%  =======================================================================
%  Matlab Data Import and Real Time Plotting
%
%  By Patrick Yukman
%  Dartmouth College
%  =======================================================================

%%
%  The port name will be system dependent. On different systems it might
%  look like:
%
%  Linux: port = '/dev/ttyS0';
%  MacOS: port = '/dev/tty.usbmodemfa141';
%  Windows: port = 'COM1';
%
%  But it will need to be correctly configured before you can receive any 
%  data!
clear all;
port = 'COM3';

%%
%  Variables
X_SIZE = 5000;

%%
%  This code serves to open the serial port for communication between the
%  Arduino and the computer.
in = serial(port);
set(in, 'BaudRate', 115200);
set(in, 'Parity', 'none');
set(in, 'DataBits', 8);
set(in, 'StopBits', 1);
set(in, 'InputBufferSize', 1000);
fopen(in);

%%
%  This code will open and set up an external file to which the data will
%  be separately written.
date = datestr(now);
dateString = strrep(date, ' ', '_');
dateString = strrep(dateString, ':', '');
dataTitle = ['DataInput_' dateString '.txt'];
dataFile = fopen(dataTitle,'w');
disp(['Data being written to ' dataTitle]);

%%
%  Now we will set up the figure window.
voltages = zeros(1,X_SIZE);
xSpacing = linspace(1,X_SIZE,X_SIZE);
dataLine = plot(xSpacing,voltages);
ylim([0 1023]);

%%
%  Now we read data in through the serial port.
tline = 1;
count = 1;
while (tline ~= -1)
    %  Read a line from the serial port, write it to a file, and plug it
    %  into the voltages vector.
    tline = fgets(in);
    fprintf(dataFile,tline);
    num = str2num(tline);
    voltages(count) = num;
    %  Increment count all the way to X_SIZE, then start at the beginning
    %  again. This lets us keep writing over the elements of voltages, so
    %  the script doesn't get bogged down with memory allocation and 
    %  massive vector structures.
    if count <= (X_SIZE - 1)
        count = count + 1;
    else
        count = 1;
    end
    %  Only redraw once every 25 data points. This allows the plotting to
    %  happen relatively fast. Plotting each data point from the Arduino,
    %  which is running at ~1000 Hz, would slow the script down so much
    %  that the Arduino's data buffer would fill up.
    if mod(count,25) == 0
        set(dataLine,'YData',voltages);
        drawnow;
    end
end