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Cannot access function in C DLL with VB

Hi,

I'am having difficulties in VB with the use of a function call in a certain C DLL.

The DLL function is described below. There is a struct in it aswell.
Hopefully you have an answer to this. I tried a lot but nothing will work.

int IOTSVC_API iotsvc_Open(unsigned long *pulHandle, char *csTarget, iotlayout_t *pLayout);

typedef struct
{
unsigned char ucType;
char csName[16];
unsigned short usTotalNoInputs;
unsigned short usNoAnalogeInputs;
unsigned short usNoDigitalInputs;
unsigned short usTotalNoOutputs;
unsigned short usNoAnalogeOutputs;
unsigned short usNoDigitalOutputs;
} iotmodule_t;

typedef struct
{
unsigned short usTotalNoInputs;
unsigned short usTotalNoOutputs;
unsigned short usNoIOmodules;
iotmodule_t IOmoduleInfo[MAX_NO_IO_MODULES];
} iotlayout_t;

How should i declare this in VB and how can i access the C function in VB.

Thank for your help

AVI

ASKER CERTIFIED SOLUTION

sudhakar_koundinya

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Smallint

Hi AVsystem,

C function must be defined with _stdcall

Take a look here, may is helpful for you

https://www.experts-exchange.com/questions/20608530/calling-dll-from-vb6-with-struct-argument.html

Cheers

AVsystem

ASKER

Hi, AVsystem here,

It still wo'nt work.

Probably the data definitions are not mapped from C to VB.
There is defined an unsigned long, unsigned short and a unsigned char.
Is there someone that has enough expierience to tackle this for me.

Greetings AVI