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[/] [versatile_fft/] [trunk/] [multiple_units/] [test_fft.m] - Rev 3
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% Modify the length of the FFT in the line below log2fftlen = 4; % If you modify the number of bits used to represent % real and imaginary part of the complex number, % you should also modify the ICPX_WIDTH constant % in the icpx_pkg.vhd file icpx_width = 16; % Do not modify below % Write the package defining length of the FFT fo=fopen("src/fft_len.vhd","w"); fprintf(fo,"package fft_len is\n"); fprintf(fo,"constant LOG2_FFT_LEN : integer := %d;\n",log2fftlen); fprintf(fo,"constant FFT_LEN : integer := 2 ** LOG2_FFT_LEN;\n"); fprintf(fo,"constant ICPX_WIDTH : integer := %d;\n",icpx_width); fprintf(fo,"end fft_len;\n"); fclose(fo) fftlen=2 ** log2fftlen; %Generate the data. Now it is only a noise, but you %can generate something with periodic components %It is important, that values fit in range of representation %(-2,2) for standard implementation. %May be changed if you redefine our icpx_number format %To check that calculation of spectrum for overlapping windows %works correctly, we generate a longer data stream... len_of_data=fftlen*5 re=3*rand(1,len_of_data)-1.5; im=3*rand(1,len_of_data)-1.5; fo=fopen("data_in.txt","w"); for i=1:len_of_data fprintf(fo,"%g %g\n",re(i),im(i)); end fclose(fo) %Create the Hann window. %Remember, that you must use the same window function %in your VHDL code! x=0:(fftlen-1); hann=0.5*(1-cos(2*pi*x/(fftlen-1))); %Now we calculate the FFT in octave scale = 2 ** (icpx_width-2); fo=fopen("data_oct.txt","w"); for i=1:(fftlen/2):(len_of_data-fftlen) x=i:(i+fftlen-1); di = (re(x)+j*im(x))*scale/fftlen; fr = fft(di.*hann); % fr = fft(di); fprintf(fo,"FFT RESULT BEGIN\n") for k=1:fftlen fprintf(fo,"%d %d\n",floor(real(fr(k))),floor(imag(fr(k)))); end fprintf(fo,"FFT RESULT END\n") end fclose(fo) %Run the simulation system("make clean; make") %Compare results calculated in octave and in our IP core system("vim -d data_oct.txt data_out.txt")