1. Application of RS485 to Ethernet RS485 communication technology is used a lot in engineering, and its main advantages are as follows: The wiring is simple: only 2 wires are needed, and now the shielded wire interface of the network cable is generally used. Long communication distance: Due to the use of differential mode communication, the communication distance is longer than RS232. It can support multi-machine network communication: compared to RS232, which can only connect one-to-one, RS485 can mount multiple terminals on the line, and realize multi-machine communication by means of query-response. But RS485 often needs to be converted to Ethernet, that is, to TCP / IP. The main reasons behind analyzing these applications are: Ethernet can be connected to the internet so that long-distance communication can be achieved, and monitoring can be achieved on a global scale, which is not possible with RS485. When multiple RS485 devices are required to connect to the computer, the traditional method is to use multiple serial port cards. That is to use the extended serial port on the computer to achieve multiple RS485 serial ports. After using RS485 to Ethernet, you can leave the RS485 interface to the scene, and only one network cable can be kept at the end of the monitoring computer, which is more convenient to use. 2. RS485 to Ethernet solution The realization of RS485 to Ethernet (that is, 485 to network port) is mainly a hardware converter and a software driver. There are two types of hardware converters: serial server (serial networking server, serial communication server), serial networking module. The RS485 serial server is with a shell, which can connect existing 485 devices to Ethernet. Suitable for the networked transformation of existing RS485 serial devices. The RS485 serial networking module is without a shell, and can be understood as an embedded RS485 to Ethernet module. Using the module solution, the module can be integrated into the user equipment to achieve the integration of the serial server and the device. In terms of price, the module solution is lower than the serial server solution. The two types of hardware are shown below: After using the hardware and software system of the RS485 to Ethernet solution, the user's 485 device is equivalent to the expansion of the network, and the original hardware and software programs do not need to be modified. The hardware of the serial port server realizes the conversion of the RS485 interface to the TCP / IP interface (network interface). Then, with the use of the virtual serial port driver on the computer side, the TCP / IP connection can be virtually converted into a serial port again. The virtual serial port driver can virtualize virtual serial port numbers like COM5 and COM6 in the driver layer of the computer, and bind the remote serial port server to these virtual serial ports. In this way, when the user serial port program opens the virtual serial port, it can communicate with the remote serial port server, that is, communicate with the serial port device. 3. The key technology of RS485 to Ethernet If RS485 is to be seamlessly upgraded to Ethernet, it contains many key technologies. It is necessary to seamlessly combine Ethernet technology and RS485 communication protocol for transition. These include: 9-bit technology, framing technology, master-slave mechanism, etc. 9-bit technology: In 485 mode, users can send 9-bit data. And sometimes the 9th bit is used to indicate whether it is a data frame or an address frame. Since Ethernet is 8-bit data during network communication, there is no space for 9-bit. So how to transfer the 9 bits of 485 becomes a problem. It is understood that Shanghai Zhuo Lan's serial server uses a protocol called realcom, which can convert the 9-bit data format of RS485 into 8-bit data of Ethernet. Framing technology: Framing is a key technology that appears in serial to Ethernet (including RS485 to Ethernet), that is, when the serial server receives data from the serial device, when will the data be packaged and forwarded to Ethernet, if every It is obviously inefficient to pack all bytes into one package, so how many bytes are suitable for packaging. Here, the user needs to set a parameter called the longest packet length and the longest packet interval.
About this project
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