Connect an OPC UA client to read, write and use methods from a server.¶

Prerequisites¶

Modules

External Ressource

An OPC UA Server

Checkout branches

git checkout origin/osp-alarms-web-configuration .
git checkout origin/osp-opc-ua-configuration .
git checkout origin/osp-variables-configuration .

In general be sure to have a correctly configured OPC UA server that will accept your connection using the certificates correctly. Also don’t forget to add the certificates inside the certs/external directory.

Objectives¶

How to read a value on your OPC UA Server
How to write a value on your OPC UA Server
How to use a method on your OPC UA Server

Description¶

In this tutorial, you will learn how to create an OPC UA client and use it with your OPC UA server. You will only need an OPC UA server to connect to.

Configuration structure¶

Steps¶

Note

The complete example can be checkout using

git checkout origin/example-opc-ua-read-write-methods-using-various-parameters .

Note

If you decided to checkout the origin/example-opc-ua-read-write-methods-using-various-parameters branch, do not forget to replace the IP used in configuration files with your own stack’s IP.

Warning

The setup of the certificates can take some time and be tiresome but is mandatory for any OPC UA production server. Your server certificate have to be placed in the certs/external directory. Of course the server has to accept the certificates of our module and OnSphere.

1. Create the dashboard to visualize the values¶

Create a dashboard with a widget where you can subscribe to values.

root/dashboard/dashboard.view

{
  "configuration": [
    {
      "type": "ValueSubscription",
      "id": "vdwEzlGo",
      "title": "test",
      "valueSubscriptions": {
        "values": [
          {
            "id": "root.opc-ua.device",
            "type": "BOOLEAN",
            "right": "READ"
          },
          {
            "id": "root.opc-ua.boolean-value",
            "type": "BOOLEAN",
            "right": "READ"
          }
        ]
      }
    },
    {
      "valueSubscriptions": {
        "values": [{"id": "root.opc-ua.callback-1","right": "READ_WRITE"}]
      },
      "basicWidgetSettings": {
        "showLabel": true,
        "showTooltip": true,
        "showIcon": true,
        "showValue": true
      },
      "id": "YNu7-D8O",
      "type": "BasicInputOutputValue",
      "title": "testes"
    }
  ],
  "layout": {
    "lg": [
      {
        "w": 5,
        "h": 7,
        "x": 1,
        "y": 0,
        "i": "vdwEzlGo"
      },
      {
        "w": 4,
        "h": 2,
        "x": 7,
        "y": 0,
        "i": "YNu7-D8O"
      }
    ]
  },
  "breakpoints": {
    "lg": 1200,
    "md": 996,
    "sm": 768,
    "xs": 480,
    "xxs": 0
  },
  "cols": {
    "lg": 12,
    "md": 10,
    "sm": 6,
    "xs": 4,
    "xxs": 2
  }
}

root/dashboard/dashboard.web

{
    "moduleId": "modules.web.web-1",
    "title": "Home",
    "description": "OnSphere home",
    "tags": []
}

2. Create different OPC-UA elements¶

The device :

root/opc-ua/device/device.opc-ua

Note

If you decided to checkout the origin/example-opc-ua-read-write-methods-using-various-parameters branch, do not forget to configure the information relatives to your server (the IP, port, folder and Nodes). If you want to use this as such you can refer to the following github project and use the server example https://github.com/Azure-Samples/iot-edge-opc-plc

{
    "moduleId": "modules.opc-ua.opc-ua-1",
    "ipAddress": "todoreplace",
    "port": 50000,
    "authenticationMethod": {
        "type": "UsernamePassword",
        "passwordProvider": {
            "password": "demo",
            "type": "PLAINTEXT"
        },
        "username": "sysadmin"
    }
}

root/opc-ua/device/value.ospp

{
    "name": "Device status",
    "description": "",
    "type": "BOOLEAN"
}

The two outputs, the first one using a method and the second one using a standard write :

root/opc-ua/method-output/output.opc-ua

{
    "linkedDevice": "root.opc-ua.device",
    "methodIdentifier": "ResetStepUp",
    "methodObjectIdentifier": "Methods",
    "namespaceIndex": 3,
    "type": "Method"
}

root/opc-ua/write-output/output.opc-ua

{
    "type": "Write",
    "linkedDevice": "root.opc-ua.device",
    "namespaceIndex": 3,
    "nodeIdentifier": "SlowUInt1"
}

Different values, representing a Node of different type that we will read every seconds :

root/opc-ua/int-value/owner.opc-ua

{
    "type": "DirectRead",
    "linkedDevice": "root.opc-ua.device",
    "namespaceIndex": 3,
    "nodeIdentifier": "SlowUInt1",
    "pollingFrequency": {
        "value": 1,
        "unit": "SECONDS"
    }
}

root/opc-ua/int-value/value.ospp

{
    "name": "Test value DirectRead",
    "description": "",
    "type": "INTEGER"
}

Creation of a OPC UA subscription on a boolean value that we read :

root/opc-ua/boolean-subscribe/owner.opc-ua

{
    "type": "Subscription",
    "linkedDevice": "root.opc-ua.device",
    "namespaceIndex": 3,
    "nodeIdentifier": "AlternatingBoolean",
    "samplingInterval": {
        "value": 1,
        "unit": "SECONDS"
    }
}

root/opc-ua/boolean-subscribe/value.ospp

{
    "name": "Test value DirectRead",
    "description": "",
    "type": "BOOLEAN"
}

3. Write variables that can handle outputs¶

Here is an example of a callback using a variable to call an output (the corresponding output is defined below) :

root/opc-ua/callback-1/callback.ospp

{
    "linkedOutputs": [
        {
            "outputId": "root.opc-ua.method-output"
        }
    ]
}

root/opc-ua/callback-1/owner.variables

{
    "moduleId": "modules.variables.variables-1"
}

root/opc-ua/callback-1/value.ospp

{
    "name": "Test val",
    "description": "",
    "type": "BOOLEAN"
}

4. Result of the example¶

Connect to the frontend and go to the dashboard corresponding to the above configuration. There you can use the search field to subscribe to a value.

../../_images/example_opc_ua_front_end.gif

Warning

Be aware that you have to correctly configure the certificates (if in use) to be able to connect and subscribe to the values.