Plotting Data Continuously From Arduino Serial

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Noa Reisner-Stehman
Noa Reisner-Stehman on 5 Apr 2017
Commented: Akash Kalghatgi on 3 Feb 2021
I am currently attempting to read in data from an alcohol sensor in Arduino. The code works with a for loop, with the data being stored as a vector.
I would like to plot this data against time, for an infinite amount of time. I have tried using an infinite while loop, but it failed to update the graph each time (no points show up).
The Code looks like this:
arduino= serial('/dev/cu.usbserial-DA01P0H8', 'BaudRate', 9600); fopen(arduino);
pause on;
x = 0; y = 1;
while 1 == 1
alcohol = fscanf(arduino, '%f');
time = x;
plot(x, alcohol);
pause(5);
x = x + 5;
y = y + 1;
end
Any help would be appreciated! Thanks :)

Answers (2)

Nick
Nick on 7 Apr 2017
Edited: Nick on 7 Apr 2017
This is an old code I had before Arduino had a support package so I'm getting data from the Arduino a different way but this will plot until you stop it.
%This is a script that will plot Arduino analogRead values in real time
%Modified from http://billwaa.wordpress.com/2013/07/10/matlab-real-time-serial-data-logger/
%The code from that site takes data from Serial
clear
clc
%User Defined Properties
a = arduino('Com13') % define the Arduino Communication port
plotTitle = 'Arduino Data Log'; % plot title
xLabel = 'Elapsed Time (s)'; % x-axis label
yLabel = 'Temperature (C)'; % y-axis label
legend1 = 'Temperature Sensor 1'
legend2 = 'Temperature Sensor 2'
legend3 = 'Temperature Sensor 3'
yMax = 40 %y Maximum Value
yMin = 0 %y minimum Value
plotGrid = 'on'; % 'off' to turn off grid
min = 0; % set y-min
max = 40; % set y-max
delay = .01; % make sure sample faster than resolution
%Define Function Variables
time = 0;
data = 0;
data1 = 0;
data2 = 0;
count = 0;
%Set up Plot
plotGraph = plot(time,data,'-r' ) % every AnalogRead needs to be on its own Plotgraph
hold on %hold on makes sure all of the channels are plotted
plotGraph1 = plot(time,data1,'-b')
plotGraph2 = plot(time, data2,'-g' )
title(plotTitle,'FontSize',15);
xlabel(xLabel,'FontSize',15);
ylabel(yLabel,'FontSize',15);
legend(legend1,legend2,legend3)
axis([yMin yMax min max]);
grid(plotGrid);
tic
while ishandle(plotGraph) %Loop when Plot is Active will run until plot is closed
dat = a.analogRead(0)* 0.48875855327; %Data from the arduino
dat1 = a.analogRead(2)* 0.48875855327;
dat2 = a.analogRead(4)* 0.48875855327;
count = count + 1;
time(count) = toc;
data(count) = dat(1);
data1(count) = dat1(1)
data2(count) = dat2(1)
%This is the magic code
%Using plot will slow down the sampling time.. At times to over 20
%seconds per sample!
set(plotGraph,'XData',time,'YData',data);
set(plotGraph1,'XData',time,'YData',data1);
set(plotGraph2,'XData',time,'YData',data2);
axis([0 time(count) min max]);
%Update the graph
pause(delay);
end
delete(a);
disp('Plot Closed and arduino object has been deleted')
  1 Comment
Jacob Schoeb
Jacob Schoeb on 6 Apr 2018
How do you get a.analogRead. It keeps having an error at that step

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Tommy Fu
Tommy Fu on 10 Jun 2019
Edited: Tommy Fu on 10 Jun 2019
Nick's program works. But when run the MATLAB program, it seems MATLAB will write something into the Arduino board to override the Arduino program in the board. I would like to consult that how I can solve this problem. Thank you!
  1 Comment
Akash Kalghatgi
Akash Kalghatgi on 3 Feb 2021
For this, you have to update the following lines
device = serialport("com9", 115200)
data = readline(device) %if your device uses serial print
%OR
data = read(device,1,"double") %if your device uses serial write

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