How to plot in realtime properly? (from a serialport) Matlab - matlab

Question

I am reading data from a serialport using callback terminator:
configureCallback(s,"terminator",#readSerialData)
I want to plot this data in real time. So what I do is to use a global structure of arrays where the gathered data is stored in every new row. There are different arrays because I need to classify different sources of data
I use a function "createfigure" inside the #readSerialData, which plots the array of the corresponding source of incoming data.
However, this becomes extremely laggy, so this must not be the right way to do...
Also, in the graphs I want to see all the arrays plotted in once. But the result is that it only plots the last received array on top of the other plots. So it accumulates lines on top of each other, making the axes illegible
function createfigure2(source,X1,Y1)
% X1: vector of x data
% Y1: vector of y data
% Auto-generated by MATLAB on 21-Jan-2021 13:54:53
% Create figure
figure1 = figure(1);
hold on;
% Create axes
axes1 = axes('Parent',figure1,...
'Position',[0.109498680738786 0.69811320754717 0.800791556728232 0.273584905660377]);
hold(axes1,'on');
% Create plot
plot(X1,Y1,'DisplayName',source,'Parent',axes1,'Marker','*','LineWidth',0.01,...
'LineStyle',':');
end

Answer 1

You can create a plot object (parameter returned when calling the plot function) and send it to the callback itself by setting it as a parameter of "BytesAvailableFcn". Then update the plot directly inside the callback.
function mainFunction()
figure1 = figure();
axes1 = axes('Parent',figure1,...
'Position',[0.109498680738786 0.69811320754717 0.800791556728232 0.273584905660377]);
numParams = 4;
plotObjects = cell(1,numParams);
plotObjects{1} = plot(nan,nan,'r-','parent',axes1);
hold(axes1, 'on');
plotObjects{2} = plot(nan,nan,'g-','parent',axes1);
plotObjects{3} = plot(nan,nan,'b-','parent',axes1);
plotObjects{4} = plot(nan,nan,'k-','parent',axes1);
hold(axes1, 'off');
sp = openSerialPort('COM9', plotObjects);
...
end
function sp = openSerialPort(portName, plotObjects)
% intialize your com port here
sp = serial(portName);
sp.BaudRate = 9600;
...
sp.BytesAvailableFcn = {#plotMyData, plotObjects}
end
function plotMyData(sp, ~, plotObjects)
% read the data from the serial port...
[dataVectX, dataVectY] = get_data_from_serial...
% This considers that dataVectX and Y contains the readings of 4...
% different sensors where dataVectX(1) is the first sensor, dataVectX(2) is...
% the second sensor, and so one.
% update data
for paramID = 1:4
plotObjects{paramID}.XData = dataVectX(paramID);
plotObjects{paramID}.YData = dataVectY(paramID);
end
% if you wanted to append the data instead of replacing it you can either use
% plotObjects{paramID}.XData = [plotObjects{paramID}.XData, newXVector]; % use this if x is a vector
% plotObjects{paramID}.YData = [plotObjects{paramID}.YData, newYVector];
% or
% plotObjects{paramID}.XData(end+1) = dataVectX(paramID); % use this if x is a single value
% plotObjects{paramID}.YData(end+1) = dataVectY(paramID);
drawnow();
end