Convert C++ dll function declaration to VB *RESOLVED*

[Simon Caiger]

Hi,
I have a C++ dll which has the following function prototype declared in it.

Short Int Send_RS232_Command(unsigned char, unsigned char *const, unsigned char, unsigned char *const, long)

I am trying to use this dll from VB.
Code I have so far is.

Option Explicit
Option Base 0
 
Private Declare Function Send_RS232_Command Lib "RS232V2.dll" Alias "?Send_RS232_Command@@YAFEQAEE0J@Z" _
                        (ByVal bBoardAddress As Byte, ByRef bTxDataArray As Byte, _
                        ByVal bTxDataLength As Byte, ByRef bRxDataArray As Byte, ByVal lRxDataLength As Long) As Integer
 
Private Sub cmdSend_Click()
 
    Dim iRet As Integer
    Dim bBoardAddress As Byte
    Dim bTxDataArray(10) As Byte
    Dim bTxDataLength As Byte
    Dim bRxDataArray(10) As Byte
    Dim lRxDataLength As Long
    
    bBoardAddress = 1
    bTxDataArray(0) = 0
    bTxDataArray(1) = 1
    bTxDataArray(2) = 2
    bTxDataArray(3) = 3
    bTxDataArray(4) = 4
    bTxDataLength = 5
    
    iRet = Send_RS232_Command(bBoardAddress, bTxDataArray(0), bTxDataLength, bRxDataArray(0), lRxDataLength)
 
End Sub

I get the error "Bad DLL Calling Convention".
Is this because I have incorrectly declared the function?

[Simon Caiger]

So I did the usual self doubting, am I going mad bit for a couple of hours and then I discovered that I have been wrestling with another Microsoft bug.

http://support.microsoft.com/default...;en-us;Q153586

You can not call a C function in a dll from the VB IDE if the function uses the _cdecl calling convention.

If you compile and run the VB .exe, it works fine.

Not to good for debugging then

[azteched]

Do you have the DLL source? If so change the calling convention to __stdcall and it will work through the IDE.

[Simon Caiger]

Thanks for the reply.

Thats what the Knowledge Base article I linked to suggests.

Unfortunately, I do not have the source code

[BuggyProgrammer]

You can write a dll in c++ that calls your RS232 dll, and have your vb program call your dll. This way, you could make your dll have the stdcall.