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Author Topic: Implementation FFT in C for dsPIC  (Read 15754 times)
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bk3e
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« on: January 17, 2008, 09:27:50 09:27 »

Hi evryone,

I would like to do FFT algorithm in C language for dsPIC. Does anyone help me on this? Thanks
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omidsht
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« Reply #1 on: January 17, 2008, 03:11:23 15:11 »

what does fft do realy ? i have read the fft formula in math in univ , but what it does in practice Huh what want to do with fft in dspic ? would you help me ?

omid
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mris99
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« Reply #2 on: January 17, 2008, 09:59:21 21:59 »

Hello omidsht,
FFT is Fast Fourier Transform. Please check this:
http://en.wikipedia.org/wiki/Fast_Fourier_transform


Hello bk3e,
You should try Microchip dsPIC DSC DSP Algorithm Library.
It contains optimized FFT algorithm in asm, but you can use it from C:

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en023598

Here is also an example for usage:

http://ww1.microchip.com/downloads/en/DeviceDoc/CE018_FFT_DSPlib_101007.zip

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FriskyFerret
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Put it in, take it out.


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« Reply #3 on: January 17, 2008, 11:32:37 23:32 »


Understanding the FFT: A Tutorial on the Algorithm & Software for Laymen, Students, Technicians & Working Engineers



From the publisher
Many engineers, technicians and students are familiar with Fourier analysis and the DFT and, while they know about the fantastic things this technology can do, they are thwarted in their attempts to use these tools because of the advanced level at which the FFT is usually presented. This book explains the FFT and the software at a level that can be handled by advanced high school students and above.

Book Description
This is a tutorial on the FFT algorithm (fast Fourier transform) including an introduction to the DFT (discrete Fourier transform). It is written for the non-specialist in this field. It concentrates on the actual software (programs written in BASIC) so that readers will be able to use this technology when they have finished. Aimed at working engineers, advanced technicians and students.

ISBN-10: 0964568187
Paperback: 180 pages
Publisher: Citrus Press

Links:
http://mihd.net/59ovfd
http://rapidshare.com/files/83370507/Understanding.The.FFT_Zonst_0964568187.rar

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omidsht
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« Reply #4 on: January 19, 2008, 09:21:29 09:21 »

Hi    FriskyFerret   ,  thank you for the book ,
i have downloaded the rapidshare link , when i extract the file , it is  unknown  in my computer (.djvu) , which software hould i open that file  ?
waiting for your guide
thanks

omid
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mcr
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« Reply #5 on: January 19, 2008, 06:29:03 18:29 »

Hi    FriskyFerret   ,  thank you for the book ,
i have downloaded the rapidshare link , when i extract the file , it is  unknown  in my computer (.djvu) , which software hould i open that file  ?
waiting for your guide
thanks

omid


Go here:
http://www.lizardtech.es/download/dl_download.php?detail=doc_djvu_plugin&platform=win

Select english languaje or the one appropiate for you.
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FriskyFerret
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« Reply #6 on: January 19, 2008, 07:05:40 19:05 »

Use WinDjView here: http://sourceforge.net/project/showfiles.php?group_id=114927

or

The DjVu IE Browser Plug-in here: http://www.lizardtech.com/download/dl_options.php?page=doc


Remember, if you use the IE browser plug-in you have to open the .djvu document with Internet Explorer. Give the stand-alone WinDjView a try and let us know if it works well.
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leonardoaraujo.santos
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« Reply #7 on: January 24, 2008, 06:13:40 18:13 »

In simple words... FFT is used to transform some signal from time domain to frequency domain, but with litle computation effort compared with other mathematical tools... like DFT...

This is very important on real-time DSP applications because all computation must be done before the next sample of information becomes avaible.

For example... Imagine that you have an voice recorder, and in the middle of the record process. you place an gadget (DSP board) that filter high frequency components....

The Gadget must be able to process the filter in (1/20000) seconds.. in order to keep recording the voice without any "pops" or strange sounds generated by bad sampling.
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bk3e
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« Reply #8 on: January 29, 2008, 03:19:44 03:19 »

Hi, everyone. I still haven't understood how to emplementation FFT algorithm for dsPIC by C language. Please explain clearly to me and flow chart of this algorithm.
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rinderpest
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« Reply #9 on: February 13, 2008, 02:18:23 02:18 »

@bk3e:
You cant expect everyone to do your homework for you, someone kindly gave you a book; if you read this and the wikipedia article it will give you a start on the information you need - as it stands you're asking someone to do dozens of hours work for you!
You should try to understand what you can from the book and websites then come back and ask a much less general question. When you just ask identical question again it seems you havent listened to what people have showed you already.
If you read up on this and then ask questions about what you have read and tried then people will work with you.
I know it sounds harsh but people prefer to help those who try to help themselves.
You should also read the Mikroelectronica forum in the DsPIC section; there is an FFT library which is discussed in detail, in C and BASIC.
Good Luck
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« Reply #10 on: February 20, 2008, 10:16:56 22:16 »

FFT's can take some hours to grasp. Get your self a good engineering maths book then a good engineering control theory book. I am on the second year of my degree so far and its still taken me some hours to fully understand it but the best way is with a real world problem and then work on the theory and solving the problem at the same time.

Adam
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« Reply #11 on: April 04, 2008, 10:36:25 10:36 »

Here is a good tutorial about using dsPIC for digtal filter design:

http://www.mikroe.com/en/books/dspicbook/15.htm

Best Regards.
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« Reply #12 on: April 05, 2008, 12:25:33 00:25 »

http://www.mars.dti.ne.jp/~m7030/
intelligent projects......far east.
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« Reply #13 on: July 06, 2008, 02:31:36 14:31 »

Hi use mikroc for dspic it have in built  simple fft function:

void Fft(unsigned log2N, const unsigned *TwiddleFactorsAddress, unsigned *Samples);
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alichan
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« Reply #14 on: January 16, 2009, 11:52:35 11:52 »

Since you are not working with analog signals in the pic, because when you convert to digital you are discretizing, you can't use Fourier Transform. You have to use DFT (Discrete Fourier Transform).

FFT is only a way to make easiest the complex calculations involved in DFT, reducing them and increasing resolution.

If you don't understand DFT hardly will understand FFT. Wink
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