Considering the advantages of modern computer communication technologies, especially Ethernet, it is in place to ask how to utilize them in an industrial system (by the industrial system we can understand a control system, PLC, smart controller or measurement instrument). When building a new system, the answer is evident, simply to buy one with already implemented Ethernet interface.

    However, in case of already installed system (or when the manufacturer doesn’t offer an Ethernet variant) it is necessary to utilize some alternative solution. When looking for such solution it is desirable at first to ask, what effect should the Ethernet bring to the user? Then according to the desired effect it is possible to choose a proper solution. Basically, the expected effect is to get a remote access to the system, either over local intranet or over Internet.

    When examining existing industrial systems one can find that the common feature of majority of the systems is presence of some kind of serial interface (RS- 232/ 422/ 485), regardless of the used communication protocol. Considering this, the obvious way of connecting any already installed industrial system to the local network is to use some kind of Serial/Ethernet converter/gateway. Functionality of such gateway can vary according to the user’s needs; from simple bridge to sophisticated embedded web sever.

Fig .1

    The application of the S/E gateway assumes that the connected system is already equipped with a serial communication port and there is some software utilizing the communication link. The S/E gateway guarantees the transfer of data between PC and the remote device over Ethernet. The simplest way is to use only bridge, which tunnels the serial protocol of the industrial system over intranet or Internet, with dedicated gateways on both sides of the communication link. Such approach is suitable for interconnection of two non-PC devices.

    However, when connecting a system to PC, this solution has some substantial drawbacks. In fact, it is cumbersome to convert the data from Ethernet back to the serial line, since it is much more simple to equip the computer with a standard network card. The gateway on the PC side is replaced by software, which simulates operations of a standard COM port (see Figure 1.). There is no need to change the user software; the user only selects the virtual COM port in the configuration of his software. There is no need for dedicated hardware also, so there is no limitation on the number of computers, which can be connected to the system. The only limitation is that there can be only one computer currently connected to the remote system.

   Hardware of the gateway is based on module ATC-2000 or ATC-1000, developed by ATC.This module integrates an advanced microprocessor standard Ethernet controller. These modules are the appropriate balance in the price / performance ratio. Board with a power source 9V - 24V, small EEPROM to store configuration, RS-232, RS-485 and RS-422 drivers