LabVIEW TwinCAT ADS

Easy to use Unofficial LabVIEW TwinCAT API for communicating with Beckhoff PLCs via ADS. Features include Invoking Rpc Methods, Reading/Writing of PLC variables (including all Standard types, Pointers, References, Time, Strings, WStrings, Structs composed of the aforementioned, Nested STRUCTs and Multi-dimensional Arrays of the aforementioned datatypes), introspective capabilities (get the symbol and type information), the ability to build your own low-level VIs via Extensions and more.

Minimum Requirements

• LabVIEW 2018 (32/64 bit) and above
• .NET Framework 4.6.2 (installed by default with LabVIEW)
• TwinCAT 3.1.4024.10 and above (haven't tested below 4024.10 might work with lower versions)

Changelog

Fixes:

• Fixed failure in application build due to Flatten .NET Symbol Information.vi

Showcase

VIs included in the API:

Examples

Invoke Method:

Event-Driven Reading:

Write Symbol:

Read Symbol:

Pointer Support:

High-Speed Reading:

Developer Notes

Connection

1. You may notice that the Connect.vi is slow in connection. This is normal. The VI is simply caching the symbols and types in LabVIEW rather than keeping them in a .NET collection. The reason for this is that lookup times on the .NET Ads-XYZ-Collection are very slow. The further I moved away from making calls to any of Beckhoff's .NET libraries the faster operations became. The penalty for doing this is a slow connection.

2. Because of the caching system, online changes are currently not supported.

3. You do not need to disconnect before disposal. Dispose.vi VI will disconnect for you.

Read, Write and Invoke Method

1. Operations involving UNIONs types are not yet supported.

2. To read and write to pointers simply add the dereferencing symbol to your symbol name e.g. pValue^.

3. First calls to an operation (Reading/Writing a symbol or Invoking a Method) will be slow.

   Typical first call times for my RYZEN 3600X system with 1 isolated core are ~5ms for ARRAY[0..999] OF LREAL and ~40ms for ARRAY[0..999] OF ST_STRUCT where ST_STRUCT is:

   TYPE ST_STRUCT :
   STRUCT
       bVar  : BOOL;
       dtVar : DT;
       fVar  : LREAL;
   END_STRUCT
   END_TYPE

   Subsequent calls resulted in read/write/method invoking times of 1-2ms for ARRAY[0..999] OF LREAL and ~20ms for ARRAY[0..999] OF ST_STRUCT. The task cycle time was 1ms.

4. When sending numbers, arrays of numbers or structs with numbers, enums, etc. The numbers will be coerced to the type defined in the PLC for that variable/parameter. This is by design. LabVIEW is a graphical language so switching between Single Precision Float and Doubles is an absolute pain. There are no aliases in LabVIEW.

5. LabVIEW Arrays don't need to be the same size as the PLC arrays to write them. Write what you need, the rest will be filled in with defaults.

Events

1. Online change is not supported. However, you can update variables on the PLC without needing to disconnect on the LabVIEW side via Login with Download, Restart TwinCAT System and Activate TwinCAT Configuration. All symbols will automatically be reloaded into memory.

   NOTE: Any reads or writes running during this process will produce errors, just ignore these errors until reconnection is complete. They will stop once that happens.

2. Don't forget to close the Registration Refnum after you're done. User Events references are automatically closed on disposal.

Other

1. When using extensions. Please only close the .NET references with an asterisk (*) on their label at the connector pane. The ones without an * are managed for you.

Please feel free to contribute to the project or report bugs

---