OPC UA 1 Client 2 Servers Loopback

OPC UA is an Ethernet communication protocol based on a client-server architecture. This example demonstrates the communication between one OPC UA Client and two OPC UA Servers.

All three OPC UA stations are in the same system and on the same Ethernet interface. This is achieved by assigning multiple IP addresses to one Ethernet interface. With this setup, the OPC UA Client and Servers are on the same physical Ethernet interface. Both servers provide data that the client can read and write.

Table of Contents

Setup Prerequisites Wiring of Target Machine Ethernet Configuration of the Client and Servers Initialize and Open the Simulink Model Model Description Build, Download, and Run the Example Restore Target Machine Configuration Additional References

Setup

Prerequisites

You will require the following to run this example:

Speedgoat real-time target machine with at least one unused Ethernet interface
"Runtime License File" that includes one OPC UA Client license and two OPC UA Server licenses. Refer to the Runtime Licensing documentation for more information

Wiring of Target Machine

No physical wiring is required.

Ethernet Configuration of the Client and Servers

Use the Speedgoat Ethernet Configuration Tool to assign the IP address to one unused Ethernet interface (on-board or IO71x/IO79x) on the target machine. The communication between the client and the server(s) on the unused Ethernet interface is performed over the localhost. No cable is required.

The IP address assigned should be 192.168.10.1. The netmask for this local address is 255.255.255.0. This IP is used as the gateway address for the client and server(s) in this example.

 
% Configure the Ethernet interface for the OPC UA example
speedgoat.configureEthernet; % Open the Speedgoat Ethernet Configuration tool

Add the IP addresses of the client and server(s) to the same Ethernet interface. Adapt the name of the interface according to your target machine configuration.

 
IP_Client_10 = '192.168.10.10';
IP_Server_20 = '192.168.10.20';
IP_Server_21 = '192.168.10.21';
 
InterfaceName = 'ETH1'; % Ethernet Interface on the target machine used for this example. Adapt this according to your machine.
ipAliasObj = speedgoat.IpAliasConfiguration();
ipAliasObj.add(InterfaceName, {IP_Client_10, IP_Server_20, IP_Server_21});

Check the server Ethernet settings:

ipAliasObj.show();

Initialize and Open the Simulink Model

 
% Sample time
Ts = 0.001;
 
% Open Simulink model
modelName = 'sgMdl_OPCUA_1Client2Server';
open_system(modelName);

Model Description

The model sets up the communication for the OPC UA Client and the OPC UA Servers. The Station ID, Connection ID and IP address parameters are aligned to achieve a better understanding of signal flow and how the blocks are related. The first server has Station ID 20 and its IP address ends with 20. The client communicates with the server via Connection ID 20. The second server has Station ID 21 and its IP address ends with 21. The client communicates with the server via Connection ID 21. The client has Station ID 10 and its IP address ends with 10. Station ID and Connection ID parameters are not related to the OPC UA protocol. Instead, they just serve to link blocks in the Simulink model.

Every 10 milliseconds, the client writes data to the first server and reads data from the second server. The data is structured as follows:

Constant signal of type int8
Counter signal of type int16
Sine wave of type double
Pulse signal of type single

The model illustrates how a server's data can be organized in a tree with the help of the Node Identifier and the Parent Identifier parameters. You can use an external client tool to parallelly connect to the servers, view the tree and monitor the signals. The UA Expert is a common tool for that purpose.

Build, Download, and Run the Example

To run the example, either run the following code section or click the Run on Target button in the REAL-TIME tab in the Simulink model.

 
% Build the Simulink model
slbuild(modelName); % this will create the real-time application file (.mldatx)
 
% Create and connect to the Speedgoat real-time target machine
tg = slrealtime;
tg.connect;
 
% Download the real-time application to the target machine
tg.load(modelName);
 
% Set the stop time
tg.setStopTime(30);     % seconds
 
% Prepare the Simulink Data Inspector to plot signals
Simulink.sdi.clearAllSubPlots;
Simulink.sdi.setSubPlotLayout(1,1);
Simulink.sdi.view;
 
% Start the real-time application
tg.start;
 
% Select the signals for plotting, set the axis limits and line colors
sdiRunIDs = Simulink.sdi.getAllRunIDs;
sdiLatestRun = Simulink.sdi.Run.getLatest;
sdiSignals = sdiLatestRun.getAllSignals;
for k = 1:8 % Display all signals in the plot
    sdiSignals(k).Checked = 1;
end
pause(1)
Simulink.sdi.setSubplotLimits(1,1,'AllRange',[0,30,-140,140]);

The output is then visible in the Simulink Data Inspector (SDI). You should see the four signals the first server receives from the client and the four signals the client receives from the second server.

Restore Target Machine Configuration

To restore the default configuration, you can simply reopen the Speedgoat Ethernet Configuration Tool and tick the Show Advanced Settings checkbox. Then click the Restore button in the bottom right.

This will erase the IPs of every Ethernet interface and set the host link IP to 192.168.7.5 and the netmask to 255.255.255.0.

We recommend restoring the default settings to reduce possible configuration errors.

Documentation