Subversion Repositories versatile_fft

% 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")