Arduino Programming using MATLAB, 1st Edition (2015)

8. Measuring and Plotting Sensor Data in Real-Time

In this chapter I'm going to explain how to read data from sensor devices and plot it on graph in real-time.

8.1 Getting Started

This section has an objective to show how to work with a real-time on measurement. We read data from sensor devices and display it on graph.

Let's start!.

8.2 Wiring

We use the same wiring from section 5.2

8.3 Writing a Program

Now you run MATLAB and write these scripts.

function [] = sensing()

board = arduino();

disp('press Ctr-C to exit');

h = figure(1);

finishup = onCleanup(@() exitprogram(board,h));

PCF8591 = '0x48';

PCF8591_ADC_CH0 = '40'; % thermistor

PCF8591_ADC_CH1 = '41'; % photo-voltaic

PCF8591_ADC_CH3 = '43'; % potentiometer

i2c = i2cdev(board,PCF8591);

hLine1 = line(nan, nan, 'Color','red');

hLine2 = line(nan, nan, 'Color', 'blue');

hLine3 = line(nan, nan, 'Color', 'black');

i = 0;

while1

thermistor = read_adc(i2c,hex2dec(PCF8591_ADC_CH0));

pause(0.5);

photo = read_adc(i2c,hex2dec(PCF8591_ADC_CH1));

pause(0.5);

potentiometer = read_adc(i2c,hex2dec(PCF8591_ADC_CH3));

pause(0.5);

x1 = get(hLine1, 'XData');

y1 = get(hLine1, 'YData');

x2 = get(hLine2, 'XData');

y2 = get(hLine2, 'YData');

x3 = get(hLine3, 'XData');

y3 = get(hLine3, 'YData');

x1 = [x1 i];

y1 = [y1 thermistor];

x2 = [x2 i];

y2 = [y2 photo];

x3 = [x3 i];

y3 = [y3 potentiometer];

set(hLine1, 'XData', x1, 'YData', y1);

set(hLine2, 'XData', x2, 'YData', y2);

set(hLine3, 'XData', x3, 'YData', y3);

i = i + 1;

pause(1);

end

end

function adc = read_adc(dev,config)

write(dev,config);

read(dev, 1);

out = read(dev, 1);

adc = out;

end

functionexitprogram(b,h)

clear b;

close(h);

disp('program has exit');

end

Save the program into a file, called sensing.m.

Basically, the program is similar to program from section 5.4. After read sensor data, we display it using line object from MATLAB.

8.4 Testing

You can run the program by typing this command.

>> sensing

You should see sensor data on Figure.