Snap7 client

A python based snap7 client for effortless Siemens PLC DataBlock reading and writing.

How? Provide JSON representing the Data Block structure and the tool will handle the rest.

Example run

• Check the example JSON and TIA portal screenshot in the resources directory
• Check the example run in the snap7_manager.py main

note: your DB must use non optimized data access

right click DB, then: Properties > Attributes > uncheck Optimized block access

note: your PLC must permit the PUT/GET requests from extern clients

open PLC properties > Protection & Securrity > Connection Mechanism > check Permit access with PUT/GET...

loaded json:

{
    "var_string": {"datatype": "String", "offset": 0.0},
    "bl5": {"datatype": "Bool", "offset": 256.0},
    "bl4": {"datatype": "Bool", "offset": 256.1},
    "bl3": {"datatype": "Bool", "offset": 256.2},
    "bl2": {"datatype": "Bool", "offset": 256.3},
    "bl1": {"datatype": "Bool", "offset": 256.4},
    "var_bool": {"datatype": "Bool", "offset": 256.5},
    "byte_arr": {"datatype": "Array[0..1] of Byte", "offset": 258.0},
    "var_struct": {
        "datatype": "Struct",
        "offset": 260.0,
        "children": {
            "var_struct_string": {"datatype": "String", "offset": 260.0},
            "var_struct_bool": {"datatype": "Bool", "offset": 516.0},
        },
    },
}

read data:

 {
    "var_string": "",
    "bl5": False,
    "bl4": False,
    "bl3": False,
    "bl2": False,
    "bl1": False,
    "var_bool": True,
    "byte_arr": None,
    "var_struct": {"var_struct_string": "", "var_struct_bool": False},
}

Automatic JSON generator

If you dont wanna write the whole json by yourself, use XMLDataBlockReader:

Generate XML

1. in TIA portal go: Version Control Interface > Add new workspace > Workspace_1
2. Configure the workspace and drag and drop items (or whole configuration to the workspace)
3. Export changes to workspace (icon) > Synchronize (icon)
4. TADAAA! you have an XML

Generate JSON

1. run the utils/xml_datablock_reader.py with provided XML file path:

   python xml_datablock_reader.py <input_file_path.xml> <output_file_path.json>

2. TADAAA! you have the JSON!

3. fill the offset values (including the decimal part) so they are not None anymore