Universal serial bus is not only a serial port bus standard, but also an input-output interface specification. Widely used in personal computers, mobile devices and other related fields, and expanded to photography equipment, digital television, console and other related fields. The latest generation is USB 3. 1, is 10 Gbit/s, the tertiary voltage is 5V≤12V/20V, the maximum power supply is 100w, the new TypeC plug-in is no longer positive or negative.

The working principle of

USB is an external bus standard that controls the connection and communication between computers and external devices. USB interface with hot plug function. USB interface can be connected to a variety of peripherals, such as mouse and keyboard. USB was introduced by Intel and others in late 1994 in 1996 and successfully replaced serial and parallel ports. It has become an essential interface between computers and a host of smart devices. The USB version has evolved over the years and is now in version 3. 0. For most engineers, USB 2 is a major hurdle. The 0 interface product is: USB 2 for complexity. 0 protocol, write their own USB device driver, familiar with single-chip programming. This not only requires a lot of VC programming experience, but also need to write USB interface hardware program.

The development history

USB1.0

USB1.0 was introduced in 1996 with a speed of only 1.5Mb/s(bits per second); In 1998, the speed of the upgrade to USB1.1 was significantly increased to 12 MB/s, which can still be seen on some older devices. For this standard interface. B/s usually represents the bit transfer rate, and BPS represents the bit transfer rate, which is numerically equivalent. 1 MB /s=8 MBPS, 12 MBPS =1.5 MB /s, most mp3s are of this type.

usb 2.0

The USB2.0 specification is an evolution of the USB1.1 specification. Its transmission rate reached 480Mbps, which translates to 60MB/s, enough to meet the rate requirements of most peripherals. The "enhanced host controller interface" in USB2.0 defines a usb1.1-compliant architecture. It can drive USB1.1 devices with USB2.0 drivers. In other words, all devices that support USB1.1 can be used directly on the USB2.0 interface without worrying about compatibility issues, and accessories like USB cables, plugs, and so on can be used directly.

The change that USB interface brings to the printer application is the great increase in speed. The USB interface provides a connection speed of 12 Mbps, more than 10 times faster than the parallel port, which greatly reduces the time to print files at this speed. The USB2.0 standard further increases the interface speed to 480 Mbps, 20 times faster than regular USB, greatly reducing the transfer time of printed files.

USB 3.0

USB 3.0 PromoterGroup, a group of industry giants including Intel, Microsoft, HP, Texas instruments, NEC and st-nxp, announced the new USB 3. The standards formulated by the organization have been officially completed and published. The theoretical velocity of USB3. 0 is 5. At 0Gb/s, it can only reach 50% of the theoretical value, nearly 10 times that of USB2. 0. The physical layer of USB3. 0 adopts 8B/10B encoding mode, and the theoretical calculation speed is 4Gb/s, while the actual speed must deduct the protocol overhead and reduce on the basis of 4Gb/s. Can be widely used in PC peripherals and consumer electronics.

USB3.0 will be called "USBSuperspeed "in real device usage, consistent with previous USB1.1Fullspeed and USB2.0Highspeed. Commercial controllers supporting the new specifications are expected to be available in the second half of 2009, while consumer-grade products are already on the market.

USB3.1

USB3.1Gen2 is the latest USB specification, sponsored by Intel and others. Data transfer speeds can be increased to 10 Gbps. Compared to USB3.0, the new USB technology USES a more efficient data encoding system, providing more than twice the effective data throughput. It is fully backwards compatible with existing USB connectors and cables.

USB3.1Gen2 is compatible with existing USB3.0(i.e. USB3.1Gen1) software stack and device protocols, 5 Gbps hubs and devices, and USB2.0 products.

Usb-if's latest USB naming specification, the original USB3.0 and USB3.1 will no longer be named, and all USB standards will be called USB3.2. For compatibility, USB3.0 to USB3.2 will be called USB3.2Gen1, USB3.2Gen2, USB3.2Gen2X2, respectively.

