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          Application of serial port server in broadcast monitoring

          1. System principle

          The RS-232 interface is called serial port, asynchronous port or a COM port, and is the interface between DTE (data terminal equipment) and DCE (data communication equipment). DTE includes computers, terminals, serial printers and other equipment. RS-232 is defined as a single-ended standard that increases communication distance in low-rate serial communications. RS-232 adopts unbalanced transmission method, so-called single-ended communication. The RS-232 serial port uses level mode for data transmission, and the transmission distance is generally short, so RS-232 is only suitable for communication between local devices.

          At present, the more commonly used serial ports are 9-pin serial port (DB9) and 25-pin serial port (DB25), which can be directly connected to the standard RS-232 port (RS-422, RS-485 remote) with a cable. The most simple and commonly used is the three-wire connection method, that is, the three pins of grounding, receiving data and sending data are connected. This article only involves the most basic connection method, and is directly connected by RS232.

          DB9 commonly used pins description Serial data transmission can be achieved as long as there are data receiving pins and sending pins. For 9-pin serial port and 25-pin serial port, 2 and 3 are directly connected. The above table is for the standard serial port of a microcomputer. For many non-standard devices, one principle: the receiving data pin (or line) and the sending data pin (or line) are connected, cross each other, and the signals are correspondingly connected.

          DB9 common pin description

          Due to the short transmission distance of RS-232, it is not possible to connect long-distance devices, and devices with serial port (RS-232) management functions cannot perform network management and data access. At this time, we can use advanced TCP / IP Technological and management methods are used to transform these devices. The serial port server is a communication interface converter for data conversion between RS-232 / 485/422 and TCP / IP. It provides two-way transparent transmission of data between the RS-232 / 485/422 terminal serial port and the TCP / IP network. Multiple serial devices are connected and can select and process serial port data streams, convert the existing RS-232 interface data into IP port data, and then perform IP management and IP data access.

          It internally integrates ARP, IP, ICMP, TCP, UDP, DHCP, SOCK5 and other protocols, supports gateways and proxy servers, and parameters can be set through a browser. Supports point-to-point and point-to-multipoint connections, and supports broadcast or multicast methods. Different serial ports can be configured into different modes to meet different application requirements.

          The serial server mainly has the following three working modes:

          Use virtual serial communication mode (Tcp realport): In this mode, one or more converters establish a connection with a computer to achieve two-way transparent transmission of data. The following converters are managed by the virtual serial port software on the computer, and one virtual serial port corresponds to multiple converters, and N virtual serial ports correspond to M converters (N <= M). This mode is suitable for connecting RS232 devices with serial devices controlled by a computer.

          Based on network communication mode (Tcp / Udp socket): In this mode, the application program on the computer writes a communication program based on the SOCKET protocol, and directly supports the SOCKET protocol on the converter settings. The serial server completes a connection-oriented RS232 link and storage control for communication data between connectionless Ethernet. The system processes various data, processes the serial data stream from the serial device, and performs format conversion to make It becomes a data frame that can be propagated in Ethernet; the data frame from Ethernet is judged and converted into serial data and sent to the serial device that responds.

          Point-to-point communication mode (PPP): In this mode, the converters are used in pairs, one as a server and one as a client, and a connection is established between the two to achieve two-way transparent transmission of data. This mode is suitable for transforming the bus connection between two serial devices into a TCP / IP network connection.

          2. System Application

          In the previous centralized monitoring system for broadcast transmission and transmission, data transmission is generally performed through Modem and so on. With the development of network technology and the popularization of the network in the broadcasting industry, remote monitoring and remote data collection through LAN and Ethernet have become the most economical and reliable way. We can realize the connection between the serial device and the network without knowing the complicated TCP / IP protocol and without changing the user program.

          This article takes Kanghai NC600 serial server as an example to discuss the design scheme of the centralized monitoring system of the equipment in the broadcast transmission room and the data acquisition system covered by the broadcast frequency modulation.

          The system structure of the LAN-based centralized monitoring and WAN remote data collection using the serial server is as follows. The monitoring center is responsible for communicating with the field devices to receive various field device information and control the field devices, and at the same time remotely monitor and control each frequency modulation coverage point device through Ethernet. Topology structure is as follows:

          In the practical application of the following serial server, we take Kanghai NC600 as an example.

          1. Network equipment detection

          The supporting software of serial server such as "VSPM Virtual Serial Port" has advanced network detection function. No matter how many serial server devices are in the local area network, they can be scanned within 1 ~ 2 seconds and displayed to the user in detail. It only takes two mouse clicks to map the remote device port to the virtual serial port of the machine. There is no need to enter any serial server data in the whole process. The parameters of the virtual serial port are automatically synchronized with the serial server. After the software is installed, users can find the serial port management software in the control panel of the XP operating system.

          2. There are three ways to enter the serial server to set up

          First, login via WEB browser: directly input the IP address of the serial server.

          Second, remote login via TELNET: If the serial server and the PC used for monitoring are not on the same network segment, you can connect the PC to the serial server by adding a route.

          Assumption: NC600's IP address: 192. 168. 0. 233 XP system IP address: 24. 0.46. 144 Run under DOS command: route add 192.168.0.2324.0.46.144 third, use The serial terminal manages the serial server locally via the CONSOLE port. Connect the serial port of the terminal with the CONSOLE port of NC600. The baud rate of the terminal is 9600, the data bit is 8, the stop bit is 1, and there is no check.

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          亚洲 欧美 图片 自拍 视频
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