What is USB? - Plastic Surgery and Aesthetics Network

What is USB?

Introduction to USB

USB is the abbreviation of English universal serial bus, which means "universal serial bus" in Chinese. It is not a new bus standard, but an interface technology applied in PC field. USB was put forward by Intel, Compaq, IBM and Microsoft at the end of 1994. But it was not widely used until recently. Since June1994+065438+1October 1 1 released the USB version V 0.7, the USB version has developed for many years, and now it has developed to version 2.0, which has become a standard expansion interface in computers. At present, the mainboard mainly uses USB 1. 1 and USB2.0, and the USB versions are very compatible. USB uses a 4-pin plug as a standard plug, which can connect all peripherals in daisy chain, and can connect up to 127 external devices without losing bandwidth. USB needs the support of host hardware, operating system and peripherals to work. At present, the motherboard generally adopts a control chipset supporting USB function, and a USB interface socket is also installed on the motherboard. In addition to the socket on the backplane, a USB pin is reserved on the motherboard, which can be connected to the front of the chassis as a front USB interface for easy use (note that when wiring, you should read the motherboard manual carefully and connect it according to the diagram, and don't damage the equipment because of wrong connection). Moreover, USB interfaces can also be interconnected through special USB cables, and more interfaces can be extended through Hub. USB has the advantages of high transmission speed (USB 1. 1 is 12Mbps, USB2.0 is 480Mbps, and USB3.0 is 5 Gbps), easy to use, hot plug support, flexible connection and independent power supply. , you can connect a mouse, keyboard, printer, scanner, camera, flash drive, MP3 player, mobile phone and digital equipment.

USB is an external bus standard, which is used to standardize the connection and communication between computers and external devices. USB interface supports plug-and-play and hot-plug functions of devices.

USB interface can connect up to 127 kinds of peripherals, such as mouse, modem, keyboard, etc. Since the advent of 1996, USB has successfully replaced serial port and parallel port and become one of the necessary interfaces for personal computers and a large number of intelligent devices.

USB version

First generation: USB1.0/1.1The maximum transmission rate is 12Mbps. Introduced in 1996.

Second generation: the maximum transmission rate of USB 2.0 is as high as 480Mbps. Usb1.0/1.1and USB 2.0 interfaces are compatible with each other.

Third generation: USB 3.0 has a maximum transmission rate of 5Gbps and is backward compatible with USB1.0/1.1/2.0.

Application of usb:

With the rapid development of computer hardware, peripheral devices are increasing day by day. Keyboards, mice, modems, printers and scanners have long been known, and digital cameras and MP3 walkmen have followed. With so many devices, how to access personal computers? USB was born for this purpose. USB is an interface that standardizes and simplifies the connection of computer peripherals, and its specifications are formulated by Intel, NEC, Compaq, DEC, IBM, Microsoft and Nortel.

The transmission rate of USB 1. 1 standard interface is 12Mbps, but a USB device can only get 6Mbps transmission bandwidth at most. So you have to connect an external optical drive, at most a six-speed optical drive, and it can't be higher. However, if you want to play MPEG- 1 VCD movies immediately, you need at least 1.5Mbps transmission bandwidth, which USB can do, but it may be very difficult for USB to play MPEG-2 DVD movies with four times the data. If you add AC-3 audio data, it will be difficult for USB devices to play them immediately.

Theoretically, a USB interface can support 127 devices, but at present it can't reach this number. In fact, for a computer, the number of connected peripherals rarely exceeds 10, so this number is enough for us to use.

Another significant advantage of USB is that it supports hot plug, which means that you can safely connect or disconnect USB devices when you turn them on, thus realizing real plug and play.

However, not all Windows systems support USB. There are many different versions of Windows system at present. Among these versions, only the system above Windows98 has good support for USB, and other Windows versions can't fully support USB. For example, the retail version of Windows95 does not support USB, and only the later version of Windows95 bundled with PC supports USB.

Although USB devices have been widely used at present, USB 1. 1 interface is more common, and its transmission speed is only 12Mbps. For example, it takes four seconds for you to scan a 40M-sized picture with a USB 1. 1 scanner. This speed makes users feel very inconvenient. If there are several pictures to scan, they have to wait patiently.

