Good to know: What is USB?

27.09.2018

After kicking off the interface series two weeks ago with the “What is LAN?” article, we continue today with the next in the series. The USB port is part of everyday life for all of us: whether it’s a wired or wireless mouse, charging a smartphone or simply connecting a USB stick to the computer. What exactly is behind the ubiquitous USB? What are the differences between the various specifications such as USB 2.0 and USB 3.0 Gen 2? We’ll tell you!

Universal Serial Bus - USB

The well-known abbreviation USB stands for Universal Serial Bus and describes a serial bus system that was developed by a merger of several companies - including NEC and Microsoft - for connecting peripheral devices to PCs. A computer with a USB port, but also USB sticks, can be connected to each other during operation, whereby the external device and its properties are automatically recognized. This process is known as hot plugging.

From USB 1.0 to USB 3.1 SuperSpeed - the development of the interface

The first USB 1.0 specification with a data rate of 12 Mbit/s was launched on the market in 1996. With the introduction of USB 2.0 in 2000, hard disks and video devices could now also be connected thanks to a data rate of up to 480 Mbps.

Ten years ago, the new specifications for USB 3.0 SuperSpeed - also known as USB 3.1 Gen. 1 - with a data rate of 5 Gbit/s were introduced. New cables, plugs and sockets were also introduced at the same time. In 2013, USB 3.1 - known as USB 3.1 Gen. 2 - which doubled the speed of its predecessor to 10 Gbit/s, was completed. The very latest USB 3.2 specification with a data rate of up to 20 Gbit/s was only published in 2017.

By the way: Every spo-comm Mini-PC system is equipped with at least one USB 3.0 port!

USB transmission technologies

USB communication is controlled by a host controller, which is usually installed on the mainboard. Only this controller can read the data of a device or send data to the device. However, the device may only send data if this is requested by the host controller.

There are four established standards to which the USB controller chips adhere and which differ in terms of their performance and the implementation of functions:

Universal Host Controller Interface(UHCI): Was specified by Intel in 1995 and offers data rates of 1.5 to 12Mbit/s.

Open Host Controller Interface(OHCI): Developed by a consortium of companies and only marginally faster than its counterpart UHCI.

Enhanced Host Controller Interface(EHCI): Provides USB 2.0 functions and is designed for Hi-Speed mode (480 Mbit/s). When transferring to a USB 1.0/1.1 device, OHCI & UHCI must still be supported.

Extensible Host Controller Interface(xHCI): xHCI was published by Intel in 2010, offers USB 3.0 functions and provides the SuperSpeed mode with 4.0 Gbit/s - with USB 3.1 even 9.7 Gbit/s.

The different connector types of a USB

The Universal Serial Bus has various plugs and sockets that differ in terms of their dimensions, but also in terms of the possible data transfer speeds.

The latest of these is the universal USB type C connection, which is also used in smartphones, among other things, due to its low height and width. Data rates of up to 10 Gbit/s or 1.25 Gb/s are possible here, as USB 3.1 Gen 2 is supported. The USBC interface is suitable for transferring audio and video data in parallel with USB data and also supports DisplayPort, PCIe & Thunderbolt.

Discover all spo-comm Mini-PCs!

To the "What is LAN?" article