What is a USB interface? what can I do?

Universal serial bus (USB) is a serial bus standard for connecting computer systems with external devices, and it is also a technical specification for input and output interfaces. Widely used in personal computers, mobile devices and other information and communication products, and extended to photographic equipment, digital television (set-top box), game consoles and other related fields.

When multimedia computers first came out, the transmission interfaces of external devices were different. For example, printers can only connect LPT, modems can only connect RS232, and mouse and keyboard can only connect PS/2. The complicated interface system, coupled with the restriction that drivers must be installed and restarted before they can be used, will bring troubles to users. Therefore, it is an inevitable trend to build a unified external transmission interface that supports easy plugging and unplugging, and USB came into being.

The latest generation of USB is USB4 with a transmission speed of 40gbit/s. Besides, only a few USB Type-A, Micro-B and new USB Type-C connectors are no longer positive and negative.

Extended data

USB was originally initiated by Intel and Microsoft, and its biggest feature is to achieve hot plug as much as possible. When the device is plugged in, the host enumerates the devices and loads the required drivers, so it is far more convenient to use than buses such as PCI and ISA.

USB is much faster than the standard bus of traditional computers, such as parallel port (such as EPP, LPT) and serial port (such as RS-232). The maximum transmission rate of USB 1. 1 (USB 2.0 at full speed) is 12Mbps, that of USB 2.0(USB 2.0 HiSpeed) is 480Mbps, and that of USB 3.0(USB 3.2 Gen 1) is 5Gbps. Usb 3.1(usb3.2gen2x1) is 10Gbps, while USB 3.2(USB 3.2 Gen2x2) is 20Gbps, and the recently released USB 4.0 has a speed of 40Gbps.

The design of USB is asymmetric, which is composed of a host controller and several devices connected to form a tree through hub devices. A controller can have at most five hubs, including the hub, and can connect at most 65,438+028 devices, because seven pairs of specific address fields are used in the design, and the seventh power of 2 is equal to 65,438+028. Generally speaking, the USB connection of 127 means that when connecting (a device), a USB connector connected to the host is deducted, and a computer can have multiple controllers at the same time. Unlike SPI-SCSI and other standards, USB hubs do not need terminators.

Peripheral devices that USB can connect include mouse, keyboard, game pad, joystick, scanner, digital camera, printer, hard disk and network. USB is the default interface for multimedia peripherals such as digital cameras. Because the connection with the computer is greatly simplified, USB has gradually replaced the parallel port as one of the mainstream connection methods of printers.

In 2004, there were more than 65438+ billion USB devices; By 2007, high-definition digital video peripheral is the only peripheral category that USB failed to get its hands on, because it needs higher transmission rate. However, with the appearance of USB3. 1 and USB4 in 20 19, high-definition digital video peripherals and external graphics cards can also be played on USB.

In the current USB standard, it is divided into the following seven versions according to the speed level and connection mode. Note that the official major version numbers of USB-IF are only USB 2.0 and USB 3.2.

Baidu encyclopedia -USB interface