The demand of users is the driving force to promote the development of science and technology, and manufacturers have also recognized this bottleneck. At this time, Compaq, Hewlett-Packard, Intel, Lucent, Microsoft, NEC and Philips jointly formulated the USB 2.0 interface standard. USB 2.0 improves the data transmission speed between devices to 480Mbps, which is about 40 times faster than USB 1. 1 standard. The biggest advantage of speeding up is that users can use more efficient external devices, and peripherals of various speeds can be connected to USB 2.0 lines without worrying about the bottleneck effect in data transmission.

So, if you use a USB 2.0 scanner, it's completely different. It only takes about half a second to scan a 40-meter picture, and it passes in a blink of an eye, which greatly improves the efficiency.

Moreover, USB2.0 can use cables with the same specifications in the original USB definition, and the connector specifications are exactly the same, which maintains the excellent characteristics of USB 1. 1 on the premise of high speed, and USB 2.0 devices will not conflict with USB 1. X devices are used together.

USB2.0 is compatible with USB 1. 1, that is to say, USB 1. 1 devices can be used in common with USB2.0 devices, but at this time, USB2.0 devices can only work at full speed (12Mbit/s). USB2.0 has three working speeds: high speed 480Mbit/s, full speed 12Mbit/s and low speed 1.5 mbit/s, in which full speed and low speed are designed to be compatible with USB 1. 1 and USB 1.0. Therefore, when purchasing USB products, don't just listen to merchants promoting USB2.0, but also find out whether it is a high-speed, full-speed or low-speed device. The USB bus is a one-way bus, and the main controller is on the PC, so USB devices can't actively communicate with the PC. In order to solve the problem of communication between USB devices, related manufacturers have developed USB OTG standard, which allows embedded systems to communicate with each other through USB interface, thus getting rid of PC.

The new version of USB2.0 specification was renamed as USB standard, and the original USB 1. 1 was changed to USB 2.0 full speed (full speed version), and the original USB 2.0 was changed to USB 2.0 high speed version. At the same time, a new logo was released. It goes without saying that the high-speed USB 2.0 is definitely faster than the full-speed USB 2.0.

USB and IEEE 1394 1. What are the similarities between USB and IEEE 1394?

Both are universal external device interfaces.

Both can transmit large amounts of data quickly.

Both can be connected to many different devices.

Both support hot dialing.

Both can be used without an external power supply.

2. What's the difference between 2.USB and IEEE 1394?

Their transmission rates are different. Compared with IEEE 1394, the transmission rate of USB is really nine Niu Yi hairs. At present, the transmission rate of USB is only 480Mbps, which can only connect low-speed devices such as keyboards, mice and microphones, while IEEE 1394 can use 3.2Gbps, which can be used to connect digital cameras, scanners, information appliances and other devices that need high speed.

The structure of the two is different. When USB is connected, there must be at least one computer and a HUB for interconnection. The whole network can have at most 127 devices. IEEE 1394 does not need a computer to control all devices, nor does it need a hub. IEEE 1394 can connect multiple IEEE 1394 networks with bridges, which means that after 63 IEEE 1394 devices are implemented with IEEE 1394, other IEEE 1394 networks can also be connected with bridges.

They are different in intelligence. IEEE 1394 network can automatically reset the network when adding or deleting devices. USB uses HUB to judge the increase or decrease of connected devices.

The application degree of the two is different. Now USB has been widely used in all aspects, almost every PC motherboard has a USB interface, and USB2.0 will further expand the application scope of USB. IEEE 1394 is only applied to multimedia aspects such as audio and video.

[Edit this paragraph] Front USB interface

The front USB interface is a USB expansion interface located on the front panel of the chassis. At present, there are more and more external devices using USB interface, such as mobile hard disks, flash drives, digital cameras and so on. But every time you use these devices (especially frequently used mobile storage devices), you have to drill into the back of the chassis and use the USB interface on the motherboard, which is obviously inconvenient. The front USB interface provides users with good usability in this respect. At present, the front USB interface has almost become the standard configuration of the chassis, and the chassis without the front USB interface is very rare.

