Hi! I am a newcomer in calling DLLs from LAbview...
I am trying to implement FFTW (fastest fourier transform in the west) in LV. Though a windows DLL already exists,
I fear that it is quite impossible to work it directly under LV. Can you check me if this is correct?
this is what I would be supposed to do in C
1) Create a so-called "plan", specifying input and output addresses
plan = make_plan(double *array_in, double *array_out)
2) Execute the plane
fftw_execute(plan).
In C this makes the memory pointed by array_out being updated. In labview it does not... Therefore it seems that such a
programming-style is not supported by LV. Correct?
And, btway, plz help me in understanding what's happening:
1a) I wire,e.g., a 1D array to a DLL (as *double); now, let's suppose, like in the aforementioned case, that the DLL does not do anything
on the array (neither read nor write), but simply "gets prepared" for doing something later. I can suppose that, somewhere in the memory,
it keeps tracks of the memory address of the data it has received.
2b) Another DLL call, that takes advantage of the information stored by the previous call, reads data in memory and perform calculations.
The questions are:
- If between 1 and 2 I change the value of the ARRAY in LV, the second call reads the proper (new) values?
- If not, what the hell happens to the pointer passed to the DLL in the step 1??? I mean, I LV REALLY PASSED THE DLL the memory address where data
are stored, I could effectively perform operations on them from everywhere in my operative system... but it seems that i CAN'T!!
Is there a place where I can find an in-depth documentation to such a stuff??
Thank you very muche,
michele
