Technical overview of serial Ethernet communication
At present, industrial Ethernet technology is a research hotspot in the field of industrial control. Compared with the traditional control network, industrial Ethernet has many advantages, such as wide application, supported by all programming languages, rich hardware and software resources, easy to connect with the Internet, and seamless connection between office automation network and industrial control network. Because of these advantages, especially its seamless integration with information transmission technology and transmission bandwidth unmatched by traditional technologies, Ethernet has been recognized by the industry.
Traditional communication methods usually use RS232, RS485 or RS422 to achieve, but with the development of the network and the improvement of application requirements, the shortcomings of traditional serial communication are increasingly prominent, such as: short communication distance, low speed, low reliability, poor network characteristics, the need for special wiring and so on. Ethernet communication can solve the shortcomings of serial communication well. With the long-term and stable development and maturity of Ethernet technology, it has become the mainstream communication mode in the local area network, and Ethernet is also the main part of the Internet, the use of Ethernet technology, can also be convenient to achieve Internet remote communication.
In order to upgrade serial communication, serial Ethernet technology came into being. With the maturity and development of this technology, serial devices can also be well adapted to network communication, give play to the advantages of network communication, and adapt to higher needs.
2. Serial Ethernet technology introduction
Serial Ethernet conversion equipment and modules, because taking into account the existing serial network, communication mode, as well as entering the Ethernet network there are various new situations (such as IP address allocation, domain name resolution, network security, network performance), so need to apply a lot of new technologies, we take a product on the market serial Ethernet products as an example, to introduce these technologies.
Guangzhou Zhiyuan Electronics Co., Ltd. developed ZNE series embedded network module and NETCOM series serial port server Ethernet products, accumulated many years of experience, make good use of advanced Ethernet technology, fully consider the application needs of this conversion, has advanced technical characteristics in serial Ethernet technology, So that the user can more convenient, faster, more assured his serial device access to the Ethernet, improve the value of the system.
Here are some of the most representative technologies:
2.1 Seamless Upgrade
For existing serial communication networks (or individual serial devices), how to upgrade to the network at the lowest cost is a problem worth considering: existing devices are not easy to re-add circuits, newly developed products do not have the time and energy to develop network interfaces, and it is best to have a way to make everything look like the previous serial port, but also use Ethernet.
This technology is the virtual serial port technology, which encapsulates the serial port communication in the network, and realizes the mapping of the network to the serial port through the windows host computer driver, so that users can use the network serial port like using the real serial port.
ZNE/NETCOM series support virtual serial port mode, do not need to change the device code, do not need to modify the writing machine software, as long as the use of ZNE/NETCOM series products, run the host computer virtual serial port software driver, you can from the original serial port communication, seamless upgrade to Ethernet communication mode.
Figure 1 Virtual serial port technology
2.2 Security Mechanism
In situations where the security of data transmission is considered, such as ATMs, POS machines, etc., users often hope that the communication equipment itself provides a security mechanism at the bottom, and the risk of attacks and data theft on the network is often more serious than that on the traditional network. Therefore, serial Ethernet conversion equipment needs to establish a firewall mechanism to provide protection for data transmission.
ZNE/NETCOM provides an advanced security mechanism to prevent unauthorized access, provide firewall IP address filtering, and set a maximum of eight authentication IP addresses or IP segments to effectively ensure network security.
In addition, NETCOM equipment also provides AES data encryption technology with 256-bit key according to application needs, adding an unhackable security lock for communication.
Figure 2 Network security
2.3 Internet Explorer Configuration and Monitoring
The device upgraded from the serial port to the Ethernet naturally needs to be locally accessed from the serial port and easily accessed from the network. The easiest way is to directly access, configure and monitor through Internet Explorer without installing any software, and the mobility is very high.
Access, configuration, and monitoring include the management of the conversion device, as well as the management of the serial device itself.
Figure 3 Web server
Serial Ethernet conversion module ZNE built-in Web server, and provide JAVA library and 1.3M Web file download space, users can write their own web pages, serial data, GPIO, ADC and other real-time monitoring, support multiple web browsers access at the same time.
2.4 Domain Name Resolution
If the serial device is connected to the network through the ADSL Modem, its public IP address is dynamically assigned by the network service provider, and the communication in the network must be IP to IP. In order to solve this problem, the domain name mechanism is used on the network to achieve dynamic IP search. Therefore, the serial device must work normally in this environment. Support for domain name resolution (DNS) is required.
ZNE/NETCOM devices support the DNS protocol and can obtain the dynamic IP address of the server through domain name resolution, greatly enhancing the flexibility of network access.
ZNE/NETCOM does not even need to specify an IP address; the internally implemented DHCP protocol can automatically obtain the IP address from the route.
Figure 4 DNS domain name resolution
2.5 Network Performance Optimization
The monitoring equipment connected to the network does not need network communication all the time, so that the device has the function of automatically disconnecting the network connection when it does not communicate, which will undoubtedly bring huge resource savings to the device and the network, and also reduce the occupation of network traffic.
ZNE/NETCOM can not only find the idle state of system communication through setting, but also detect the connectivity status of the network and detect whether the monitoring party is online. In various cases without connectivity, ZNE/NETCOM will disconnect the TCP connection.