The front USB interface can only be used if it is connected to the corresponding front USB pins on the motherboard (generally 8-pin, 9-pin or 10 pin, two USB are paired, and each USB uses 4 pins for signal transmission and power supply). When connecting the front USB interface, be sure to read the relevant contents in the motherboard manual and chassis manual carefully in advance, and never connect incorrectly, otherwise it will damage the USB device or motherboard.

In addition, because the output voltage of USB2.0 interface is 5V, the output current is 500mA. When using the front USB interface, we should pay attention to the problem of insufficient power supply of the front USB interface. When using a high-power USB device, use an external power supply or directly use the onboard USB interface of the motherboard on the back of the chassis to prevent the USB device from working normally or being damaged.

[Edit this paragraph ]USB hard disk box

At present, the mainstream, its biggest advantage is easy to use, supporting hot plug and plug and play. There are two USB standards: one is USB 1. 1 interface, with a transmission speed of only 12Mbps, and the other is USB2.0 interface with a transmission speed of up to 480Mbps. At present, USB on the motherboard supports USB 1. 1, but USB2.0 can only be supported by newer motherboards. When shopping, choose products according to personal circumstances. Although USB2.0 is backward compatible with USB 1. 1, the mobile hard disk box supporting USB 2.0 interface is more expensive than USB 1. 1.

[Edit this paragraph] Wireless USB

Jeff Ravencraft, chairman of the USB Developer Forum and technical strategy officer of Intel Corporation, said that wireless USB technology will help users get rid of complicated cable connections when connecting printers, digital cameras, music players and external disk drives with personal computers. The data transmission rate of wireless USB standard is the same as that of wired USB 2.0 standard, which is 480M per second. The difference between the two is that wireless USB requires wireless transceiver devices in personal computers or peripherals, rather than cable connections.

On the eve of the Intel Developer Forum, Ravencraft said that external disk drives, digital cameras and printers will be the first to adopt this standard. More and more products will be put on the market in the third quarter of this year.

In order to make the wireless USB standard practical, some shortcomings of this technology must be improved. On Monday, the USB standard organization published the wireless alliance specification, ensuring that computers and peripherals can only be connected through wireless USB after they have passed the certification.

Ravencraft added that USB standard has been widely used to connect digital cameras, scanners, mobile phones, PDA, DVD burners and other devices with personal computers. The wireless alliance specification specifies in detail how personal computers and peripherals can be connected through wireless USB, and a computer can connect at most 127 peripherals at the same time.

The wireless alliance specification stipulates two ways to establish a connection. The first method is to connect the computer and peripherals with cables, and then establish a wireless connection for later use. The second method is that the peripheral device can provide a series of numbers, which the user can input into the computer when establishing the connection.

Wireless USB uses ultra-wideband technology to communicate. At present, the 802. 1 1g protocol of WLAN uses the short frequency band around 2.4GHz for communication, while the ultra-wideband technology uses the frequency band from 3. 1GHz to 10.6GHz for communication. The signal level of UWB is low enough, so the influence of UWB signal is similar to noise for other wireless communication technologies.

At present, the technology widely used in wireless networks is IEEE 802. 1 1 standard, which is Wi-Fi promoted by Intel. This technology is widely used in notebook computers, and even some digital cameras of Nikon and Canon have adopted this technology. Wireless USB technology is a completely different technology. Because it is relatively simple to implement and the power consumption is only half of 802. 1 1, many manufacturers prefer to adopt wireless USB technology.

Ravencraft said that the key to adopting 802.438+0 1 technology for high-end mobile phones and digital cameras is to solve the battery life problem. Manufacturers find that ultra-wideband technology is the best way to solve this problem.

Within 0/0 foot of the computer/kloc-,the transmission rate of the wireless USB device will be maintained at 480M per second. If it is within 30 feet, the transmission rate will drop to 1 100 m per second. However, with the development of technology, the transmission rate of wireless USB will exceed 1G per second or even faster.

At present, UWB technology can be used not only for wireless USB connection, but also for Bluetooth and IEEE 1394 firewire connection, and even for short-distance WiNet connection.

[Edit this paragraph] Different interfaces and data lines of ]USB.

