How to find FFT of the values generated from signal generator using Arduino?

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Chandrika Avvaru 2018-12-20

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https://ww2.mathworks.cn/matlabcentral/answers/436616-how-to-find-fft-of-the-values-generated-from-signal-generator-using-arduino

评论： Mark Sherstan 2019-1-30

I have a data of values recorded from signal generator using aduino.I would like to find the fft of the signals.I gave a 15Hz sine wave with amplitude 2Vpk-pk but I am getting the wrong fft.Please help me.

X=load('data3.txt');
fs=256;
T=1/fs;
L=10000;
t = (0:L-1)*T;
Y=fft(X);
P2 = abs(Y/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);       
f = fs*(0:(L/2))/L; 
plot(f,P1); 
title('FFT Plot of a signal')

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Chandrika Avvaru 2018-12-24

That is where I got stuck.I don't know the sampling frequency.How can I find?

Mark Sherstan 2019-1-30

Theres lots of different ways but you could rerun your data acquistion and print a timer to record how long it takes to execute one loop (e.g. using micros(); on the Arduino). Then use MATLAB to calculate the difference between time steps using the diff function and average the vector to get an approximation of the sampling rate.

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