blark 0.1.6

Beckhoff TwinCAT IEC 61131-3 parsing tools

Beckhoff TwinCAT IEC 61131-3 Lark-based Structured Text Tools

Or for short, blark. B(eckhoff)-lark. It sounded good in my head, at least.

The Grammar

The grammar uses Lark's Earley parser algorithm.

The grammar itself is not perfect. It may not reliably parse your source code or produce useful Python instances just yet.

See issues for further details.

The plan

As a fun side project, blark isn't at the top of my priority list.

Once I get around to it, I hope to:

• Introduce user-friendly Python dataclasses for all PLC constructs
• Create a lark Transformer to take tokenized PLC code and map them onto those dataclasses
• Fix the grammar and improve it as I go
• Maybe create a black-style autoformatter for PLC code

Requirements

• lark-parser
• pytmc (for parsing TwinCAT projects)

How to use it

1. Preferably using non-system Python, set up an environment using, e.g., miniconda:

$ conda create -n blark-env python=3.7
$ conda activate blark-env

2. Install the library (using conda or otherwise, these steps are the same)

$ pip install blark

3. Run the parser. Supported file types include those from TwinCAT3 projects ( .tsproj, .sln, .TcPOU, .TcGVL).

$ blark parse -vvv blark/tests/POUs/F_SetStateParams.TcPOU
start
  iec_source
    function_declaration
      derived_function_name     F_SetStateParams
      bit_string_type_name      BOOL
      input_declarations
        var_input_body
          var_init_decl
            variable_name       nStateRef
            simple_spec_init
              integer_type_name UDINT
...

If you want to use the tokenized source for your own purposes, you'll have to dig into the source code from there.

Acknowledgements

Based on Volker Birk's IEC 61131-3 grammar iec2xml (GitHub fork here) and A Syntactic Specification for the Programming Languages of theIEC 61131-3 Standard by Flor Narciso et al.