Fast Fourier Transform

[Anders Björk]

QUOTE (Phantom_Lord @ Sep 15 2008, 10:47 PM)

I think you are referring to the point by point section: I tried that, but I would prefer using spectral measurement because it supports windowing and averaging without further coding...

Thanks for your reply!

Well you have this Vi that uses waveform input and not Dynamical inputs which expressvis do.

http://lavag.org/old_files/monthly_09_2008/post-5713-1221561700.jpg' target="_blank">

[Phantom_Lord]

QUOTE (Anders Björk @ Sep 16 2008, 10:41 AM)

Well you have this Vi that uses waveform input and not Dynamical inputs which expressvis do.

http://lavag.org/old_files/monthly_09_2008/post-5713-1221561700.jpg' target="_blank">

Yes, in fact I've done in a similar way; I've downloaded the circular buffer VI but it doesn't work with my labview version.

This is however a simplified version of what is going on in my VI (the FFT here is done on 10 samples and is updated every sample).

[Anders Björk]

QUOTE (Phantom_Lord @ Sep 16 2008, 07:21 PM)

Yes, in fact I've done in a similar way; I've downloaded the circular buffer VI but it doesn't work with my labview version.

This is however a simplified version of what is going on in my VI (the FFT here is done on 10 samples and is updated every sample).

It is the first time I have seen the use of feedback for implementing a circular buffer.

[Scott Carlson]

Its just an uninitialized shift-register. Only can be hard to decypher if your not used to them.

QUOTE (Anders Björk @ Sep 16 2008, 03:39 PM)

It is the first time I have seen the use of feedback for implementing a circular buffer.

[Anders Björk]

QUOTE (Scott Carlson @ Sep 16 2008, 10:09 PM)

Its just an uninitialized shift-register. Only can be hard to decypher if your not used to them.

I have you used they "old" shift registers my impression is that these are hard to read because of the backflowing wires. So I agree.

[Phantom_Lord]

QUOTE (Anders Björk @ Sep 16 2008, 07:39 PM)

It is the first time I have seen the use of feedback for implementing a circular buffer.

How would you implement it? I used this because it was the first to come into my mind, given my limited knowledge of labview

[Marijn]

Hi,

Thanks for the guru example, I had no porblem getting a 2d transform to work. But I can't get the inverse fft to work. Setting the directionality to (1) instead of (-1) for the forward still results in the forward fft. It seems like the call library node doesn't pass the sign correctly to the fftw dll. Do any of you have advice on how to prperly address the fftw dll to obtain the backward transform?

Thanks, Marijn

[Dirk J.]

Here's an updated example, implementing forward and inverse FFT, in 1D and 2D.

enjoy /dirk.

[tfroess]

Here's an updated example, implementing forward and inverse FFT, in 1D and 2D.

enjoy /dirk.

Sorry for the necro post... but I am interested in the FFTw implementation. Has the attachements been removed for old posts?

[Yair]

Has the attachements been removed for old posts?

 

A lot of them were lost in a server crash a few years back. You can clicking the report link on the relevant post and ask the moderators to look for the file, but I wouldn't hold my breath on that, as I don't know what tools they for that and if it's even still possible. If it's a useful file, then someone else might have it.

[GregSands]

I have two zip files from that era which look promising (i.e. they have FFTW in their titles!).

LAVA_FFTW.zip

FFTW_1D_2D__forward_and_inverse.zip

 

The Multicore Toolkit is another option for fast, parallelized FFTs. http://sine.ni.com/nips/cds/view/p/lang/en/nid/210525

 

[tfroess]

The Multicore Toolkit is another option for fast, parallelized FFTs

Thanks for the uploads. I will check them out.

"NI LabVIEW Multicore Analysis and Sparse Matrix Toolkit  CAD 1,715.00" Pretty hefty price tag for something readily available in other languages for free.

[Kas]

Above FFTW only works for 32 bit versions. It was simple enough to grab the 64 bit DLL version from FFTW website and replace it. 

Attached is for both 32 and 64 bit version. 

LAVA_FFTW (32 and 64 bit).zip