array of struct

[hapetter]

Hi.

I try to implement an array of struct in IEC61131-3 ST language. I use a beckhoff PLC.
The C code look like this:

Struct BDD
{
Unsigned char a1;
Unsigned int a2;
Unsigned int a3;
Unsigned int a4;
}
 
struct BDD BDD_table[4] = {
{'X', 1, 1, 2},
{'a', 0, 100, 0},
{'a', 1, 100, 2},
{'X', 2, 5, 4}
};

So:
How to declare array of struct and fill inn data in array?

Thanks!

Best Regards
Hans Pettersson

 

[hapetter]

I tried this, but its not correct...

PROGRAM StateMachine
VAR
TYPE BDD_Table
STRUCT
N_Type: STRING;
N_Index: INT;
Successor0: INT;
Successor1: INT;
END_STRUCT
END_TYPE

BDD_Table: ARRAY [0..4] OF STRUCT;

END_VAR

I have no idea how to assign data in each struct in array...

Anyone?

 

[JesperMP]

This is how it would look like in Siemens SCL, which should be the same as IEC ST:

TYPE BDD
    STRUCT
        a1 : CHAR ;
        a2 : INT ;
        a3 : INT ;
        a4 : INT ;
    END_STRUCT
END_TYPE
    
DATA_BLOCK BDD_table
    STRUCT
        vals : ARRAY[0..3] OF BDD ; 
    END_STRUCT
BEGIN
    vals[0].a1 := 'X' ;
    vals[0].a2 := 1 ;
    vals[0].a3 := 1 ;
    vals[0].a4 := 2 ;
    vals[1].a1 := 'a' ;
    vals[1].a2 := 0 ;
    vals[1].a3 := 100 ;
    vals[1].a4 := 0 ;
    vals[2].a1 := 'a' ;
    vals[2].a2 := 1 ;
    vals[2].a3 := 100 ;
    vals[2].a4 := 2 ;
    vals[3].a1 := 'X' ;
    vals[3].a2 := 2 ;
    vals[3].a3 := 5 ;
    vals[3].a4 := 4 ;
END_DATA_BLOCK

 

[LadderLogic]

The following code compiles in TwinCAT without errors.

In the "Data Types" section:

TYPE BDD :
STRUCT
 a1: STRING[1];
 a2:UINT;
 a3:UINT;
 a4:UINT;
END_STRUCT
END_TYPE

In the "Global variables" section:

VAR_GLOBAL
 BDD_table: ARRAY[0..3] OF BDD :=  (a1 := 'X', a2 := 1, a3 := 1, a4 := 5),
         (a1 := 'a', a2 := 0, a3 := 100, a4 := 0),
         (a1 := 'a', a2 := 1, a3 := 100, a4 := 2),
         (a1 := 'X', a2 := 2, a3 := 5, a4 := 4);
END_VAR

Not as compact as C version but still OK.

 

[hapetter]

reply to array of struct

I dont understand how this works for you. I belive code is ok, but I get these strange errors.
Please see screenshot of how I do it and what errors

 

[LadderLogic]

You cannot declare a user data type within a program or among global variables in TwinCAT - you must declare it in "Data Types" section. This is not "C" with its liberties, after all. There are four tabs at the bottom of the project tree: POUs, Data Types, Visualizations and Resources; select "Data Types" and create new type.

The errors related to Global_Vars are caused by the improperly declared BDD structure: since the compiler does not recognize the structure, it objects to declaring the array of it.

A side note: I just noticed that the third tab is called "Visualizations", with 'z'. I am wondering if CoDeSys people thought they were spelling it in American English manner (realize/realise, digitize/digitise etc.)... wrong, of course.

 

[hapetter]

Thank You!
It works just fine now

Its not easy to find all these tricks by myself...

- Hans