Communication interface (communication interface ) is the interface between the central processing unit and the standard communication subsystem. For example: RS232 interface. RS232 interface is the serial port, the rear of the computer chassis 9-core socket, next to the general "|O|O|" kind of logo.
Major classifications
The general chassis has two, new chassis may have only one. Laptops may not have one.
Many industrial instruments use it as a standard communication port. The content and format of the communication is usually attached to the user manual of the instrument.
The transfer of data between a computer and a computer or a computer and a terminal can be done in both serial and parallel communication. Because the serial communication method has the use of less lines, low cost, especially in the remote transmission, to avoid the inconsistency of the characteristics of multiple lines and is widely used. In serial communication, both sides are required to use a standard interface, so that different devices can be easily connected for communication. The RS-232-C interface (also known as EIA RS-232-C) is one of the most commonly used serial communication interfaces. It was developed in 1970 by the Electronic Industries Association of America (EIA) in conjunction with the Bell System, modem manufacturers and computer terminal manufacturers **** with the development of standards for serial communications. Its full name is "data terminal equipment (DTE) and data communications equipment (DCE) between the serial binary data exchange interface technology standard" the standard provides for the use of a 25-pin DB25 connector, the connector's signal content of each pin to be specified, but also on the various signal levels to be specified.
With the development of electronic technology and market demand, a variety of various types of instrumentation is increasingly used in various different areas of automation control equipment and monitoring systems, which requires that the system as well as the various components of the system itself must maintain good communication between the completion of the collection of data transmission, advanced communication protocol technology can reliably ensure that this point.
Communication protocol is the agreement between the two sides of the communication, the data format, synchronization, transmission speed, transmission steps, check and correct the error mode and control character definition and other issues to make a unified provision, the two sides of the communication must *** with the same to comply with the realization of the different equipment, different systems of communication between each other. Reasonable application of communication protocols in the development of new products, not only to make the product design more flexible, more convenient to use, but also to expand the scope of use of the product, enhance the competitiveness of the product market.
Several common communication interfaces
1, the standard serial port (RS232)
232 communication line is simple, as long as a cross-wire can be point-to-point bidirectional communication with the PC host. The cable cost is low, but the transmission speed is slow, not suitable for long-distance communication. Consumer PCs are also gradually canceled the interface, currently exists in the industrial control machine and part of the communication equipment.
After installing the system and the necessary drivers, the serial port of the industrial computer can be used directly, and there are many popular serial port debugging tools on the Internet that can be used to test the instrument. It is also relatively easy for users to develop the communication program twice.
2, GPIB
GPIB's most important feature is that a bus can be used to connect a number of instruments to form an automatic test system. The communication rate is low, commonly used to send control commands, applicable to the laboratory or production site with slight electrical interference. Since ordinary PCs and industrial controllers rarely provide GPIB interfaces, it is necessary to purchase a special control card and install the driver to communicate with the instrument.
3, Ethernet
At present, most of the equipment is equipped with LAN network interface, commonly known as "crystal head", which is characterized by flexible networking, multi-point communication, transmission distance is not limited, high speed and other advantages, so that it has become the mainstream of communication.
The role of the interface itself is mainly used for the router to connect with the LAN. However, there are various types of LANs, so this also determines that the type of LAN interface of the router may also be varied. Different networks have different interface types. The common Ethernet interfaces are mainly AUI, BNC and RJ-45 interfaces, as well as FDDI, ATM and fiber optic interfaces. In the instrument industry or system integration industry, most engineers will also choose to write commands through the network interface to do control of the instrument.
4, USB
As the most commonly used interface, USB is only four wires, two power two signals, signals are transmitted serially, so the USB interface is also known as the serial port, the interface output voltage and current is +5V 500mA In fact, there is an error, the maximum can not be more than +/-0.2V, that is, 4.8-5.2V.
The four wires of the USB interface are generally distributed as follows: black line: gnd red line: vcc green line: data+ white line: data- The main role of the USB is to store the data within the device or device through the USB interface to read external information to identify; in addition, USB is also an effective interface to do secondary development. Although USB3.0 technology has been applied in the field of laptop computers and other very mature, but in the field of instrumentation, subject to the processing speed and architecture of the impact of the most common or USB2.0 technology.
5, wireless
In addition to common communication interfaces, wireless connection is also a very important means of communication, which is characterized by: no physical line connection, fast transmission rates, there are many instruments and equipment directly built-in internal 802.11 wireless interface.
You can connect the instrument to a wireless router, or to a cell phone's WIFI hotspot to form a network.
6, multi-machine synchronization interface
In fact, the multi-machine synchronization interface is different from the above mentioned USB, LAN and other common communication interfaces, but the power analyzer class of equipment to ensure that simultaneous measurements to get the number of channels designed to add more interfaces. By connecting the two instruments through the cable, you can test multiple models at the same time, ensuring the synchronization of signal testing.