%function Xk = myfft(xn)
%256 fft, matlab1，c0 start
clc;
clear;
Adc=2; %
A1=3; %F1
A2=1.5; %F2
F1=50; %1(Hz)
F2=75; %2(Hz)
Fs=256; %(Hz)
P1=-30; %1()
P2=90; %()
N=256; %
t=[0:1/Fs:(N-1)/Fs]; %
%
S=Adc+A1*cos(2*pi*F1*t+pi*P1/180)+A2*cos(2*pi*F2*t+pi*P2/180);
xn=1:1:256;
%Xk=S;
M=8;
nixueshu=[0,128,64,192,32,160,96,224,16,144,80,208,48,176,112,240,8,136,72,200,40,168,104,232,24,152,88,216,56,184,120,248,4,132,68,196,36,164,100,228,20,148,84,212,52,180,116,244,12,140,76,204,44,172,108,236,28,156,92,220,60,188,124,252,2,130,66,194,34,162,98,226,18,146,82,210,50,178,114,242,10,138,74,202,42,170,106,234,26,154,90,218,58,186,122,250,6,134,70,198,38,166,102,230,22,150,86,214,54,182,118,246,14,142,78,206,46,174,110,238,30,158,94,222,62,190,126,254,1,129,65,193,33,161,97,225,17,145,81,209,49,177,113,241,9,137,73,201,41,169,105,233,25,153,89,217,57,185,121,249,5,133,69,197,37,165,101,229,21,149,85,213,53,181,117,245,13,141,77,205,45,173,109,237,29,157,93,221,61,189,125,253,3,131,67,195,35,163,99,227,19,147,83,211,51,179,115,243,11,139,75,203,43,171,107,235,27,155,91,219,59,187,123,251,7,135,71,199,39,167,103,231,23,151,87,215,55,183,119,247,15,143,79,207,47,175,111,239,31,159,95,223,63,191,127,255];
nixue=nixueshu+1;
for n=1:256;
m = nixue(n);
Xk(n)=S(m);
end
W = exp(-j*2*pi/256);
for L=1 : M
for k=0 : N/(2^L)-1
for m = 1:2^(L-1)
n = m + 2^(L-1);
temp = Xk(m+k * 2^L);
r = (m-1)*2^(M-L);
Xk(m+k*2^L) = temp + exp(-j*2*pi*r/256)*Xk(n+k*2^L);
Xk(n+k*2^L) = temp - exp(-j*2*pi*r/256)*Xk(n+k*2^L);
end
end
end
XXk=abs(Xk);
plot(XXk);