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Throw Exceptions in CODESYS

How can I throw standard system exceptions (and if possible, create custom exceptions and throw them too).

The simplest thing that comes to mind, is to just divide a variable by zero, but that's just a hack at best.

I did find mentions of a function AppGenerateException in the CmpApp library, but I can't find any documentation for it, nor any examples. Can anybody point me to some documentation for this?

Solution

  • Out of curiosity I checked the AppGenerateException and got it working. Got some help from this Codesys help page.

    I still think this is not the best way to achieve what you need, but it could work.

    Unfortunately, I have 64 bit system and the TRY..CATCH is not yet working in other that 32 bit systems as far as I know, so I couldn't test catching.

    Add the following libraries:

    • CmpApp
    • SysExcept

    Then the following code seems to work. Set ThrowErr to true to get the system exception.

    PROGRAM PRG_TestThrow
VAR CONSTANT
    MY_PRIVATE_EXCEPTION : DWORD := 32001;
END_VAR
VAR
    ThrowErr    : BOOL; //Set this to TRUE to throw an error

    //The next two are for getting App instance
    _pApp       : POINTER TO CmpApp.APPLICATION;
    _Result     : SysExcept.SysTypes.RTS_IEC_RESULT;
END_VAR



//Get App instance
_pApp := AppGetCurrent(pResult := ADR(_Result));

IF ThrowErr THEN
    ThrowErr := FALSE;

    IF _pApp <> 0 THEN
        //Throw divide by zero exception
        AppGenerateException(pApp:=_pApp,   ulException:=RtsExceptions.RTSEXCPT_DIVIDEBYZERO);

        //You could use probably any available number as your own custom exception. 
        //For example the following works BUT not sure if it's ok to this.
        //AppGenerateException(pApp:=_pApp,   ulException:=MY_PRIVATE_EXCEPTION);

        //See RtsExceptions type for available exception codes. 
        //For my Codesys version, it has largest exception number of 0x2000 so all larger number are free (for now...)
    END_IF
END_IF

    It seems that it's possibly to use any custom exception code like:

    AppGenerateException(pApp:=_pApp,   ulException:=MY_PRIVATE_EXCEPTION);

    But it's not documented so I would be careful.