plot data in real time using tcpip connection with matlab - matlab

Question

I connect my iPhone and matlab with the tcpip function.
I need to plot the data in real time (and before make some calculations with the data).
I used real_time_data_stream_plotting.m which I found in internet.
%% Real Time Data Stream Plotting Example
function real_time_data_stream_plotting
%%
% This example demonstrates how to automatically read a set number of data bytes as and
% when they are available. This MATLAB(R) script also generates a real time plot of streaming
% data collected from the TCPIP server.
%
% The script may be updated to use any instrument/device/TCPIP server
% to collect real time data. You may need to update the IP address and
% port.
%
% To generate a report of this entire script, you may use the PUBLISH
% command at the MATLAB(R) command line as follows:
%
% publish(real_time_data_plot);
% Author: Ankit Desai
% Copyright 2010 - The MathWorks, Inc.
%% Create the interface object
% Create a TCPIP object listening to port 19 (Character Generator).
%
% *Note* : To enable character generator service at port 19 on a Windows platform, enable:
%
% Control Panel > Add Remove Programs > Add/Remove Windows Component > Networking Services
%
interfaceObject = tcpip('192.168.1.111',52928);
%%
% Setup a figure window and define a callback function for close operation
figureHandle = figure('NumberTitle','off',...
'Name','Live Data Stream Plot',...
'Color',[0 0 0],...
'CloseRequestFcn',{#localCloseFigure,interfaceObject});
%%
% Setup the axes
axesHandle = axes('Parent',figureHandle,...
'YGrid','on',...
'YColor',[0.9725 0.9725 0.9725],...
'XGrid','on',...
'XColor',[0.9725 0.9725 0.9725],...
'Color',[0 0 0]);
xlabel(axesHandle,'Number of Samples');
ylabel(axesHandle,'Value');
%%
% Initialize the plot and hold the settings on
hold on;
plotHandle = plot(axesHandle,4,'-y','LineWidth',1);
%% Setup interface object to read chunks of data
% Set the number of bytes to read at a time
bytesToRead = 500;
%%
% Define a callback function to be executed when desired number of bytes
% are available in the input buffer
interfaceObject.BytesAvailableFcn = {#localReadAndPlot,plotHandle,bytesToRead};
interfaceObject.BytesAvailableFcnMode = 'byte';
interfaceObject.BytesAvailableFcnCount = bytesToRead;
%%
% Open the interface object
fopen(interfaceObject);
pause(3);
snapnow;
%% Implement the bytes available callback
function localReadAndPlot(interfaceObject,~,figureHandle,bytesToRead)
%%
% Read the desired number of data bytes
data = fread(interfaceObject,bytesToRead);
%%
% Update the plot
set(figureHandle,'Ydata',data);
%% Implement the close figure callback
function localCloseFigure(figureHandle,~,interfaceObject)
%%
% Clean up the interface object
fclose(interfaceObject);
delete(interfaceObject);
clear interfaceObject;
%%
% Close the figure window
delete(figureHandle);
My problem is that I have a plot in real time but I have no idea which data I am plotting. I know that the data that arrived from the iPhone are a matrix with 62 column (if I export the data from the iPhone directly I get a .csv file of 62 columns).
How can I choose with column I plot ?
Thank you very much!

Answer 1

Here would be my take on indexing the data only for the required column:
function real_time_data_stream_plotting()
% These can be very well arguments for the function
FRAME_SIZE = 62; % This many columns (each columns is one byte)
FRAME_COUNT = 500; % This much data to plot at once
DATA_COLUMN = 3 % Position of the plotted column
% Create connection
conn = tcpip('192.168.1.111', 52928);
% Set-up graphics
hf = figure( ...
'NumberTitle', 'off', ...
'Name', 'Live Data Stream Plot', ...
'Color', [0 0 0], ...
'CloseRequestFcn', {#localCloseFigure,conn} ...
);
ha = axes( ...
'Parent', hf,...
'YGrid', 'on', ...
'YColor', [0.9725 0.9725 0.9725], ...
'XGrid', 'on', ...
'XColor', [0.9725 0.9725 0.9725], ...
'Color', [0 0 0] ...
);
hold(ha, 'on');
xlabel(ha,'Number of Samples');
ylabel(ha,'Value');
hl = plot(ha, 4, '-r', 'LineWidth', 1);
% Set-up connection callback
conn.BytesAvailableFcn = {#update_plot, hl, FRAME_SIZE, FRAME_COUNT, DATA_COLUMN};
conn.BytesAvailableFcnMode = 'byte';
conn.BytesAvailableFcnCount = FRAME_SIZE * FRAME_COUNT;
% Open connection and exit
fopen(conn);
pause(3);
snapnow;
end
% -------- Local Functions --------
function update_plot(conn, ~, hl, frame_size, frame_count, data_column)
data = fread(conn, frame_count*frame_size);
data = data(data_column + frame_size*(0:frame_count-1));
set(hl, 'YData', data);
end
function clean_up_on_close(hf, ~, conn)
fclose(conn);
delete(conn);
clear conn;
delete(hf);
end
However, I don't feel comfortable posting code based on on copyrighted work...