As an engineer, you should often deal with interfaces, so Xiaobian asked Du Niang. The complete definition of interfaces is that entities provide an abstraction to the outside world to separate external communication methods from internal operations, so that they can be modified internally without affecting the way other external entities interact with them, just like the multiple abstractions provided by object-oriented programming.



What a complex feeling. In fact, the interface is an indirect means, so it will cause some additional burden compared with direct communication. In electronic products, there are hardware interfaces and software interfaces: the interfaces between hardware components of information machines such as computers are called hardware interfaces; The interface between computer and other information machine software components is called software interface. The following is a brief introduction to this kind of hardware interface:

 

Introduction to hardware interfaces and common interfaces




Hardware interfaces mainly include:



IDE



The English full name of IDE is “integrated drive electronics”, i.e. “electronic integrated drive”. Its original meaning refers to the hard drive that integrates the “hard disk controller” with the “disk body”. The integration of the disk body and the controller reduces the number and length of cables of the hard disk interface, enhances the reliability of data transmission, and makes it easier to manufacture the hard disk, because the hard disk manufacturers no longer need to worry about whether their hard disk is compatible with the controllers produced by other manufacturers. For users, hard disk installation is also more convenient. IDE, an interface technology, has been developing continuously since its birth, and its performance has been continuously improved. Its characteristics of low price and strong compatibility have created an irreplaceable position for other types of hard disks.



IDE represents a type of hard disk, but in practical applications, people are also used to using ide to call the first ide type hard disk ATA-1. This type of interface has been eliminated with the development of interface technology, and later developed and branched out more types of hard disk interfaces, such as ATA, ultra ATA, DMA, ultra DMA and so on.



SCSI



SCSI is called “small computer system interface” in English. It is a completely different interface from IDE (ATA). IDE interface is the standard interface of ordinary PC, while SCSI is not an interface specially designed for hard disk. It is a high-speed data transmission technology widely used in small computers. SCSI interface has the advantages of wide application range, multitasking, large bandwidth, low CPU occupancy and hot plug, but its high price makes it difficult to popularize like IDE hard disk. Therefore, SCSI hard disk is mainly used in medium and high-end servers and high-end workstations.



Fibre channel



The English spelling of fibre channel is fibre channel. Like SCSI interface, fibre channel is not an interface technology designed and developed for hard disk at first. It is specially designed for network system. However, it is gradually applied to hard disk system with the demand of storage system for speed. Fibre channel hard disk is developed to improve the speed and flexibility of multi hard disk storage system. Its emergence greatly improves the communication speed of multi hard disk system. The main characteristics of fibre channel are: hot pluggability, high-speed bandwidth, remote connection, large number of connected devices, etc.



Fibre channel is designed for multi hard disk system environment such as server, which can meet the requirements of high-end workstation, server, mass storage sub network, two-way and serial data communication between peripherals through hub, switch and point-to-point connection.



SATA



The hard disk using SATA (serial ATA) port is also called serial hard disk, which is the trend of PC hard disk in the future. In 2001, the serial ATA committee composed of Intel, apt, Dell, IBM, Seagate and Maxtor formally established the serial ATA 1.0 specification. In 2002, although the related equipment of serial ATA has not been officially listed, the serial ATA Committee has established the serial ATA 2.0 specification first. Serial ATA adopts serial connection mode. Serial ATA bus uses embedded clock signal and has stronger error correction ability. Compared with the past, its biggest difference is that it can check the transmission instructions (not just data). If errors are found, they will be corrected automatically, which greatly improves the reliability of data transmission. The serial interface also has the advantages of simple structure and supporting hot plug. Serial hard disk is a new type of hard disk interface completely different from parallel ATA. It is well-known for transmitting data in serial mode. Compared with parallel ATA, it has many advantages. First, serial ATA transmits data in a continuous serial manner, and only 1 bit of data is transmitted at a time. This can reduce the number of pins of SATA interface, reduce the number of connecting cables and improve efficiency.

                                

Raid card



Of course, IDE raid also has its disadvantages. For example, it cannot be compared with SCSI raid in terms of CPU utilization and the number of connected devices. At the same time, IDE raid only supports raid0, RAID1 and raid0 + 1, and its performance is slightly inferior to SCSI raid. Therefore, SCSI raid is still the main application of high-performance computers. SATA raid is a newly born raid mode. It is similar to ide raid. Its biggest advantage is low cost. In other aspects, it is also close to ide raid.



Refers to the hard disk interfaces supported by the raid card, mainly including IDE interface, SCSI interface and SATA interface.