With the popularity of various digital devices, especially MP3 and digital cameras, there are more and more USB devices around us. However, although these devices all use USB interfaces, the data lines of these devices are not exactly the same. These data lines are the same at the end connected to the PC, but when connecting the device end, for the sake of size, various interfaces are usually used.

The connectors of most digital products are the same except those connected to PC, and the other end also follows the standard specifications.

USB is a unified transmission standard, but there are many kinds of interfaces, the most common one is the flat one used by our computer, called port A, which has four wires in it. According to who is plugged in, it is divided into male interface and female interface. Generally speaking, wires are male and machines are female.

●USB A plug port

The picture at the top right is the most common USB A port.

Common Mini B 5Pin interface:

Next is the most common interface in digital products. Due to the limited size of digital products, Mini B interface is usually used, but there are many kinds of Mini B interfaces.

● Mini B 5Pin

The picture on the right shows the Mini B 5Pin interface schematic diagram.

This kind of interface can be said to be the most common interface at present. Because of its excellent anti-misoperation performance and compact size, it is gaining the favor of more and more manufacturers. Now it is widely used in card readers, MP3 players, digital cameras and mobile hard disks.

The picture below shows the Mini B 5Pin interface on Sony F828.

At present, there are Sony cameras, video cameras and MP3 players, Olympus cameras and voice recorders, Canon cameras and HP digital cameras, and so on, and the number is quite large.

Common Mini B 4Pin interface:

In addition to the most common 5-5Pin mini-B interface we have seen before, there are many other mini-B interfaces, some of which are common.

● Mini B 4Pin

The mini-B type 4Pin interface is shown on the right.

The picture below shows the patch cord of mini-B 4Pin interface.

This interface is common in digital products of the following brands: Olympus C series and E series, most of Kodak's digital cameras, Samsung's MP3 products (such as Yepp), Sony's DSC series and Compaq's IPAQ series. ...

Fuji Mini B 4Pin flat interface;

There is another form of Mini B 4Pin, that is, Mini B 4Pin flat. As the name implies, this interface is flatter than Mini B 4Pin, and it is also widely used in devices.

● Fuji Mini B 4Pin tablet

Right: Mini B 4Pin flat connector.

This interface is similar to INI B 4pin mentioned above, but it is flatter and takes up less space.

This interface is common in the following devices: Fuji's FinePix series, Casio's QV series cameras, and Konica's products.

We can see that Fuji machines use this interface more, and almost all the old models use this interface. However, it is worth noting that Fuji has given up this interface on the latest S5000 and S7000 and switched to the Mini B 5Pin camp.

Unique to Nikon, Mini B 8Pin interface:

In addition to the previous 4Pin and 5Pin, there is also an 8-pin mini-B interface, which is rarely seen on other devices, usually on digital cameras. There are also three kinds of mini-B interfaces, one is common, the other is round, and the other is plane interface with 2×4 layout.

● Mini type B 8-pin

On the right is the interface of Mini B type 8Pin.

As far as I know, this interface is only used by Nikon Coolpix 775.

● Mini B 8 pin circle

The picture on the left shows the Mini B 8Pin circular interface.

Compared with the common types before, this kind of interface changes the original D-shaped connector into a circular connector, and designs bumps to prevent it from being inserted by mistake.

This connector can be found in some Nikon digital cameras, and CoolPix series is more common. Although Nikon has always insisted on using this interface, in some newer models, such as D 100 and CP2000, the most popular Mini B 5Pin interface is also adopted.

Almost universal 8-pin 2x4 interface:

In addition to the Mini B 5Pin interface we have seen before, I think everyone must be familiar with the following interface, which was once quite popular.

● Mini b8 pin 2×4

As shown in the figure: Mini B 8Pin 2×4 interface.

This kind of interface is also a common interface, such as iRiver's famous MP3 series, among which 180TC, which is known as the "iron triangle", is adopted by many other products in this series. The application scope of this interface is still relatively wide, but after iRiver changed from 3XX series to Mini B 5Pin interface, this specification is obviously not as eye-catching as Mini B 5Pin.

[edit this paragraph ]USB On-The-Go supplementary standard

Usb portable supplement1.0: 200165438+released in February. Usb Portable Supplement1.0a: It was released in June 2003, which is the current version.

