main.cpp

00001 #include "mbed.h"
00002 #include <limits.h>
00003 
00004 DigitalOut myled(LED1);
00005 LocalFileSystem local("local");
00006 
00007 // code from FFTCM3.s by Ivan Mellen
00008 // http://www.luminarymicro.com/component/option,com_joomlaboard/Itemid,92/func,view/id,1636/catid,6/
00009 extern "C" void fftR4(short *y, short *x, int N);
00010 extern "C" void ifftR4(short *y, short *x, int N);
00011 
00012 // code from STM32 DSP Library
00013 /* 64 points*/
00014 extern "C" void cr4_fft_64_stm32(void *pssOUT, void *pssIN, uint16_t Nbin);
00015 /* 256 points */
00016 extern "C" void cr4_fft_256_stm32(void *pssOUT, void *pssIN, uint16_t Nbin);
00017 /* 1024 points */
00018 extern "C" void cr4_fft_1024_stm32(void *pssOUT, void *pssIN, uint16_t Nbin);
00019 
00020 void test_stm32()
00021 {
00022 #define N 64 /*Number of points*/
00023     uint32_t x[N], y[N]; /* input and output arrays */
00024     int16_t real[N], imag[N]; /* real and imaginary arrays */
00025     memset(real, 0, sizeof(real));
00026     memset(imag, 0, sizeof(imag));
00027     real[1]=SHRT_MAX;
00028     /* Fill the input array */
00029     for (int i=0; i<N; i++)
00030     {
00031         x[i] = (((uint16_t)(real[i])) | ((uint32_t)(imag[i]<<16)));
00032     }
00033     cr4_fft_64_stm32(y, x, N); /*computes the FFT of the x[N] samples*/
00034     FILE* log = fopen("/local/stm32.txt","w");
00035     for (int i=0; i<N; i++)
00036     {
00037         fprintf(log, "%d: %d, %d -> %d, %d\n", i, real[i], imag[i], int16_t(y[i] & 0xFFFF), int16_t(y[i] >> 16));
00038     }
00039     fclose(log);    
00040 }
00041 
00042 void test_mellen()
00043 {
00044     short x[512]; // input data 16 bit, 4 byte aligned  x0r,x0i,x1r,x1i,....
00045     short y[512]; // output data 16 bit,4 byte aligned  y0r,y0i,y1r,y1i,....
00046     short z[512]; // same format...
00047     
00048     for (int i=0;i<512;i++) x[i]=0;
00049     for (int i=0;i<512;i=i+8)
00050       { x[i+0]=16384; x[i+2]=16384;    x[i+4]=-16384;  x[i+6]=-16384;}
00051     // x = [ 16384,16384,-16384,-16384,16384,...]  1/4 Fsampling
00052     
00053     //call functions
00054     fftR4(y, x, 256);   // y is in frequency domain y[128]=
00055     printf("fftR4 ok\n");
00056     ifftR4(z, y, 256);  // z should be x/N + noise introduced by 16 bit truncating 
00057     printf("ifftR4 ok\n");
00058     FILE* log = fopen("/local/mellen.txt","w");
00059     for (int i=0; i<256; i++)
00060     {
00061         fprintf(log, "%d: %d -> %d -> %d\n", i, x[i], y[i], z[i]);
00062     }
00063     fclose(log);    
00064 }
00065 
00066 int main()
00067 {
00068     printf("Testing Mellen\n");
00069     test_mellen();
00070     printf("Testing STM32\n");
00071     test_stm32();
00072     printf("Done\n");
00073 }