Square Wave FFT

			
				clc; clear;

				fs = 128; % sampling rate
				N = 1024; % samples
				fi = 5; % 5 Hz

				t = 0 : 1/fs : 1; % time vector
				x = square(2*pi*fi*t); % square wave

				subplot(2,1,1);
				plot(t,x); % plot square wave
				ylim([-1,1.5]);
				xlabel('time');
				ylabel('amplitude');
				title('square wave');

				y = fft(x,N); % fft
				Y = abs(y(1:N/2+1)); % make single-sided
				f = fs/2*linspace(0,1,N/2+1); % freq vector
				YdB = mag2db(Y); % in dB
				YdB = YdB - max(YdB); % scale to 0dB

				subplot(2,1,2);
				plot(f,YdB); % plot FFT
				xlabel('freq');
				ylabel('magnitude');
				title('FFT');
				grid on;