function [time, data] = ReadRedBoardData_v1(serialPort, nSkips, nMax,opFilename)
% A simple function to read single channel data from the RedBoard and save as a
% time-stamped, two-column array of length nMax as  opFilename.mat file
%
% Input arguments: 
% serialPort - char specification of the COM port name your RedBoard is using
% nSkips - no of received points to skip from saving/analysis etc.
% nMax - no of points to save/analyze after skipping nSkips points
% opFilename - char string for the file name to be saved in MATLAB binary format (.mat)
%
% Output arguments:
% time - time vector AFTER first nskips points are skipped. 
% These are time-stamps collected using the toc command at the instant when the data is 
% received from the serial port. So the output data is NOT sampled at fixed-freuqency.
% data - the single channel floting point data acquired from serialPort ('%f')
%
%
% Last Updated: May 13, 2020
% ------------------------------------------------------------------------------------------------------------
% Created By:
% Anil Maybhate
% Whiting School of Engineering | Johns Hopkins University
% 3400 N. Charles St., Baltimore, MD 21218 USA
% Email: anil.maybhate@jhu.edu
% ------------------------------------------------------------------------------------------------------------

% total No of points read from the redboard
N=nSkips+nMax;

% initialization of required arrays and variables
time = zeros(1,N);
data = zeros(1,N);
count = 0;

% Define the serial object and open communication with the specified COM port.
% BaudRate is default (9600). Do NOT change it.
s = serial(serialPort);
fopen(s);

% start stopwatch
tic;

% loop to read and store incoming data, store current stopwatch time
while count<N
    count = count+1;
    value = fscanf(s,'%f');                                 
    data(count)=value(1);
    time(count) = toc; 
end

% close the serial port cmmunication and delete the used serial object variable
fclose(s); clear s;

% delete nskips no of initial data points to allow the equillibriated time series to be recorded
time=time(nSkips+1:end);
data=data(nSkips+1:end);

% plot data
plot(time,data)
xlabel('time (seconds)','FontSize',16);

% save time-stamped data in a 2-column vector in MATLAB binary format ('.mat')
time=time'; data=data'; tECG=[time data]; % transpose and combine into a 2-column array (nMax by 2)
save(opFilename,'tECG')
end