Read continuous reading from Potentiometer and plot graph issues

Hi everyone, I have an issue that i still can't figure it out and really need helps from experts. I try to read continuous reading from 2 potentiometers and plotted it in 1 figure. i tried to use animatedplot, however, i still don't find the best solutions for it. Thus, i stick to this easy (for me) but problematic code as below. The problem is, it runs very slow and after run about few minutes, the Matlab become crash. It give me "Matlab experienced unexpected error" for several times already and i think the code might be the cause. Can someone help and guide me,please?

clear all
clc

opengl('save', 'software');

a = arduino('COM3','Uno','Libraries','Servo'); %only needed if arduino not connected

NumberOfReadings = 100;            %Set number of readings
analog1 = zeros(1,NumberOfReadings); %holds voltage reads
analog2 = zeros(1,NumberOfReadings); %holds voltage reads

while 1==1                          % continually run
    for index = 1:NumberOfReadings      % run values 2 through 99
        analog1(index)  = readVoltage(a,'A3'); % Servo A
        analog2(index)  = readVoltage(a,'A1'); % Servo B
        
        AllValues_A = analog1(index)+AllValues_A; %adds all values for test
        AllValues_B = analog2(index)+AllValues_B; %
        
        pause (.0005); %slow down read speed
        
        %% VOLTAGE PLOT  
        subplot (1,2,1)
        plot(analog1) %plot values
        hold on
        plot(analog2)
        legend('Potentiometer A','Potentiometer B')
        hold off
        
        ylim([0 5]); %set y limits of plot
        ylabel('Voltage'); %label Y axis
  
        %% DISPLAY VALUE IN BIT
        %AnalogRead1 = analog1(index)   * (1023 / 5); 
        %AnalogRead2 = analog2(index) * (1023 / 5);
        
        %fprintf('\n Potentiometer: A= %.2f  B= %.2f ',AnalogRead1,AnalogRead2);
      
        %% CHANGE OF ANGULAR DISPLACEMENT PLOT      
        
        AnalogRead_Hip  = analog1(index) * (360 / 5); 
        AnalogRead_Knee = analog2(index) * (360 / 5);  
        
        subplot (1,2,2)
        plot(index,AnalogRead_Hip,'Color','b','LineWidth',2);
        hold on
        plot(index,AnalogRead_Knee,'Color','k','LineWidth',2);
        legend('Hip Angle','Knee Angle')
        hold off
    
        ylim([0 360]); %set y limits of plot
        xlim([0 100]);
        ylabel('Change of Angular Displacement'); %label Y axis
        fprintf('\n Reading: A= %.2f  B= %.2f ',AnalogRead_Hip,AnalogRead_Knee);
    end
end % end while loop

[Rohan Kale]

Hi Aliff,

A few suggestions -

a) You can use animatedline API to plot the points. With this, the points can be appended to the plot inside the loop.

Consider creating the animatedline handles and plot axes, legends, etc. outside the loop beforehand.

Refer to the documentation for more information on the API

https://www.mathworks.com/help/matlab/ref/animatedline.html

b) You could get rid off the while(1) as the number of points to be read are predetermined in your code.

Hope it helps.

[aliff saad]

Hi Rohan, thanks for the reply.

For your first suggestion, i already tried to use the animatedline plot based on the examples and questions asked by others in Mathworks. However, i still can't find the issue. I attached together the code that i have plotted using animatedline.

clear all

clc

a = arduino('COM3','Uno','Libraries','Servo'); %only needed if arduino not connected

NumberOfReadings = 100; %Set number of readings

analog1 = zeros(1,NumberOfReadings); %holds voltage reads

analog2 = zeros(1,NumberOfReadings); %holds voltage reads

index = zeros(1,NumberOfReadings);

figure(1)

hplot1 = animatedline(index(1),analog1(1),'Color','b','LineWidth',2);

hold on

hplot2 = animatedline(index(1),analog2(1),'Color','m','LineWidth',2);

%% VOLTAGE PLOT

legend('Potentiometer A','Potentiometer B')

ylim([0 5]);xlim([0 NumberOfReadings]); %set y limits of plot

ylabel('Voltage'); %label Y axis

while 1==1

for index = 2:NumberOfReadings % run values 2 through 99

analog1(index) = readVoltage(a,'A0'); % Servo A

analog2(index) = readVoltage(a,'A1'); % Servo B

clearpoints(hplot1)

clearpoints(hplot2)

addpoints(hplot1,index,analog1(index));

addpoints(hplot2,index,analog2(index));

drawnow limitrate

pause(0.005)

end

end

for the second suggestion, i will try to remove it and find better solutions to make the code continuous. Thanks for the suggestions, im really appreciate it

[aliff saad]

I think, the issue might come from repeating "readVoltage" that occur in every iteration. Moreover, the Matlab needs to read two values at the same time.