How to Transfer Data from MQTT to OPC DA

Open Automation Software can be used to transfer data from a MQTT broker to an OPC DA device locally or over a network. This guide walks you through downloading and installing OAS, configuring a MQTT connector and creating a data source tag and an OPC DA tag.

This guide uses the Data Route feature of OAS to transfer a Tag's value to another Tag's value using the Tag-to-Tag method.

For this guide on how to transfer data from a MQTT broker to an OPC DA device you will need:

• To install MQTT Explorer or a similar tool for publishing messages to a MQTT broker and subscribing to messages in a MQTT broker

ℹ️ For simulation purposes, you will use the OPC server available in the OAS platform to write a Tag value. If you already have an OPC server or device available, you can also adjust your configuration to suit your own OPC server or device.

1 - Download and Install OAS

If you have not already done so, you will need to download and install the OAS platform.

Fully functional trial versions of the software are available for Windows, Windows IoT Core, Linux, Raspberry Pi and Docker on our downloads page.

On Windows, run the downloaded setup.exe file to install the Open Automation Software platform. For a default installation, Agree to the End User License Agreement and then click the Next button on each of the installation steps until it has completed.

If you'd like to customize your installation or learn more, use the following instructions:

• Windows Installation
• Linux Installation
• Raspberry Pi Installation
• Docker Installation

The OAS Service Control application will appear when the installation finishes on Windows.

Click on each START SERVICE button to start each of the three OAS services.

2 - Configure OAS

Web Configuration Application

Configuration of the OAS server is performed from the built-in Web Configuration Application. This is the main application for accessing any settings within the OAS server and is completely self-contained within the server.

You can reach this by opening your browser to:

http://<your server>:58725/app/config

If you are browsing from the OAS machine itself, you can use localhost, otherwise use the IP address of the machine. You will also need to ensure port 58725 is open on both the client and the server or you may not be able to reach the application.

On a new installation the OAS engine has no accounts yet, so the first screen you see is Create Admin Account. Once the administrator account exists that screen is not shown again, and browsing to the application displays the sign in screen instead.

1. Enter a name for the administrator in the Admin user name field. Typically you would use admin, but you can use whatever name you choose.

2. Enter a password in the Password field, then enter the same password again in the Confirm password field.

3. Click on the Create admin & sign in button. The account is created and you are signed in to the engine.

To sign in from then on, enter the Network node of the OAS engine, then the Username and Password of your account, and click on the Sign in button.

Legacy Configuration Application

1. From your operating system start menu, open the Configure OAS application.

2. Select the Configure > Tags screen.

   Important

   If this is the first time you have installed OAS, the AdminCreate utility will run when you select a screen in the Configure menu. This will ask you to create a username and password for the admin user. This user will have full permissions in the OAS platform.

   For further information see Getting Started - Security.

3. If this is the first time you are logging in, you will see the AdminCreate utility. Follow the prompts to set up your admin account. Otherwise, select the Log In menu button and provide the Network Node, username and password.

   

   

3 - Create Security Group and User

When connecting to the local OAS OPC UA server, you need to configure a security group and a user to provide Tag read/write access. You'll need these credentials when creating the OPC UA connector instance later.

ℹ️ You can skip this step if you are connecting to your own third party OPC UA server.

1. Select Security in the sidebar.

2. Click + Add, enter a Name such as OPC UA Access and click Create. Once created, the security group name should appear in the list of security groups.

   

3. In the Tags section, ensure Get Tag Group Names and Get Tag Names are turned on. This setting is required when browsing the OPC UA server tag structure once you get to the step of assigning the OPC UA data source to a Tag.

   

4. In the Read Tags section, ensure Disable All Tags From Reading is turned off.

   

5. In the Write Tags section, ensure Disable All Tags From Writing is turned off.

   

6. Select Users in the sidebar.

7. Click + Add, enter a User name such as opcuauser, set a Password, set the Security group to OPC UA Access and click Create. Once created, the user name should appear in the list of users.

   

4 - Configure MQTT Data Source Connector

In the following steps you will create and configure a MQTT Connector to connect to a third party broker so that tags will be able to subscribe to a topic. For the purposes of this guide, you will connect to the public HiveMQ broker.

1. Select Drivers in the sidebar.

2. Click + Add, enter a meaningful Driver Interface Name to give this driver interface instance a unique name, and click Create. Once created, the driver interface name should appear in the list of drivers.

3. Ensure the following parameters are configured:

   • Driver: MQTT
   • IP Address: broker.hivemq.com
   • Port: 1883
   • Client ID: OAS_Client_123

   

   The app flags the empty User Name and Password fields. The public HiveMQ broker accepts anonymous connections, so leave them blank here. Fill them in if the broker you are connecting to requires authentication.

   Tips

   If you are having trouble reading a value in later steps, try to change the Client ID to something else as each client ID connecting to the broker must be unique.

