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Tutorial: Serial Device Networking |
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Using Ethernet Encapsulation to connect to serial devices.
The requirement to move from legacy manufacturing systems to improved systems where data can be analysed at a central location is becoming more viable as costs and manpower decrease.
Ethernet infrastructure is usually in existence, or can be easily implemented. Buildings tend to have existing Ethernet networks. PLC manufacturers are starting to develop Ethernet add-ons to network their PLCs, although you tend to pay a premium for this functionality.
The most cost-effective solution is to use serial device servers (like the Multenet PocketPAD and EtherPAD ranges) to convert serial data to Ethernet data. The cost of laying serial cables over long distances can prove very expensive. Even your legacy software applications can be fooled into thinking it is using a serial port on your workstation by using a Virtual COM Port Redirector like Multenet's Serial Anywhere. A transparent serial tunnel is created over Ethernet. This all happens without changing much of the existing setup. You also do not need to spend lots on upgrading your PLCs with network add-on modules.
What is Ethernet Encapsulation?
Ethernet Encapsulation provides a virtual serial port on your workstation. Use existing serial drivers in the OPC server to communicate to your networked PLCs as if they were connected directly to your workstation. Multenet products, like the PocketPAD or EtherPAD, provide the Ethernet connection for your PLC through which the OPC server sends data.
You can now connect all your serial devices to the network, with the OPC server collecting data to a central server without running extra 3rd party Virtual COM Port Redirector applications.
Ethernet Encapsulation
Ethernet Encapsulation is the enhanced ability of the TOP Server serial drivers to communicate directly with terminal servers like the PocketPAD. TOP Server has integrated Ethernet Encapsulation into the serial drivers used to create an efficient communication tunnel.
If you are familiar with Software Toolbox serial drivers you can select a serial port number from 1 to 16 when configuring a channel. For drivers supporting Ethernet Encapsulation you will now find that you also have the option of selecting "Ethernet Encapsulation" mode, in addition to the com port selection of 1 to 16. The following dialog demonstrates how this selection is presented.
With Ethernet Encapsulation selected, you need to specify an IP address, a port number, and the Ethernet communications format to be used to complete the configuration. This is done when you add a new device to your channel.
When a new device is added to the channel the following device dialog for Ethernet Encapsulation appears allowing you to configure an Ethernet IP address, an Ethernet Port number, and the Ethernet protocol to be used.
This dialog appears on the properties of each device you add to a channel in Ethernet Encapsulated mode. Since this dialog appears for each device, you can have hundreds of serial devices connected to your Ethernet network via serial device servers like the PocketPAD or EtherPAD.
Important Note: When you select Ethernet Encapsulation mode you will notice that the serial port settings such as baud rate, data bits, and parity become greyed out. This occurs because these settings will not be used in Ethernet Encapsulation mode. The terminal server you are using must however have its serial port properly configured to match the requirements of the serial device you plan to attach to the terminal server.
Configuring the Multenet PocketPAD
1. Launch EtherPAD Explorer from the CD. Scan to automatically find Multenet devices attached to your network (local segment).
2. Configure the IP Address and Subnet Mask using "Set IP Address" button. Click "Web configuration" to configure the serial device server. Log into the configuration menu with the default user name "root" and the default password "xxx".
3. Click on "Networking". This will bring up the Network Configuration screen. Verify that the IP Address and Subnet Mask is correct. Also configure the Gateway IP Address should you connect over the WAN.
4. Configure the serial interfaces. From "Home" select "Serial Applications" and "Change Serial Parameters". The parameters should match those of your serial device.
5. Click "Back" and select "Change" on the default TCP/IP Network Application. Change the "Local TCP Port" to 2101. The "Idle Timeout" defaults to 0 (disabled). We recommend setting the time to 10 seconds. If this parameter is left disabled, it will not allow the PocketPAD to drop the Winsock port in the event of a forced disconnection. This, in turn, will not allow the OPC Server to reconnect. Setting the Idle Timeout to 10 seconds will allow the PocketPAD to disconnect the OPC Server's Winsock port when no data is received, allowing the OPC Server to reconnect.
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