Igor Skochinsky / Mbed 2 deprecated FFT

mbed port of FFT routines from STM32 DSP library and Ivan Mellen's implementation. Tested on LPC2368 mbed but should work on 1768 too (original code was written for Cortex-M3)

Dependencies:   mbed

main.cpp@0:90ade34a3b71, 2009-12-13 (annotated)

Committer:
igorsk
Date:
Sun Dec 13 07:14:57 2009 +0000
Revision:
0:90ade34a3b71

        

        
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#include "mbed.h"





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#include <limits.h>





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DigitalOut myled(LED1);





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LocalFileSystem local("local");





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// code from FFTCM3.s by Ivan Mellen





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// http://www.luminarymicro.com/component/option,com_joomlaboard/Itemid,92/func,view/id,1636/catid,6/





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extern "C" void fftR4(short *y, short *x, int N);





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extern "C" void ifftR4(short *y, short *x, int N);





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// code from STM32 DSP Library





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/* 64 points*/





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extern "C" void cr4_fft_64_stm32(void *pssOUT, void *pssIN, uint16_t Nbin);





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/* 256 points */





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extern "C" void cr4_fft_256_stm32(void *pssOUT, void *pssIN, uint16_t Nbin);





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/* 1024 points */





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extern "C" void cr4_fft_1024_stm32(void *pssOUT, void *pssIN, uint16_t Nbin);





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void test_stm32()





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{





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#define N 64 /*Number of points*/





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    uint32_t x[N], y[N]; /* input and output arrays */





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    int16_t real[N], imag[N]; /* real and imaginary arrays */





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    memset(real, 0, sizeof(real));





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    memset(imag, 0, sizeof(imag));





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    real[1]=SHRT_MAX;





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    /* Fill the input array */





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    for (int i=0; i<N; i++)





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    {





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        x[i] = (((uint16_t)(real[i])) | ((uint32_t)(imag[i]<<16)));





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    }





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    cr4_fft_64_stm32(y, x, N); /*computes the FFT of the x[N] samples*/





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    FILE* log = fopen("/local/stm32.txt","w");





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    for (int i=0; i<N; i++)





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    {





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        fprintf(log, "%d: %d, %d -> %d, %d\n", i, real[i], imag[i], int16_t(y[i] & 0xFFFF), int16_t(y[i] >> 16));





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    }





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    fclose(log);    





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}





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void test_mellen()





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{





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    short x[512]; // input data 16 bit, 4 byte aligned  x0r,x0i,x1r,x1i,....





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    short y[512]; // output data 16 bit,4 byte aligned  y0r,y0i,y1r,y1i,....





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    short z[512]; // same format...





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    for (int i=0;i<512;i++) x[i]=0;





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    for (int i=0;i<512;i=i+8)





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      { x[i+0]=16384; x[i+2]=16384;    x[i+4]=-16384;  x[i+6]=-16384;}





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    // x = [ 16384,16384,-16384,-16384,16384,...]  1/4 Fsampling





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    //call functions





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    fftR4(y, x, 256);   // y is in frequency domain y[128]=





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    printf("fftR4 ok\n");





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    ifftR4(z, y, 256);  // z should be x/N + noise introduced by 16 bit truncating 





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    printf("ifftR4 ok\n");





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    FILE* log = fopen("/local/mellen.txt","w");





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    for (int i=0; i<256; i++)





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    {





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        fprintf(log, "%d: %d -> %d -> %d\n", i, x[i], y[i], z[i]);





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    }





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    fclose(log);    





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}





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int main()





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{





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    printf("Testing Mellen\n");





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    test_mellen();





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    printf("Testing STM32\n");





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    test_stm32();





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    printf("Done\n");





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}