Beckhoff TwinCAT Connector
Overview
The Beckhoff TwinCAT connector provides tag-based read and write access to a Beckhoff PLC over ADS, using the TwinCAT.Ads SDK.
Every poll cycle reads each subscribed In/InOut tag via ReadAny against a variable handle created once at connect time; Out/InOut tag writes go out immediately via WriteAny as soon as a tag's value changes.
The connector detects when the underlying ADS connection is lost and reconnects automatically without blocking the read cycle - reconnection runs on its own dedicated background thread, and the previous AdsClient is properly disposed before a new one replaces it.
Parameters
| Name | Values | Description |
|---|---|---|
| Type | BECKHOFFTWINCAT | The connector type identifier. |
| NETID | AMS Net ID, e.g. 192.168.0.2.1.1 | The target PLC's AMS Net ID. |
| IP | IP address | The target PLC's IP address. |
| PORT | integer | The ADS port for the target PLC runtime. Defaults to 851 (the first PLC runtime system on a device; 852 for the second, and so on). |
| UpdateRate | milliseconds (integer) | How often the connector polls all subscribed tags. Defaults to 1000. |
| ReconnectDelay | milliseconds (integer) | Delay between reconnect attempts while the PLC is unreachable. Defaults to 5000. |
Supported Tag Types:
| Tag Type | Address | Behaviour |
|---|---|---|
| Any standard tag | The full ADS variable path, e.g. MAIN.bStart or GVL.rTemperature | Read every cycle (In/InOut). Out/InOut tags are written back to the PLC whenever their value changes. |
The tag's own DataType (Int/Decimal/Bool/String/Object) determines the .NET type used for the underlying ReadAny/WriteAny call - a tag with an unrecognised DataType is skipped with a %DEBUG notice rather than attempted.
Connector Methods
None currently implemented - all read/write access goes through tag polling and ChangeData writes rather than on-demand commands.
Addressing
The Address field of a tag is the ADS variable's full path as it appears in the PLC project. A variable handle for each address is created once, at connect time - a variable that doesn't exist on the PLC (or a typo'd path) is reported via %DEBUG during connection setup rather than on every subsequent read.