Universal Serial Bus – USB
The short term USB stands for Universal Serial Bus and a serial communication that was developed by a merger of some companies – NEC and Microsoft for instance – to connect peripheral devices with a PC. A computer with a USB port, but also USB sticks can be connected at any time during system operation. In this process called Hot Swapping the external device and its features are automatically recognized.
From USB 1.0 to USB 3.1 SuperSpeed – The development of the interface
1996 was the year the first specification USB 1.0 with a data rate of 12 Mbit/s was released. With the introduction of USB 2.0 in 2000 even hard disks and video devices could be connected – thanks to the data rate of 480 Mbit/s.
Ten years ago the specifications of USB 3.0 SuperSpeed – also called USB 3.1 Gen 1 – with a data rate of 5 Gbit/s were presented. At the same time new cables and connectors were introduced. 2013 USB 3.1 – called USB 3.1 Gen 2 – was finalized and doubled up the speed of the predecessor to 10 Gbit/s. The latest specification USB 3.2 was released in 2017 and comes with a data rate of up to 20 Gbit/s.
By the way: ll spo-comm Mini-PCs are equipped with at least one USB 3.0 port!
USB transmission technologies
Using a host controller which is regularly based on the mainboard, the communication of USB can be managed. Only this host can read a devices’ information or send data to the device. The device can only send information if the host sends a query.
There are four established standards, which the USB controller chips hold on to and which are different in their performance and the implementation of features:
- Universal Host Controller Interface (UHCI): Specified in 1995 by Intel with a data rate from 1,5 to 12 Mbit/s.
- Open Host Controller Interface (OHCI): Developed by a consortium of companies and just marginal faster than UHCI.
- Enhanced Host Controller Interface (EHCI): Provides USB 2.0 features and is designed for Hi-Speed mode (480 Mbit/s). For transfer to a USB 1.0/1.1 device OHCI and UHCI has to be supported.
- Extensible Host Controller Interface (xHCI) : xHCI was released by Intel, provides USB 3.1 features and supports the SuperSpeed mode with 4 Gbit/s – with USB 3.1 even 9,7 Gbit/s.
The different plug types of USB
The Universal Serial Bus knows various plugs and connectors that differ in their measurements, but also in the possible data transmission speed.
The latest one is the universal USB Type C port, which is installed in many smartphones because of its low height and width. With this port data rates of up to 10 Gbit/s are possible, because USB 3.1 Gen 2 is supported. The USBC interface is suitable for transferring audio and video data parallel to USB data and supports DisplayPort, PCIe and Thunderbolt.