The communication interface (communicaTIon interface) refers to the interface between the central processing unit and the standard communication subsystem. Such as: RS232 interface. The RS232 interface is the serial port, the 9-pin socket on the back of the computer case, and there is usually a “|O|O|†like the logo.
Main classificationThere are two general chassis, and there may be only one new chassis. There may not be a laptop.
There are many industrial instruments that use it as a standard communication port. The content and format of the communication is generally attached to the user's manual of the instrument.
The data transfer between the computer and the computer or between the computer and the terminal can be performed by serial communication and parallel communication. Since the serial communication method has less use lines and low cost, especially in remote transmission, it is widely used because it avoids inconsistencies in multiple line characteristics. In serial communication, both communication parties are required to adopt 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 currently the most commonly used serial communication interface. It was developed in 1970 by the Electronic Industries Association (EIA) in conjunction with Bell Systems, modem manufacturers, and computer terminal manufacturers for serial communication standards. Its full name is "the serial binary data exchange interface technology standard between data terminal equipment (DTE) and data communication equipment (DCE)". The standard specifies a 25-pin DB25 connector for each connector of the connector. The signal content of the foot is specified, and the levels of various signals are also specified.
With the development of electronic technology and the needs of the market, various types of instruments are increasingly used in various automation control equipment and monitoring systems in different fields, which requires various components between systems and each system itself. The communication must be maintained to complete the transmission of the collected data, and advanced communication protocol technology can reliably guarantee this.
The communication protocol is an agreement of both parties to the communication. The data format, synchronization mode, transmission speed, transmission procedure, error detection mode, and control character definition are uniformly defined. The two parties must comply with each other to implement different devices and systems. Communicate with each other. Reasonable application of the communication protocol to the development of new products not only makes the design of the product more flexible, but also makes it easier to use, and can also expand the scope of use of the product and enhance the competitiveness of the product market.
1, standard serial port (RS232)
The 232 communication line is simple, and only one cross line can perform point-to-point two-way communication with the PC host. The cable cost is low, but the transmission speed is slow and it is not suitable for long-distance communication. Consumer PCs have gradually eliminated the interface, and currently exist in industrial computers and some communication devices.
After the system is installed and the necessary drivers are installed, the serial port can be used directly. There are also many popular serial debugging tools available on the network for testing instruments. The user's secondary development of the communication program is also relatively simple.
2, GPIB
The biggest feature of GPIB is that it can connect several instruments with one bus to form an automatic test system. This communication rate is low and is often used to send control commands for laboratories or production sites where electrical interference is minor. Since ordinary PCs and industrial PCs provide less GPIB interface, it is necessary to purchase a dedicated control card and install a driver to communicate with the instrument.
3, Ethernet
At present, most devices are equipped with a LAN network interface, commonly known as "Crystal Head". This feature is flexible networking, multi-point communication, unlimited transmission distance, high speed, etc., making it the mainstream communication method.
The interface itself is mainly used to connect the router to the LAN. However, the types of LANs are various, so this determines that the router's LAN interface type may also be diverse. Different networks have different interface types. Common Ethernet interfaces mainly include AUI, BNC, and RJ-45 interfaces, as well as FDDI, ATM, and fiber interfaces. These networks all have corresponding network interfaces. In the instrument industry or system integration industry, most engineers also choose to control the instrument through the network port write command.
4, USB
As the most commonly used interface, USB has only 4 wires, two power supplies and two signals. The signal is serially transmitted. Therefore, the USB interface is also called serial port. The output voltage and current of the interface are +5V 500mA. The error, the maximum can not exceed +/-0.2V is 4.8-5.2V.
The four lines of the USB interface are generally allocated as follows: black line: gnd red line: vcc green line: data+ white line: data- USB is mainly used to store data in the device or the device performs external information through the USB interface. Read recognition; in addition, USB is also an effective interface for secondary development. Although the technology of USB3.0 has been very mature in the field of notebook computers, but in the field of instrumentation, it is still the USB2.0 technology that is affected by the processing speed and architecture.
5, wireless
In addition to the common communication interface, wireless connection is also a very important communication method. Its characteristics are: no physical line connection, fast transmission rate, and many instruments have built-in 802.11 wireless interface directly inside.
The instrument can be connected to the wireless router or connected to the WIFI hotspot of the mobile phone to form a network.
6, multi-machine synchronization interface
In fact, the multi-machine synchronization interface is different from the common communication interfaces such as USB and LAN mentioned above, but the power analyzer-type device is designed to ensure that the number of channels is increased and the interface is designed. By connecting two instruments through a cable, multiple models can be tested at the same time, ensuring the synchronization of the signal test.
to sum up
1. In the case where the communication rate is not high, no long-distance communication is required, and only one host or one instrument exists, the serial port can start measurement faster;
2. When it is necessary to connect with the calibration source, signal generator and other instruments at the same time, and they all provide GPIB interface, the communication mode of the device can be changed to GPIB, which can form a small network;
3, Ethernet interface is our recommended connection method, short-distance communication can be directly connected to the industrial computer, or laptop computer with a twisted pair. In the long-distance communication, the switch can also be added to realize one host to control multiple instruments;
4. In some special occasions, when there is no condition for wired communication, the wireless communication interface unique to the far-end PA2000mini and PA8000 series power analyzers can be used. For example, when a colleague and a customer are measuring in a motor vehicle tractor, the power analyzer and the PC host are simultaneously connected to the mobile phone WIFI hotspot, and then the instrument is remotely operated wirelessly on the PC host;
5. The PA series power analyzer has built-in FTP server. After the Ethernet or wireless connection is established, it can be accessed through the browser of the PC host or mobile phone, and the measurement data stored in the instrument can be directly downloaded to the PC host hard disk or the mobile phone storage space. in.
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