Universal Serial Bus

USB stands for ‘Universal Serial Bus’ .It is the next step in creating a computer interface that really works universally. It boasts cross-platform compatibility for Macintosh, Linux/UNIX, and all versions of Windows since 98SE. The USB connector ports are available standard on virtually every computing machine manufactured in the past eight years.

Ø  USB was designed to standardize the connection of computer peripherals, such as 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

Ø  USB are now used to connect devices such as mobile phones, music players, personal digital assistances etc. to the computer.

Ø  USB has effectively replaced a variety of earlier interfaces, such as serial and parallel ports, as well as separate power chargers for portable devices.

Ø  USB mass storage devices are now widely used for data transmission.

Ø  USB devices are used to interface electronic devices with computer.

Many versions of USB has been released, such as USB 1.0, USB 2.0, USB 3.0 , based on the transfer rate. USB 3.0 has the highest transfer rate (625 MB/s), about 10 times more faster than USB 2.0 (60 MB/s)

USB standard connectors are of two types, USB standard A & USB standard B, based on their shape.

The structure of  USB 1.x and 2.0. are shown. The pin 1 provides +5 V, pin 2 (data-) & pin 3 (data+) are data pins, pin 4 is ground. A unit load is defined as 100 mA in USB 2.0, and 150 mA in USB 3.0.