USB OTG is the abbreviation of USB On-The-Go and a technology developed in recent years. Published by USB implementer forum on February 8, 2000118, it is mainly used for data exchange between different devices or mobile devices. Especially PDA, mobile phone and consumer equipment. It changes the inconvenience of data exchange between memory cards with up to seven standards by replacing connectors with different standards among digital cameras, video cameras, printers and other devices.

With the development of USB technology, PC and peripheral devices can connect devices with various data transmission speeds in a simple way and at moderate manufacturing cost. All the applications mentioned above can be controlled by PC, as peripherals of PC, and exchange data through USB bus. However, this convenient exchange method, once you leave the PC, the device can't use the USB port to operate, because no slave device can act as a PC-like host.

On-The-Go, that is, OTG technology is to realize data transmission between slave devices without a host. For example, the digital camera is directly connected to the printer, and through OTG technology, the USB ports seen by two devices are connected to print photos immediately; You can also send the data from the digital camera to the mobile hard disk with USB interface through OTG, so you don't need to carry expensive memory cards or portable computers for field work.

In OTG products, some new functions have been added:

* New standards for designing compact connectors and cables;

* On the traditional peripheral equipment, the host capacity is increased to adapt to point-to-point connection;

* This ability can be dynamically switched between two devices;

* Low power consumption, ensuring that USB can work under battery power supply.

After using OTG, the connection between the original equipment and PC will not be affected, but more than 654.38 billion devices with USB interface on the market can also be interconnected through OTG.

[1] [2] [3] Introduction to USB 3.0

Intel Corporation (Intel) and leading companies in the industry jointly established the USB 3.0 Promotion Group, aiming at developing ultra-efficient USB interconnection technology, which is 10 times faster than today. This technology was jointly developed by Intel, Hewlett-Packard (HP), NEC, NXP Semiconductors and Texas Instruments. Its applications include fast, synchronous and instant transmission of personal computers, consumer products and mobile products. With the increasing popularity of digital media and the increasing number of transmitted files-even more than 25GB, fast synchronous instant transmission has become a necessary performance requirement.

USB 3.0 has backward compatibility standards, and has both the ease of use and plug-and-play function of traditional USB technology. The goal of this technology is to introduce products that are 10 times faster than the current connection level, and adopt the same architecture as wired USB. In addition to optimizing the USB 3.0 specification to achieve lower energy consumption and higher protocol efficiency, USB 3.0 ports and cables can also achieve backward compatibility and support future optical fiber transmission.

"Logically, USB 3.0 will become the most popular wired interconnection method for the next generation of personal computers," said Jeff Ravencraft, a technology strategist at Intel. "The digital age needs high-speed performance and reliable interconnection to realize the transmission of massive data in daily life. USB 3.0 can meet this challenge well and continue to provide the USB usability experience that users have become accustomed to and continue to expect. "

At the beginning of the establishment of the USB 3.0 promotion group, Intel hoped that USB Design Institute (USB-IF) could serve as the industry association of USB 3.0 specification. The complete USB 3.0 specification is expected to be launched in the first half of 2008, and USB 3.0 will initially take the form of discrete chips.

The USB 3.0 promotion group, including HP, Intel, NEC, NXP Semiconductors and Texas Instruments, is committed to protecting the existing USB device driver infrastructure and investment, the appearance of USB and its convenience in use, while continuing to carry forward the function of USB as an outstanding technology.

Phil Schultz, vice president of consumer inkjet solutions at HP, said, "Our support for USB 2.0 and wireless USB technology shows that HP is committed to providing customers with reliable ways to connect peripheral devices. "Now with USB 3.0, we will create a better experience for our customers and connect printers, digital cameras and other peripheral devices with personal computers."

Patrick Gelsinger, Intel's senior vice president and general manager of the digital enterprise department, said: "Intel is at the forefront of the industry in developing and adopting two generations of USB technology, and USB has now become the most popular peripheral interface for computing and handheld electronic devices. "Because the market development supports customers' demand for storing and transmitting huge data, we hope to develop the third-generation USB technology, which can use the existing USB interface and optimize it to meet these needs. "

"NEC has been a supporter of USB technology since the first installation of wired USB," said Katsuhiko Itagaki, general manager of NEC's electronic SoC system division. "It is time to further develop this successful interconnection interface to meet the higher demand of the market for huge data transmission speed, thus minimizing the waiting time of users."

