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Calling a Function node in a DLL to give force-feedback effect to a joystick (using DirectInput)

Hello,

 

I have been working for a couple of weeks on writing a DLL in Visual C++ Studio. My intention is to write an exported function in the DLL to initialize a Logitech Force3Dpro joystick, setup a force feedback effect and run it using DirectInput. I would like to control this force feedback effect (in particular, the intensity of the feedback) from Labview by calling the function in the DLL.

 

I followed the FFConst example in Microsoft SDK DirectInput Samples for making an .exe file to setup and run force feedback effects. I have been able to build the DLL successfully with an exported function that can be accessed from Labview by "Call a function node". I tested the function by running simple functions such as addition and multiplication of integers, andconfirmed the fact that the DLL was built correctly. I have also included the DirectInput code for initializing and running the force feedback effect. I am able to compile and build the DLL with no problems.

 

The Problem:

The only problem that I have at this point is with setting SetCooperativeLevel for the DirectInput8 joystick device. I have to provide a top-level window handle to SetCooperativeLevel so that I can give the function exclusive access to the joystick. Since I am not making a window and am building a DLL, I am not sure what handle I am supposed to provide it so that the joystick can respond. I am not sure if passing a handle to the Labview window would work because it is accessing the DLL's function? I tried passing LabView window handle to the function and read the X-axisposition off the joystick, but it read some junk (huge long integer) - which lead me to believe that the problem is something to do with initializing the joystick.

 

For all practical purposes, I am a complete novice at DirectInput programming and working with Visual C++. Although, I have programmed in C++previously. I am sorry for the long message, but I wanted to give a bit of background so that my aim is clear.

 

Any help, advice or direction with this problem be very much appreciated. Thank you for your time!

Cheers!

Abhishek

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