Curt Corum,
I am not familiar with the FFTW libraries, but if they are DLL's you can call them using the Call Library Funciton Node. Additionally, you can use the Code interface node if they simply .c files. Please look at
this forum post for additional information from customers who have the same situation as you. Here at NI we do not use this third-party libraries because LabView has its own FFT functions so the best source of information is to dig through our forums and find post from customers who do use these libraries.
If you need help with the Call Library Function Node, there is a really good example in the LabView example finder. You can get to the example finder by going to the help menu and selecting Find Examples...
Once you are in the example finder click the Search Tab and search for Call DLL. This example is very extensive and it shows you how to handle different data types.
Eli S.
National Instruments
Applications Engineer