The main advantages of editing

USB devices have the following main advantages:

1. It can be hot-plugged. That is to say, when using external devices, users do not need to shut down and start up and other actions, but in the computer work, directly insert the use of USB.

2.Two of them. It's easy to carry. Most USB devices are "small, light and thin." For users, it is convenient to carry a large amount of data.. Of course, a USB hard drive is preferred.

3. Unified standards. We are universal ide interface hard disk, serial mouse keyboard, parallel printer scanner, but with USB, these application peripherals can use the same standard and PC connection, then USB hard disk, USB mouse, USB printer, etc.

4. You can connect multiple devices. USB usually has multiple ports on a PC and can be connected to multiple devices at the same time, if connected to a four-port USBHUB, you can connect to four USB devices, etc., you can connect devices to one PC at the same time without any problems (note: up to 127 devices).

Interface category editing

With the popularity of various digital devices, especially MP3 and digital cameras, the number of USB devices around us is gradually increasing. However, although these devices use USB ports, the data cables for these devices are not exactly the same. These data lines are the same at the end of the PC connection, but when connected to the device, a variety of different interfaces are usually used due to size. The following is a brief introduction to the various applications of the Mini subinterface.

B - 5 Pin

This kind of interface can be said to be the most common interface, because it has excellent anti-plug performance and small size, so it has won the favor of more and more manufacturers. Today, the interface is widely used in today's card readers, MP3 players, digital cameras and mobile hard drives.

B - 4 pin

This interface is common in digital products of the following brands: Olympus C and E series, kodak most digital camera, samsung MP3 products (such as Yepp), SONY DSC series, compaq iPAQ series.

MiniB 4Pin has another form, MiniB 4PinFlat. As the name implies, this interface is much flatter than MiniB 4Pin and is widely used in devices.

B - 8 pin

The interface, compared with the previous normal type, is to change the original d-connector into a round connector and to prevent the wrong convex shape from being inserted in the side.

This connector can be found in some nikon digital cameras, but the Coolpix series is more common. While Nikon has stuck with this interface, newer models, such as the D 100 and CP 2000, also use the most popular Mini B5 Pin interface.

B - 8 pin - 2 x 4

This interface is also a relatively common interface, such as Iriver's famous MP3 series, which is called "iron triangle "180TC. This interface is also a wide range of applications, but the miniB 5-pin interface has been completely replaced by the 3xx series Iriver.

Micro USB

Micro USB is a portable version of USB 2. Standard, smaller than the mini USB port used in some mobile phones. Micro USB is the next generation mini USB specification. USB implementer BBS (USB - IF) was organized by USB standardization on January 4, 2007. The micro USB OTG support, mini USB, and 5 pin. The definition of micro series including micro B series standard equipment, OTG devices micro AB groove, micro series is unique in their contains a stainless steel casing, easy to insert.

Framework standard "is" universal mobile terminals and other mail tunnels technology and equipment of the power adapter and charger package ", on October 26, 2009 in Geneva Switzerland itu -t and adopted at the plenary meeting of the fifth team discussion, and apply for enter the approval process, this actually means that the phone charger will standardize all over the world.

Type-C

If USB is released in August 2014, it is the USB standardization organization that aims to solve the long-term physical interface specification inconsistency of USB interface. The biggest characteristic of the c-type interface is to support the insertion of positive and negative directions, which officially solves the world problem of "USB will never be blocked ".

The characteristics of c-type hardware interface are obvious, mainly including the following points:

(1) support positive and negative insertion to solve problems that cannot be inserted in practical applications;

(2) thin interface, which can support thinner devices, making the design of portable devices thinner and smaller;

(3) support more power transmission, up to 100 watts, support more high-power load equipment.

(4) support single port and double port -c type, flexible application.

(5) support two-way power transmission, transformation and reception.