How to read multiple sensors through the serial.

Hi guys

I hope you can help me.

I have connected 4 force sensors to an Arduino, and I´m sending the data to the serial port simultanious – no problems so far.

Now I would like Matlab to read the serial and plot 4 graphs, 1 from each sensor.

The data in the serial are organized in 8 coloums with a description and the value for each sensor.

My problem is, that I dont know how to seperate the serial so each of the four dataset is placed in its own variable so I afterwards can make the plots.

This is my code:

clear all
clc

arduino=serial('COM4','BaudRate',9600);

fopen(arduino);

x=linspace(1,100);

for i=1:length(x);
y(i)=fscanf(arduino,'%f'); 
end
fclose(arduino)

This very basic code only reads the first "coloum" in the serial - how do I add the other coloum, so I can get that data as well?

I appreciate any help :)

Best regards Kasper

[Nazrin Zaini]

have you found the solution for this problem?i really like to know what is the solution.do you mind to share with me? really glad if you can share it :)

Answer 1

[Walter Roberson]

numcols = 8;
y = zeros(length(x), numcols);

for k = 1 : numcols
  for i=1:length(x);
    y(i, k)=fscanf(arduino,'%f'); 
  end
end

plot(y);

Note: this depends upon all of the data for one sensor being consecutive on the serial port, but the way you describe it you have one data value for each sensor before proceeding to the next data value for the first sensor, and so on. I think it should probably be more like,

numcols = 8;
y = zeros(length(x), numcols);

fmt = repmat('%f', 1, numcols);

for i=1:length(x);
  y(i, :) = fscanf(arduino, fmt); 
end

plot(y);

[Kasper]

Hi Walter and thanks for your quick reply.

I have tried both. And now I get 8 coloums, but only the first coloum is being filled with sensor data from the first sensor, so I need the remaining 3 sensors.

When I look at the serial in my Arduino, it looks like this:

 Heel  0.0000 Metatars 1 0.5258 Svang 0.4290 Calcanus 0.0000
 Heel  0.0258 Metatars 1 1.3258 Svang 0.8871 Calcanus 0.0774
 Heel  0.1032 Metatars 1 1.5677 Svang 1.2226 Calcanus 0.0677
 Heel  0.1710 Metatars 1 1.4452 Svang 1.0355 Calcanus 0.0871
 Heel  0.6484 Metatars 1 1.3161 Svang 1.0677 Calcanus 0.1452
 Heel  1.2548 Metatars 1 1.1677 Svang 1.0839 Calcanus 0.0968

I would like to read coloum 2,4,6 and 8, and put them in four variables so I later can plot them with time x.

Any ideas?

Best regards Kasper

Answer 2

[Kasper]

Finally I have figured out the code. If anybody should find this thread, and have the same problem, here is the code which worked:

clear all
clc

arduino=serial('COM4','BaudRate',9600);

fopen(arduino); 

   x=linspace(1,100); % der optages 100 samples

     numcols = 1; %der laves en kollonne med data
     y = {}; %alt data smides i y
  for i=1:length(x);    
    data =fscanf(arduino,'%f'); % '%f' gør at det er decimaler
       IncomingString = char(data); % den indkomne data laves om til karaterer
       IncomingString = regexp(IncomingString, '\s*', 'split'); %dataen splittes op med mellemrummer og i kolonner.
         Heel(i,1)= IncomingString(1,3); %#ok<SAGROW> % jeg har suppressed en fejl %læser i kolonne 3
         Metatars(i,1)= IncomingString(1,5); %læser i kolonne 5
         Svang(i,1)= IncomingString(1,7); 
         Calcaneus(i,1)= IncomingString(1,9);

end

    if true
      % code
    end
  fclose(arduino);

PlotHeel = str2double(Heel); %Omdanner data som er på cell array til double data
figure(1)
plot(PlotHeel);
title('Heel'); xlabel('Samples'); ylabel('Volt');

PlotMetatars = str2double(Metatars); %Omdanner data som er på cell array til double data
figure(2)
plot(PlotMetatars);
title('Metatars'); xlabel('Samples'); ylabel('Volt');

PlotSvang = str2double(Svang); %Omdanner data som er på cell array til double data
figure(3)
plot(PlotSvang);
title('Svang'); xlabel('Samples'); ylabel('Volt');

PlotCalcaneus = str2double(Calcaneus); %Omdanner data som er på cell array til double data
figure(4)
plot(PlotCalcaneus);
title('Calcaneus'); xlabel('Samples'); ylabel('Volt');

%Written by Kasper Stentz

[Nazrin Zaini]

how about the arduino code, i am working out using your matlab code and try to figure out how to make columns for each sensor data in arduino, but not succesfull.

[chfakht chfakht]

i'm getting this error : Warning: Unsuccessful read: Matching failure in format. Index exceeds matrix dimensions.

Error in Serial2 (line 12) Heel(i,1)= IncomingString(1,3); %#ok<SAGROW> % jeg har suppressed en fejl %læser i kolonne 3

Answer 3

[Alvaro Anillo]

It would be great to see how works the arduino code because I don't see how it is sended the data, with the original code I can handle the inferface between serial port and matlab.

I need to read just two variables from my arduino code to plot time vs voltage so must be very easy but I'm just stopped

void loop(){
  //read
  Serial.println(analogRead(A0));
  Serial.println(micros());
}

Thanks in advance

[Andhika Nagami]

did you find the arduino code?

[Rehan Qasim]

??