Pierre-Yves Couteau, Director of NXP Semiconductor Business Line Interconnection Entertainment Strategy and Business Development Department, said, "NXP is pleased to join hands with other top companies to promote world-leading interconnection technology to meet the needs of next-generation peripherals. "As a leading supplier of USB semiconductor solutions, NXP is committed to promoting the standardization and application of ultra-high-speed USB."

"With the popularity of high-speed USB in various market segments such as personal computing, consumer electronics and mobile, we expect that USB 3.0 will quickly replace USB2.0 and become the de facto standard in high-bandwidth applications," said Greg Hantak, vice president of global ASIC of Texas Instruments. "Texas Instruments is very excited, and the excellent performance of USB 3.0 will further expand the application field of USB and bring better experience to users."

Universal serial bus implementer forum.

The non-profit organization USB Design Forum (USB-IF) was established to support the development and popularization of USB technology. Through its identification and certification project, USB-IF provides assistance for developing high-quality and compatible USB devices, and also vigorously promotes the advantages of USB and the quality of products certified by USB.

The USB 3.0 standard was officially completed and released.

The USB 3.0 promotion group, which is composed of industry giants such as Intel, Microsoft, Hewlett-Packard, Texas Instruments, NEC and ST-NXP, announced today that the next-generation USB 3.0 standard formulated by the organization was officially completed and publicly released. The new specification provides ten times the transmission speed of USB 2.0 and higher energy-saving efficiency, which can be widely used in PC peripherals and consumer electronics products.

The USB 3.0 standard has been handed over to the USB Implementer Forum (referred to as USB-IF), the management organization of the standard. The organization will cooperate with hardware manufacturers to develop new hardware supporting USB 3.0 standard, but it will take some time for the actual product to go on the market.

The first version of USB 1.0 appeared in 1996, and the speed was only1.5 MB/s; Two years later, it was upgraded to USB 1. 1, and the speed was greatly increased to12mb/s. Up to now, this standard interface can still be seen on some old devices. In April 2000, USB 2.0, which is widely used at present, was launched, with a speed of 480Mb/s, 40 times that of USB 1. 1. Now eight and a half years have passed, and the speed of USB 2.0 has long been unable to meet the application requirements, so USB 3.0 came into being. The maximum transmission bandwidth is as high as 5.0Gb/s, that is, 625MB/s, which is backward compatible when using A-type interface.

The IEEE organization recently approved the new specification IEEE 1394-2008, but the transmission speed of the new version of FireWire is only 3.2Gb/s, which is equivalent to more than 60% of USB 3.0. No wonder manufacturers in industries such as Apple have generally lost interest in this technology.

Based on half-duplex two-wire bus, USB 2.0 can only provide unidirectional data stream transmission, while USB 3.0 adopts double simplex four-wire differential signal lines, so it supports bidirectional concurrent data stream transmission, which is also the key reason for the rapid increase of new specifications.

In addition, USB 3.0 also introduces a new power management mechanism to support standby, hibernation and pause.

Tektronix, a manufacturer of measuring instruments, was the first to announce a testing tool for USB 3.0 last month, which can help developers verify the compatibility between the new specification and hardware design.

USB 3.0 will be called "USB SuperSpeed" in practical equipment application, which conforms to the previous USB 1. 1 full speed and USB 2.0 high speed. It is expected that commercial controllers supporting the new specifications will be listed in the second half of 2009, and consumer products will be listed on 20 10.

USB 3.0 logo

USB 3.0 dual bus architecture diagram

Communication layer and power management characteristics

Standard -A type interface dimension drawing

Standard-Physical Simulation Diagram of Male and Female Ports

Standard b interface dimension drawing

Pico-interface dimension diagram

Cable structure diagram

Schematic diagram of cable cross-section joint

Example of USB 3.0 standard interface and cable

USB 3.0

In addition, USB 3.0 also introduces a new power management mechanism to support standby, hibernation and pause.