Beckhoff Trigger

The Beckhoff Trigger fires a workflow whenever one of the trigger’s monitored symbols receive a new value on a Beckhoff Automation TwinCAT PLC.

Node Properties

The Beckhoff Trigger’s configuration is broken up across two sections …

Connection Configuration

First, define the properties needed to establish a connection to the Beckhoff PLC.

• Local AMS Net ID: A six-octet address of the local device (running the GEA) in the TwinCAT network. This is usually the IP address assigned to the GEA device plus .1.1.
• Local ADS Port: The port over which the ADS communication protocol of TwinCAT is exposed. Defaults to 37250.
• Target AMS Net ID: A six-octet address of the target ADS device, usually defined on the device itself. Usually it is the IP address of the ADS device plus .1.1.
• Target ADS Port: The target runtime ADS port. Defaults to 851.
• Router Host: The hostname or IP address of the TwinCAT router.
• Router Port: The port over which the TwinCAT router is exposed. Defaults to 48898.
• Cycle Time Interval (ms): The length of time, in milliseconds, to wait between requests to the PLC for the values of the subscribed symbol values. The minimum is 10 milliseconds and the maximum is 3600000 (one hour). Lower numbers lead to quicker firing of workflows on value changes, but can also cause performance issues on the GEA device or the Beckhoff TwinCAT PLC.

Subscriptions

Next specify at least one Symbol Name to monitor for value changes. Whenever a change in one of the provided symbol’s value is detected, the trigger will fire.

Note: If two or more symbol values change within the same cycle time, this will lead to the trigger firing once per changed symbol value.

Payload

The payload will include info on the changed symbol, as well as the new value and the timestamp of the change, in the data field. Symbols with dot characters (.) in their name will be treated as nested objects.

For example, given a monitored symbol name of GVL_Var.TestDint1, the Beckhoff Trigger’s payload would look like the following …

{
  "agentEnvironment": {
    "EXAMPLE": "Environment Variable"
  },
  "agentVersion": "1.49.0",
  "applicationId": "555555555555eeeeeeeeeeee",
  "applicationName": "My Great Application",
  "data": {
    "GVL_Var": {
      "TestDint1": {
        "value": 528,
        "timestamp": "2024-09-27T19:17:38.301Z",
        "symbol": {
          "name": "GVL_Var.TestDint1",
          "comment": "",
          "type": "DINT",
          "size": 4,
          "indexOffset": 384808,
          "indexGroup": 16448
        }
      }
    }
  },
  "device": {
    "applicationId": "555555555555eeeeeeeeeeee",
    "attributes": {
      "exampleNumber": {
        "attributeTags": {
          "attrTagKey": "tagValue1"
        },
        "dataType": "number",
        "name": "exampleNumber"
      },
      "exampleString": {
        "attributeTags": {
          "attrTagKey": "tagValue2"
        },
        "dataType": "string",
        "name": "exampleString"
      }
    },
    "creationDate": "2018-03-16T18:19:03.376Z",
    "deviceClass": "edgeCompute",
    "deviceId": "222222222222bbbbbbbbbbbb",
    "id": "222222222222bbbbbbbbbbbb",
    "name": "My Great Device",
    "tags": {
      "aTagKey": [
        "exampleTagValue"
      ],
      "tagWithMultipleValues": [
        "tagValue",
        "anotherTagValue"
      ]
    }
  },
  "deviceId": "222222222222bbbbbbbbbbbb",
  "deviceName": "My Great Device",
  "deviceTags": {
    "aTagKey": [
      "exampleTagValue"
    ],
    "tagWithMultipleValues": [
      "tagValue",
      "anotherTagValue"
    ]
  },
  "flowId": "333333333333cccccccccccc",
  "flowName": "My Great Workflow",
  "flowVersion": "myFlowVersion",
  "globals": {
    "aJsonGlobal": {
      "key": "value"
    },
    "aNumberGlobal": 42,
    "aStringGlobal": "My value"
  },
  "isConnectedToLosant": true,
  "time": Fri Feb 19 2016 17:26:00 GMT-0500 (EST),
  "triggerId": "<{deviceId}-{randomAlphanumericString}>",
  "triggerType": "beckhoff"
}

Limitations

ADS routers only allow a single connection from a host (i.e. a GEA device), and the Target AMS Net ID is ingrained in the connection configuration. This leads to a few important limitations to consider …

• Across all of its deployed workflows, if the GEA contains Beckhoff Triggers that connect to the same ADS router but different Target AMS Net IDs, only one of the triggers will successfully connect. The other triggers will not open a connection, and information about subscription failures will appear in the container logs.
• Similarly, if the device is running a Beckhoff Trigger and Beckhoff: Read Nodes and/or Beckhoff: Write Nodes that connect to the same ADS router but different Target AMS Net IDs, the Read / Write Nodes will fail and will return an error since the one client connection is being used by the Beckhoff Trigger.

Related Nodes

• Beckhoff: Read Node
• Beckhoff: Write Node