The realization of multiplexing conversion from serial communication to Ethernet
1 Introduction
A device has four light guide liquid level secondary meters. According to the process requirements, the secondary meter display needs to be transformed into DCS monitoring. The light guide liquid level secondary meter can only output RS-485 serial signals, and the monitoring operation station requires simultaneous monitoring. Therefore, the technical essence of this system is to realize the conversion of multi-channel serial communication to multi-channel Ethernet communication.
2 Design plan
2.1 Simple solution
Serial communication (whether RS-232 or RS-485) is just point-to-point communication, so 4 light guide liquid level secondary meters can be connected to one operation server, and the other three operation clients can get data from the operation server. This can meet the above requirements, as shown in Figure 1.
Figure 1 Schematic diagram of the server-client mode scheme structure
However, for security reasons, the operation of the server has obviously become the bottleneck of the system. Once a server failure occurs, the system will be paralyzed, which is not allowed by the process. Therefore, many-to-many communication conversion must be performed.
2.2 Multi-channel communication conversion scheme
ICP DAS's Internet communication controller I-7188E5D-485 is used as the multi-channel protocol conversion communication controller. It can realize the conversion of 4 to 4 serial to Ethernet communication through programming. The other two operating stations use the server / client approach. This has reached fourfold
Redundancy can fully guarantee the uninterrupted operation of the system. as shown in picture 2
Figure 2 Schematic diagram of the multiplex conversion system
2.3 Characteristics of communication controller
The Internet communication controller I-7188E5D-485 is mainly for communication applications. According to different embedded configurations and applications, the Internet communication controller can be used as a device server, or as an addressable Ethernet to RS-232 / 485/422 converter, or as an embedded Internet / Ethernet Controller.
(1) Addressable Ethernet to RS-232 / 485/422 converter
Most RS-232 / 485/422 devices do not support device addresses. The I-7188E5 D-485 can assign a unique address to any RS-232 device installed on the RS-485 network. The host sends a command with this device address to the RS-485 network. The I-7188E5 D-485 as the target unit will remove this address segment and send the rest of the command to its local corresponding RS-232 device. And the response of this local corresponding RS-232 device should also be transmitted to the host through the I-7188E5 D-485 as the target unit.
(2) Device server from Ethernet to RS-232 / 485/422
A device server is a device that connects any device with a serial communication port via a network. Because I-7188EN has an independent operating system, independent protocol, small size and its flexibility, such a device server can meet all the requirements of actual network use. Most devices do not have network ports, and our Internet communication controller makes them accessible to the network.
(3) Internet communication controller I-7188E5D-485 also includes: CPU: 80188-40 or compatible chip; 10BASE-T NE2000 compatible Ethernet controller; repeatable download; remote configuration and diagnosis; built-in unique 64-bit hardware Serial number; COM port driver supports interrupt and 1k sequence buffer; built-in RTC, NVRAM, EEPROM; built-in self-tuner ASIC chip; 1 RS-232 communication port and 4 RS-485 communication ports; 7-segment LED display; Built-in MiniOS7; program download: COM1 and Ethernet.
3 Monitoring software
The host monitoring software selects Kingview V6.5 from Beijing Yakong.
Kingview has basic functions such as variable definition and management, flowchart display, alarm and event management, historical trends, system security management functions, and reporting system.
Kingview also supports network OPC function. Kingview and Kingview can communicate in OPC mode through the network. Similarly, other OPCclient / OPCserver can also communicate with Kingview in network through OPC mode. Therefore, the functions of operating the server and operating the client can be completely realized.
Therefore, the specific uniformity of the entire system software: only need to purchase a development version; all project files can be fully shared. The six operating stations operate completely independently, and are physically four redundant.
4 Conclusion
The technical difficulties of this project are: to implement the principle of safety first and reliability in structural design; the programming of multiplex communicators is a relatively complex task. Through the actual application on site, the expected results have been achieved. Is a successful high-performance low-cost case.
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