RAID technology was based on SCSI interface when it came out. Because of its high cost, it is mainly oriented to high-end applications such as servers. Ordinary users have no chance to have raid at all. With the popularization of computers, it drives the unprecedented prosperity of PC computers. Accordingly, driven by the market, the price of IDE interface equipment for PC computer is greatly reduced and the performance is greatly improved. In view of this, RAID technology began to be transplanted to IDE interface, and launched a raid application based on IDE interface, which is called ide raid. The raid application based on SCSI interface is called SCSI raid. Compared with SCSI raid, IDE raid has extremely low price and no inferior performance. Accordingly, IDE raid solution has high cost performance that SCSI raid can’t compare. Therefore, IDE raid has been widely welcomed by ordinary PC users and ordinary commercial applications since its launch.



MD equipment



The MD device interface (called port by Hong Kong and Taiwan) refers to the input and output interfaces of MD (mini disc) products. First of all, as an MD product, the output interface of the headset is naturally necessary. In addition to the basic headphone output interface, the recording and playback products should also have a line input interface, so that the MD can be connected with other playback devices, the played audio can be input into the MD and recorded on the MD film. Netmd products should also have a USB interface, so that they can be connected to the computer to transfer files. Some products also have a microphone interface, which can record external sound through MD.



USB interface



It is a technology developed for transmitting data between PC and digital equipment. Standard USB, Mini USB (typical application: MP3) and micro USB (typical application: Android smartphone) have become the most common USB interfaces. It is widely used in information and communication products such as personal computers and mobile devices, and extended to photography equipment, digital TV (set-top box), game consoles and other related fields. USB has developed from USB 1.0 to the latest USB 3.1. USB 3.1: the transmission speed is 10Gbit / s, the three-stage voltage is 5V / 12V / 20V, the maximum power supply is 100W, and the new type-C plug-in is no longer divided into positive and negative.



USB type-C interface



The biggest feature of type-C double-sided pluggable interface is that it supports double-sided insertion of USB interface, which formally solves the worldwide problem of “USB can never be inserted”, and the front and back sides can be inserted casually. At the same time, the USB data cable used with it must also be thinner and lighter. It is a type-C PD chip manufacturer: microchip, cypress, NXP, Rohm, technology leading semiconductor, power integration, etc.



The following are common interfaces:



Infrared interface: it is a communication scheme with low cost, short distance, no connection, low power consumption and strong confidentiality. It is mainly used in wireless data transmission in PC, but it has gradually been applied in wireless network access and short-range remote control home appliances. In view of the many advantages of infrared communication, almost all current motherboards provide infrared interfaces so that users can use it to communicate with devices with infrared interfaces, such as laptops, printers, modems, handheld computers, mobile phones, etc. However, the computer motherboard only provides an infrared interface and does not provide a complete transmitting and receiving device, so users still need to buy an infrared connector when they want to use infrared communication.



DB interface: D-type data interface, which is the interface standard for connecting electronic equipment (such as computer and peripherals). Because the shape is similar to the English letter D, it is named D-type interface.



PCI interface: it is the most widely used interface in personal computers. Almost all motherboard products have this slot. PCI slots are also the type with the largest number of slots on the motherboard. On the popular desktop motherboard, the motherboard with ATX structure generally has 5 ~ 6 PCI slots, while the smaller mATX motherboard also has 2 ~ 3 PCI slots, which shows its wide application.                                 

               

Serial interface: serial port, also known as “serial port”, also known as serial communication interface (usually COM interface), is an expansion interface using serial communication mode. Common are RS-232 for general computer applications (using 25 pin or 9-pin connectors) and half duplex RS-485 and full duplex RS-422 for industrial computer applications.



RS-232 is one of the mainstream serial communication interfaces. RS-422 interface, the full name of the standard is “electrical characteristics of balanced voltage digital interface circuit”, which defines the characteristics of the interface circuit. A typical RS-422 is a four wire interface. In fact, there is also a signal ground wire, a total of 5 wires. Its DB9 connector pin definition. RS-485 interface is developed from RS-422, so many electrical regulations of RS-485 are similar to RS-422.



PS / 2 interface: PS / 2 interface is a 6-pin circular interface, and 2 pins are idle. PS / 2 is one of the common interfaces on earlier computers. It is used for mouse, keyboard and other devices. Generally, the mouse of PS / 2 interface is green and the keyboard is purple. The PS / 2 interface is an input device interface, not a transmission interface. Therefore, the PS2 port has no concept of transmission rate at all, only scanning rate.



Dock interface (typical application: Apple series products): the dock interface has 9pin and 30pin. Apple started using the 30pin dedicated dock interface on the iPod 10 years ago, and almost all data synchronization and peripherals rely on this interface. Since Apple launched the 9 pin lightning dock interface when the iPhone 5 was released, the release of the new interface standard also means that the 30 pin dock interface that Apple has used for 9 years will be officially replaced.



RJ11 interface (typical application: telephone): general network telephone will provide two RJ-11 interfaces. One RJ-11 interface is used to connect the telephone line connected with the HomePNA switch, and the other RJ-11 interface is connected with the telephone.



RJ45 interface (typical application: network cable): RJ45 interface is usually used for data transmission, and the most common application is network card interface.



