Reading OPC UA Data with ControlCom Edge Server

An OPC UA client connects the Edge Server to an OPC UA server (Kepware, Ignition, Siemens, B&R, or any other compliant server) and reads selected nodes into platform variables. You configure it from the platform in the device's SDK Configuration editor; the Edge Server picks the configuration up on its next restart.

Prerequisites

The Edge Server must already be onboarded as a ControlCom Gateway. The Edge Server getting started guide covers deployment and onboarding.

Each node you read needs a variable on the gateway to receive it. Create those first (see Creating a Variable); you select each variable by its Topic Property Path when you add an item below. The item editor also has a Create New Variable button if you prefer to create them as you go.

Creating an OPC UA Client

1. Open Devices under System in the sidebar and select the onboarded gateway.
2. Open the Edge Server tab. The SDK Configuration editor opens on its Clients tab.
3. Click Add Client and choose OPC UA in the Add New Client dialog.

The new client opens in a side panel and also appears as a card on the Clients tab; click the card to reopen it later. New clients start disabled.

The client panel has three tabs: Connection, Settings and Items.

Connection

1. Enter a Client Name.
2. Enter the OPC Endpoint URL of the server, for example 192.168.1.100:4840 or opc.tcp://192.168.1.100:4840. The default OPC UA port is 4840.
3. Turn on Enable Client.

Settings

The Settings tab holds maintenance actions: Remove Client deletes the client from this configuration, Export Variables downloads the item list as a CSV for bulk editing, and Import Variables loads an item list from a CSV.

Items

An item is one node read from the server. Click Add Item, then select the new entry in the list on the left.

On the General tab:

1. Enter the Node ID of the node to read, for example ns=2;s=Temperature or ns=3;i=1001.
2. Enter the Attribute ID. It defaults to 13, the node's Value attribute, which is what you want in nearly every case. Other attributes are 1 (NodeId), 2 (NodeClass) and 3 (BrowseName).
3. Select the Topic Property Path, which is the variable that receives the value. The item's data type (number, boolean or string) follows the selected variable.
4. Optionally select a Write Variable to let the platform write to this node when a matching command is sent. The default is No Write Allowed.

On the Scaling tab (number items only), Scale (defaults to 1) multiplies the raw value, Offset (defaults to 0) is added after scaling, and Decimals (defaults to 2) rounds the result. If the server reports 857 and the real value is 8.57, set Scale to 0.01.

On the Misc tab, Send if Stale After (ms) forces a publish when the value has not changed in that time (defaults to 10000, ten seconds), and Deadband Percentage (defaults to 5, number items only) suppresses changes smaller than that share of the previous value.

On the Transforms tab you can add Value Transforms that rewrite the value before it is published.

Saving

Click Save Configuration in the editor header, then confirm with Save Configuration in the Save SDK configuration? dialog. The configuration is stored on the platform; the gateway applies it on its next restart.

Deployment

The Edge Server reads its configuration when it starts, so a restart is what puts the new client into service. There are two ways to trigger one.

From the platform, open the gateway's Details tab and click Restart in the Send command panel. The Edge Server restarts and reconnects with the new configuration. Edge Server Management describes the full set of SDK commands.

On the gateway itself, restart the container as described in the Edge Server getting started guide.