4. Turn on Enable and click on the Apply changes button. The driver interface is not active until it is enabled and the changes are applied.

   

5 - Add Tags

In this step you will add two tags. One tag to represent a JSON payload coming from an external data source and a second Tag to represent the sensor value.

1. Select Tags in the sidebar.

2. If you want to add a Tag at the root of the tag list, make sure no Tag Group is selected and click on the + button, then choose Add tag.

   

   If you want to add a Tag to a Tag Group, select the Tag Group first and then click on the + button and choose Add tag here.

   You can also add Tag Groups by choosing Add group.

3. Enter TemperatureSensorJSON as the Tag name and click the Create button.

   

4. Repeat the above two steps and add another Tag with the name TemperatureSensor.

   

6 - Assign MQTT as Tag Data Source

You will now set the Tag's data source to the MQTT driver interface that you created previously.

At the end of this section you will need to use a tool like MQTT Explorer to publish a value to your Tag.

1. Select the Tag that will source data from the MQTT data source.

   

2. Set the following properties:

   • Data Type: JSON
   • Data Source: MQTT
   • Select Driver Interface: MQTT Data Source
   • Topic: oas/temperature

   

3. Click on the Apply changes button to apply the changes.

4. Using an MQTT testing tool to publish messages, such as MQTT Explorer, publish a JSON message to the oas/temperature topic.

   {
       "temperature": 24.9
   }
   

   

   

   

5. Check that the quality status is Good and you can see the JSON value.

   

7 - Parse JSON Payload

In this step you will extract the sensor value from the JSON payload using a Calculation Tag and JSON functions.

1. Select the Tag that will represent the temperature value.

   

2. Set the Data Source value to Calculation.

3. Next to the Calculation field click on the Edit… button.

4. In the Edit Calculation window enter the following function.

   JSONQUERY([TemperatureSensorJSON.Value], "$.temperature")
   

   This will extract the temperature field from the TemperatureSensorJSON Tag value.

   Click the OK button to save the calculation.

   

5. Click on the Apply changes button to apply the changes.

6. You should now see the sensor value displayed for the Tag.

8 - Add Simulated OPC DA Tag for Temperature Input

In this section you will create a Tag to represent a Temperature input in a destination OPC DA device. This Tag is used for simulation because we are using the OAS OPC server.

ℹ️ If you have your own third-party OPC server where you can simulate a Tag value then you can skip this step.

1. Select Tags in the sidebar.

2. Make sure no Tag Group is selected and click on the + button, then choose Add tag.

   

3. Provide a Tag Name such as OPCDA_TemperatureInput and click the Create button.

   

This tag will have a default value of zero. It will automatically update once your destination data connector and tag are configured.

9 - Assign OPC DA as Tag Data Destination

You will now set the Tag's data destination to an OPC destination and configure the OPC Item to point to one of the OAS tags we created for simulation.

ℹ️ If you already have your own OPC data destination, you can browse your own data source in Step 3.

1. Select the Tag that will output data to your OPC destination tag.

   

2. Set the Data Source to OPC.

3. Click on the Browse… button next to the OPC Item field. In the Browse for OPC Item window, set the OPC DA Server to OPCSystems.NET, then select Local in the Branches list. In the OPC Items list select OPCDA_TemperatureInput.Value. You should see the OPC Item is now OPCSystems.NET\Local.OPCDA_TemperatureInput.Value.

   Click on the Use this item button to select this OPC item.

   

4. Click on the Apply changes button to apply the changes.

   

10 - Configure Tag-To-Tag Data Route

In this section you will configure the Target of the source Tag to be the destination Tag value. This means whenever the source Tag value is updated, the destination Tag value will also be updated. This will cause a write operation on any associated driver if it is supported.

1. Select the source data Tag.

   

2. Scroll down to the Target section.

   

3. Enable the Enable Write to Target option.

   

4. Click on the Browse… button, select the destination Tag and click on the Use this tag button.

   

5. Optionally, configure the Deadband property or enable Write Continuously to configure a continuous writing frequency.

   

6. Click on the Apply changes button to apply the configuration.

7. To verify that your data transfer is working correctly, select the destination Tag and check that the Tag value matches the Tag value of the source Tag.

   

   You should also verify that the Tag value has been written to your destination device. Depending on your configuration in step 5 above, this destination value should be updated whenever the source value changes or at the given frequency.

11 - Save Changes

Once you have successfully configured your OAS instances, make sure you save your configuration.

On each configuration page that has a Save button, click on it.

If this is the first time you are saving the configuration, or if you are changing the name of the configuration file, OAS will ask you if you want to change the default configuration file.

If you select Yes then OAS will make this configuration file the default and if the OAS service is restarted then this file will be loaded on start-up.

If you select No then OAS will still save your configuration file, but it will not be the default file that is loaded on start-up.