USB
Universal Serial Bus (USB) is an industry standard that specifies the physical interfaces and protocols for connecting, data transferring and powering of hosts, such as personal computers, peripherals, e.g. keyboards and mobile devices, and intermediate hubs.[2] USB was designed to standardize the connection of peripherals to computers, replacing various interfaces such as serial ports, parallel ports, game ports, and ADB ports.[3] It has become commonplace on a wide range of devices, such as keyboards, mice, cameras, printers, scanners, flash drives, smartphones, game consoles, and power banks.[4]
As of 2023[update], USB consists of four generations of specifications: USB 1.‘‘x’’, USB 2.0, USB 3.‘‘x’’, and USB4. Since USB4 the specification enhances the data transfer and power supply functionality with
connection-oriented, tunneling architecture designed to combine multiple protocols onto a single physical interface, so that the total speed and performance of the USB4 Fabric can be dynamically shared.
USB4 particularly supports the tunneling of the Thunderbolt 3 protocols, namely PCIe (load/store interface) and DisplayPort. USB4 also adds host-to-host interfaces.[5]
Each specification subversion supports different maximum data transfer speeds from 1.5 Mbit/s in USB 1.0 to 80 Gbit/s in USB4.[6][7][5] USB also provides power supply to peripheral devices; the latest versions of the standard extend the power delivery limits for battery charging and devices requiring up to 240 watts (USB Power Delivery (USB-PD)).[8] Over the years USB(-PD) has been adopted as the standard power supply and charging format for many mobile devices, such as mobile phones, reducing the need for proprietary chargers.[9]
USB connector interfaces are classified into three types: A (host), B (peripheral), and C (2014, replaces A and B). The A and B types know different sizes: Standard, Mini, and Micro. The standard size is the largest and is mainly used for desktop and larger peripheral equipment. The mini size was introduced for mobile devices, but it was replaced by the thinner micro size. The micro size is nowadays the most common for smartphones and tablets. The USB Type-C connector interface is the newest and the only one applicable to USB4. It is reversible and can support various functionalities and protocols; some are mandatory, many just optional, and depending on the type of the device: host, peripheral device, or hub.[10][11]
