CodesysJSONFile

Read JSON file to CODESYS Structs

Uses the PRO JSON lib by TVM, version 1.0.0.16

Usage

Some customization of FB required:

For each JSON object you should provide two types of structs:

• Your normal DUT (YOUR_STRUCT, YOUR_SUB_STRUCT in example)
• JSONVAR DUTs (note! names should match JSON file exactly) (JS_YOUR_STRUCT, JS_YOUR_SUB_STRUCT in example)

That should be done for every JSON object type. Core:

And inner:

And converting methods

• For top-most JSON object (CORE_JS_TO_ST in example)
• And for inner JSON objects (SUB_JS_TO_ST in example)

Also you should specify your DUTs in function block and maximum possible array size of the topmost object (see Limitations/Arrays )

Limitations

Memory

Well, it's memory-consuming. The memory usage is specified by changing constants at GPL_JSON list in PRO_JSON library section.

Naming

The names in JSON and in ST-based JSONVARs should match exactly. For JSON fields of

{"field":"value",
 "otherField":3.14
}

ST-struct should be:

TYPE JSONST
STRUCT
	field  :  		JSONVAR;
	otherField:		JSONVAR;
END_STRUCT
END_TYPE

Arrays

The Array could not be topmost structure:

[
{"obj": "value"},
{"obj": "value"}
]

This is NOT valid.

The topmost array should be named:

{"myArr":
[
{"obj": "value"},
{"obj": "value"}
]}

The corresponging ST structure is

TYPE JSONST
STRUCT
	obj  :  		JSONVAR;
END_STRUCT
END_TYPE

And the name of the array in the ST code should match the JSON exactly:

VAR
  myArr: ARRAY[1..10] OF JSONST;
END_VAR

UTF8

Do not work with non-english UTF8 symbols (or I failed to do this).

Application name

Application name should match to specified in GPL_JSON list in PRO_JSON library section ('Application' by default)

Requirements:

For Cyryllic symols use Win-1251 (CP1251) encoding. Use Owen String Utils to deal with CP1251->WStrings

Use iconv from Linux to convert file encoding if needed.