1. Using RS485 communication technology, there are many practical applications of converting RS485 to Ethernet, especially in the engineering is more widely used, the advantages in engineering are as follows:
Wiring is very simple: only two wires can be used, the current common use of network cable with shielded wire interface.
Longer communication distance: compared to RS232; RS485 communication distance is too far, thanks to the RS485 using a differential mode communication method.
① Widely compatible with multiple servers for networking communication:
RS485 can connect or mount multiple server terminals at the same time, wait for the query and can respond in detail to complete the way to maintain communication with multiple server terminals.
Compared with only one-to-one RS232, RS485 can achieve twice the result with half the effort.
② RS485 needs to be converted to Ethernet from time to time, analyse the reasons:
Ethernet can be implemented globally in the implementation of long-distance communication and data communication monitoring, are because Ethernet can be connected to the Internet; and RS485 can not be directly connected to the Internet; and RS485 can not be directly connected to the Internet.
And RS485 can not be directly connected to the internet, if you want to connect to the Ethernet must be done through the transmission medium to work.
When the need for multiple connections to the computer, only the traditional solution: the use of multiple serial cards, and RS485 devices can not cope.
Simply put, that is, in the use of more than one RS485 serial port at the same time, the computer also need to expand out more than one serial port to correspond to the RS485 serial port, more troublesome, but also a waste of resources.
After RS485 to Ethernet, there will be stub data, and if you want to save the stub data to the computer server, you need to keep a network cable at the end of the monitoring computer, so you can leave the stub data of the RS485 interface in the same place, and it is more convenient to use it again. 2.
2. In the implementation of RS485 to Ethernet before the specific solution, the need for a software driver and a hardware converter:
And the hardware converter is divided into two kinds: serial port server (serial port communication server that is serial port networking server), serial port networking module.
RS485 serial port server is “dressed” (with a shell), can make 485 devices indirectly connected to the Ethernet, very consistent with the existing RS485 serial devices for the transformation of the network.
RS485 serial networking module is “not wearing clothes” (without a shell), ERS485 serial device is equivalent to the embedded way of RS485 to Ethernet module.
Using the module form to solve the problem, the module can be packaged and transferred to the user’s equipment, so that the data is transmitted in a timely manner, the formation of a serial port server and the integration of equipment.
The hardware RS485 interface of the serial port server and the computer TCP/IP interface (network interface) server is a perfect conversion, so it is used interchangeably. Conversely the virtual serial port server can then drive the computer TCP/IP virtually transformed into a serial port again.
The driver of the virtual serial port can bind the remote serial port server with these virtual serial ports, and can virtualise the virtual serial port number like COM5, COM6, etc. in the driver layer of the computer.
The user serial port program to open the virtual serial port program, in order to communicate through the remote serial port server, so as to complete the serial device data transfer communication.
Using a combination of software and hardware system solutions to achieve the advantages of RS485 to Ethernet: the user’s 485 devices indirectly achieve the expansion of networked information, you can make the original hardware and software programs do not need to modify.
3. RS485 to Ethernet key technologies RS485 to be seamlessly upgraded to Ethernet, which contains a number of key technologies, the need for Ethernet technology and RS485 communication protocols to seamlessly combine the transition.
These include: framing technology, 9-bit technology, master-slave mechanism. The following is a brief description: ① master-slave mechanism, ② framing technology, ③ 9-bit technology.
① Master-slave mechanism:
For the interconnection architecture of slaves and multiple host buses, the role of decoders is very critical.
The port of the host has three decoders, they are: write address channel, write data channel and read address channel decoder.
Their role is to convert: the information of the internal registers and the information of the channel to each other.
The port of the slave is the write response and read data channel will have decoder.
The decoder ensures that one side can be transmitted to the other directions.
This design can be customised. If you know the details and contents, it is not necessary to use the decoder.
② Split-frame technique:
The use of split-frame technology allows the serial port server to receive data from the serial port device.
When will the data packet forwarding to the Ethernet, if each byte is typed as a packet is obviously too inefficient, then how many bytes packet when
Users need to set a length called the longest packet length and the distance between the longest packet interval.
On the other hand, if the data is packaged in the conversion to Ethernet, then each byte is typed into a packet, then it will make the efficiency greatly reduced, and so many packets to when it can be completed! So the split-frame technology solves this problem.
③ 9-bit technology:
Due to network communication, Ethernet is 8bit data space, and there is no 9bit can be placed in the space, so how to make the 485 9bit data transmission to each other has become a major problem.
By using 9-bit technology, users can send 9-bit data space, and sometimes use the 9th bit to represent either the address frame or the data frame.