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FFT algorithm

ChungHustVN

Hello everyone. I write FFT, it's ran! But it run very slow speed, I try on STM32F103C8T6 72MHz and used timer to measure time, the result about 360ms and I can't run another program. Somebody help me please! Thank all!

My code here: the DFT http://codepad.org/vwMlHR1V

and FFT : http://codepad.org/HbDwS2TZ

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    Ok, what do you expect? You are doing a lot of float and double operations on a micro controller w/o FPU.

    But there are also "programming faults":

        WR = cos(-PI * k / N);
	WI = sin(-PI * k / N);

    Try using "cosf" (float) not "cos" which is double.

    Note: The compiler will use double unless you explicitly tell it to use float!
    So PI should be defined like this:

    #define PI      3.1415926535897f

    Maybe switch to fixed point math.

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  • 0

    Ok, what do you expect? You are doing a lot of float and double operations on a micro controller w/o FPU.

    But there are also "programming faults":

        WR = cos(-PI * k / N);
	WI = sin(-PI * k / N);

    Try using "cosf" (float) not "cos" which is double.

    Note: The compiler will use double unless you explicitly tell it to use float!
    So PI should be defined like this:

    #define PI      3.1415926535897f

    Maybe switch to fixed point math.

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