Error: "Object Reference Not Set To An Instance Of An Object"

[nima1985]

Hi,

I have c++ code which I wrapped (so it's being used as a dll), and I call the functions in vb.net.

 

The C++ code calls functions (which work, coz I tested it in other programs) from a PCI card hooked up to the CPU.

 

In C++ the function which I call is:

 

 

 

extern "C" __declspec( dllexport ) int _stdcall GPS637Time(float *time, float *week)

{

UCHAR getpacket[80], sendpacket[80]; // Receive buffer

 

GpsPkt receive;

GpsPkt send;

int n;

int s;

 

send.len = 1;

send.id = 0x37;

send.data =sendpacket ;

receive.len = 20;

receive.id = 0x41;

receive.data = getpacket;

 

s = bcGPSMan (&send, &receive);

for (n=0;n!=100;n++){

if (s!=RC_ERROR) break;

s = bcGPSMan (&send, &receive);

}

if (s == RC_OK)

{

*time = (float)(convertf(&getpacket[0]));

*week=(float)(convertf(&getpacket[4]));

return RC_OK;

}

return RC_ERROR;

}

 

 

 

bcGPSMan(..) is from the PCI card.

the helper function is:

 

 

 

float convertf (char *s)

{

union {

float f;

char uc[4];

} fconv;

fconv.uc[3] = *(s++);

fconv.uc[2] = *(s++);

fconv.uc[1] = *(s++);

fconv.uc[0] = *s;

return fconv.f;

}

 

 

In VB.NET, I declare the dll function:

 

Private Declare Function GPS637Time Lib "GPS637Wrapper.dll" (ByRef time As Single, ByRef week As Single) As Long

 

 

And call it:

 

Dim ok As Long

ok = GPS637Time(time, week)

 

Where I get the above error message.

 

Can ANYONE pleaseeeeeee help me? :-\

Thank You!! :)

[FZelle]

Long in VB.NET is 64Bit.

Use Integer .

[nima1985]

Thanks for the reply.

 

I made "ok" be an Integer, and I made the declaration for the function return an Integer.

It still causes the error.

I think it might have something to do with the parameters.

I tested the c++ code using just c++, and sending pointers to the function. I think the way I send variables in vb.net is incorrect. :s I'm not sure wut to do next.. How else can i send the variables in vb.net?? :confused:

[techmanbd]

ok = GPS637Time(time, week)

 

time and week. Where did you declare them and how did you declare them?

[nima1985]

I declared them in vb.net right before the GPS637Time(..) function.

 

Dim time, week as Single

 

I even tried to create new objects with time and week but it still created the error:

 

time = new Single

week = new Single