Radio frequency interface (TV interface): TV interface is also known as RF RF input interface. Radio frequency (RF) interface is used for antenna and analog closed-circuit connection TV. As the most common video connection, it can transmit analog video and audio signals at the same time. The RF interface transmits the mixed coded signal of video and audio. The circuit of the display device separates and decodes the mixed coded signal in a series of steps before outputting the image. Due to the need for mixed video and audio coding, the signals will interfere with each other, so its image quality output quality is the worst of all interfaces. Cable and satellite TV receiving equipment also commonly use RF connection, but in this case, they transmit digital signals.



AV interface: AV interface transmits video and audio separately, so as to avoid mutual interference between audio and video. However, due to the need to decode and display the brightness and chroma in video transmission, there is still a loss in video transmission, so the current HD video playback basically gives up the AV interface.



Din interface: s terminal is also called mini DIN interface in the name of some projector manufacturers, including 4-core (without sound output), 5-core, 6-core, 7-core, 8-core, 9-core (capable of providing signal output of 6 channels) and other different products are used on projectors.



VGA interface: VGA terminal V (other names include RGB terminal, D-sub 15, or mini D15) on notebook computer is a 3-row 15 pin de-15. VGA terminals are usually used in computer display cards, monitors and other devices. It is used to transmit analog signals.



DVI interface: digital video interface, that is, digital video interface. The digital display working group (ddwg) established at the Intel Developer Forum in September 1998 invented a high-speed digital signal transmission technology, which has three different interface forms: dvi-a, DVI-D and dvi-i. DVI-D only has digital interface, and DVI-I has digital and analog interfaces. At present, DVI-I (24 + 5) is mainly used.



HDMI interface: high definition multimedia interface is a digital video / audio interface technology. It is a special digital interface suitable for image transmission. It can transmit audio and image signals at the same time, and the maximum data transmission speed is 2.25gb/s.                                 

               

BNC interface: BNC, the full name is bayonet nut connector (bayonet nut connector, which vividly describes the shape of this connector), also known as British naval connector (British Navy connector, which may be the earliest use of this connector by the British navy) or bayonet Neill conselman (Neill conselman bayonet, which was invented by a man named Neill conselman).



RCA analog audio: RCA connector is often called lotus head. Using RCA cable to transmit analog signal is the most common audio connection at present. Each RCA cable is responsible for transmitting the audio signal of one channel, so a pair of cables are required for stereo signal. For multi-channel system, the same number of cables should be equipped according to the actual number of channels. For stereo RCA Audio Interface, the right channel is generally marked with red, and the left channel is marked with blue or white.



S / PDIF interface: the full name of S / PDIF is Sony / Philips Digital interconnect format, which is a civil digital audio interface protocol jointly developed by Sony and Philips. Because it is widely used, it has become the de facto civil digital audio format standard. A large number of consumer audio digital products such as civil CD player, DAT, MD machine and computer sound card digital port support s / PDIF, and there are also interfaces of this standard on many professional equipment.



XLR interface: XLR, commonly known as XLR head, is composed of three pin plug and locking device. Due to the locking device, the XLR connection is quite secure. The large three core interface adopts a plug with a diameter of 6.35 mm, which has the advantage of wear resistance and is suitable for repeated plugging. Balanced analog audio connection mainly appears on advanced analog audio equipment or professional audio equipment.



SM card interface: the full name of SM card is smart media, which was launched by Toshiba Toshiba in 1995. The SM card itself has no control circuit, so it is smaller. Many old cameras use SM memory card. Because its control circuit is designed in digital equipment, the compatibility problem is prominent. Gradually eliminated.



MMC card interface: the full name of MMC card is multimedia card, which was launched by SanDisk and Siemens in 1997. It can be seen in all kinds of portable devices. Later upgraded RS-MMC (reduced size MMC), MMC micro card (Samsung standard, 10PIN pin, self use), etc. It is said that there are also high speed MMC, mmcplus and mmcmobile.



SD card interface: the full name of D card is secure digital memory card, which was launched by Toshiba Toshiba, Panasonic and SanDisk in 1999. It has high capacity, high data transmission rate and writable protection. Pin 9pin. The SD card specification is developed from MMC and is about the same size as MMC. The SD card maintains upward compatibility with MMC card. The SD card retains the 7-pin pin of MMC and expands the 2-pin data line. SD cards are also available in low speed and high speed. High speed SD card is also called SDHC. At present, 4G SD cards are basically SDHC.



XD card interface: the full name of D card is XD picture card. XD is also the abbreviation of extreme digital. It is jointly launched by Fuji and Olympus. It is specially used for digital cameras. One side 18pin pin pin. The theoretical maximum capacity of XD card can reach 8GB, with great expansion space. At present, XD cards on the market have different capacity specifications such as 16 / 32 / 64 / 128 / 256MB. The figure below shows Olympus 1g XD card with obvious XD logo in the middle.  

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