LabVIEW and DLL

[Oesen]

Hi

I'm making a project based on video acquisition with NI-IMAQdx. The goal here, is to grab images from an USB webcam, converting the images to arrays of pixel values, and then exporting those arrays to a buffer, which is implemented in C. Due to that, I have the idea to sending those arrays of pixel values continuously to a DLL file as an output, so I can catch them continuously with an external C-program and directly export the arrays to the buffer from the DLL file. As can be seen in the block diagram, I managed to export the arrays continuously to a .csv file, and I want exactly the same procedure to a DLL file, but don't know how to do it.

[Dennis_Knutson]

Do you have the dll written and compiled. Does the dll accept a 2D array of U32?

There is the wizard that allows you to import a dll as long as you have the .h file with the exported functions.

[Oesen]

Hi Dennis

I have builded a DLL file by creating a project from this VI, and then choosing "Shared library DLL" from the build specifications. I only want the arrays in this DLL file. I have figured out, that I also can use those two blocks in the block diagram shown on the picture. What is the benefits of using them ?.

[Dennis_Knutson]

Sorry but you are not making any sense. You can make your subVi that you posted into a dll but you can't then call that dll from the same  VI like you asked. I have no idea what you are trying to do now. 

Those images are senseless to me. You should know the function names.

[Oesen]

The main purpose with this VI, is to send or export 5 frames (arrays of pixel bytes) per second to a c-code. That's why I will created this DLL file. I don't want to call that DLL file from a VI. I have to call it from my c-code.

[Dennis_Knutson]

The image in your first message shows you with a call library function node. That means you wanted to call a dll from the VI. If you want to call that VI from a c program, then build it but you have to modify it and eliminate the while loop like I already told you in a previous thread.

You still haven't said what those functions are in your other image.

In yet another thread you started, you were told the c program could call the imaq functions and you could skip LabVIEW. Why aren't you doing this?

[Oesen]

Hi Dennis

That call library function node was just a confusion, it shouldn't be there, sorry. The other problem is that, I use the while loop to adjust the captured frames per second with the grab function. If I eliminate it, I can't adjust it anymore.

In the other thread, they suggested me to call the IMAQdx functions from C, but video acquisition seems to be difficult in C compared to LabVIEW. That's why I used this solution instead

[Dennis_Knutson]

The while loop stops when you have an error or when the stop button is pressed. You need to determine another way.

[Oesen]

I have tried a lot and concluded that I'll transmit the arrays by using the TCP/IP method instead.