones, cameras and MP3 players. Often times, transferring data straight from the memory card using the reader yeilds much higher speeds than just plugging the device directly into the computer.

Input Devices - There are numerous types of input devices that use USB to communicate with a computer. Keyboards that offer many different button arrangements such as media controls and even their own display screen are very popular. Mice some with similar configurations of special buttons. USB microphones allow a user without a standard microphone jack to use technologies like voice over ip.
Other Devices that use USB

IPod_Classic_6th_Generation.jpg
iPod Classic
Portable MP3 Players - The MP3 player market has exploded in the last five or so years. Part of which has facilitated this boom was the ease of connectibility of USB connection. These players use either flash memory or hard drives to store music files on the player. USB allows for a simple, fast connection to the consumer's computer for copying music files to the device. Many manufacturers do not even include a wall charger, relying on charging your player strictly over USB. This list includes the world's most popular MP3 player manufacturer, Apple.

Game Consoles
- Given the overall use and ability of USB ports, it was only a matter of time before game consoles started including them. The first system to have USB portswas the Playstation 2, using it for only a few things, but the possibilities were limitless. Most commonly, the USB ports were used for a keyboard and mouse, especially for players wishing to play Final Fantasy XI, the first game of the Final Fantasy series to have online capabilities. Some games, such as Gran Tourismo 4, also allowed you to plug in a thumb drive to save pictures, or a USB printer to print and share them with friends. The software that determined which USB devices was extremely limited and depended entirely on the game being played, however. The next generations of systems all include USB ports for a variety of uses, from guitar-shaped controllers, to keyboards, to anything that could be used for fun and profit.


Vehicles - The USB port has even gone so far as to make it into automobiles. Until last year, Volkswagon has been the only company to have implemented USB drives in their cars. The first of which were the Golf and Toureg models, and in the future, the Visteon Corporation intends on including USB ports on future vehicles a full 18-20 months earlier (http://www.everythingusb.com/ visteon.html). Other companies have begun the production of cars with USB ports as well, such as the DB568RUSB, presented at the Paris Motor Show 2008 (http://uk.cars.yahoo.com/ 19122006/49/usb-equipped-car- stereo-14.html).

Tablet PCs - With the advent of touchscreen technology, keyboards became superfluous to some, and the way became paved for the Tablet PC. These Tablet PCs have all the capabilities of their Laptop predecessors, but often boast a smaller size, and as a result, carry a heftier price tag. Many of them have reversible screens, and for those which don't, the screens can detach entirely. The first commercially available Tablet PC was the GRiDPad in September of 1989, and it used a Touchscreen for the input. Nowadays, on Tablets without keyboards, USB Ports are available to attach one.



Citations

http://www.everythingusb.com/ visteon.html

http://uk.cars.yahoo.com/ 19122006/49/usb-equipped-car- stereo-14.html

http://en.wikipedia.org/wiki/Usb

http://en.wikipedia.org/wiki/Tablet_PC
http://en.wikipedia.org/wiki/Playstation_2
http://en.wikipedia.org/wiki/USB_flash_drive__