USB Universal Serial Bus Tutorial

USB, Universal Serial Bus has versions including USB 1.1, USB 2, & USB3 / 3.1 and provides convenient and effective connectivity for computer related systems.

USB Universal Serial Bus Includes:
USB introduction     USB standards     Connectors, pinouts & cables     Data transfer & protocol     USB 3     USB-C    

USB, Universal Serial Bus is one of the most common interfaces for connecting a variety of peripherals to computers and providing relatively local and small levels of data transfer.

USB interfaces are found on everything from personal computers and laptops, to peripheral devices, mobile phones, cameras, flash memory sticks, back up hard-drives and very many other devices.

The Universal Serial Bus, USB provides a very simple and effective means of providing connectivity, and as a result it is very widely used.

Whilst USB provides a sufficiently fast serial data transfer mechanism for data communications, it is also possible to obtain power through the connector making it possible to power small devices via the connector and this makes it even more convenient to use, especially ‘on-the-go.’

USB Type A connector on a cable

USB evolution

The USB interface was developed as a result of the need for a communications interface that was convenient to use and one that would support the higher data rates being required within the computer and peripherals industries.

The first proper release of a USB specification was Version 0.7 of the specification. This occurred in November 1994. This was followed in January 1996 by USB 1.0. USB 1.0 was widely adopted and became the standard on many PCs as well as many printers using the standard. In addition to this a variety of other peripherals adopted the USB interface, with small memory sticks starting to appear as a convenient way for transferring or temporarily storing data.

Summary of USB Versions and Performance
USB Version Details
USB 1 Low speed:   1.5 Mbps
Full speed:   12 Mbps
USB 2 'High Speed' rate of 480 Mbps
USB 3 Raw data transfer rates of 4.8 Gbit/s
Type B USB connector

With USB 1.0 well established, faster data transfer rates were required, and accordingly a new specification, USB 2 was released. With the importance of USB already established it did not take long for the new standard to be adopted.

With USB defining its place in the market, other developments of the standard were investigated. With the need for mobility in many areas of the electronics industry taking off, the next obvious move for USB was to adopt a wireless interface. In doing this wireless USB would need to retain the same flexible approach that provided the success for the wired interface. In addition to this the wireless USB interface needs to be able to transfer data at rates which will be higher than those currently attainable with the wired USB 2 connections. To achieve this ultra-wideband UWB technology is used.

USB capabilities

The basic concept of USB was for an interface that would be able to connect a variety of computer peripheral devices, such as keyboards and mice, to PCs. However, since its introduction, the applications for USB have widened and it has been used for many other purposes including, including measurement and automation.

In terms of performance, USB 1.1 enabled a maximum throughput of 12 Mbps, but with the introduction of USB 2.0 the maximum speed is 480 Mbps.

In operation, the USB host automatically detects when a new device has been added. It then requests identification from the device and appropriately configures the drivers. The bus topology allows up to 127 devices to run concurrently on one port. Conversely, the classic serial port supports a single device on each port. By adding hubs, more ports can be added to a USB host, creating connections for more peripherals.

USB advantages & disadvantages

USB has many advantages when compared to other technologies, but it also has a number of disadvantages which need to be considered when deciding on a technology to be used.

Advantages & Disadvantages of USB
  • Ease of use
  • Acceptable data rate for many applications
  • Robust connector system
  • Variety of connector types / sizes available
  • Low cost
  • Data transfer not as fast as some other systems
  • Limited capability & overall performance

USB has many advantages and this is why it is so widely used. However, its simplicity and ease of use, mean that it is not always applicable in applications where more sophisticated interfaces are required for very high speed data transfer.

USB, Universal Serial Bus is used virtually without exception on most PCs, even Macbooks which have migrated to the lightning connector have interface cables to enable them to easily interface with USB. With the host of other peripherals that use USB, connectivity using this interface is essential for virtually every computer based device.

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