How to read multiple sensors through the serial.

Hi guys

I hope you can help me.

I have connected 3 sensors to an Arduino, and I´m sending the data to the serial port simultaniously – no problems so far.

Now I would like Matlab to read the serial and plot 3 graphs, 1 from each sensor.

My problem is, that I dont know how to seperate the serial so each of the 3 dataset is placed in its own variable so I afterwards can make the plots.

This is my code:

obj = serial('COM17'); %creating the object

set(obj,'BaudRate',9600) %setting baudrate

fopen(obj); %open port

set(obj,'terminator','cr') %providing the terminator
pressure1=0; % a variable for y axis

time1=now; % time is in x axis

while 2>1
    time2=now;

      x=[time1 time2];

     pressure2 = fscanf(obj) ;
     pressure=[pressure1 pressure2];

      datetick('x','HH:MM') %change the axis

      pause(0.5);

      pressure1=pressure2;

      time1=time2;
  end

[Geoff Hayes]

raki - does the data from all three sensors go through the same serial port? If so, can you tag the data that each is sending out to that you know which sensor is sending which piece of data?

[raki]

Sir, the code for arduino is shown below. How can i plot these 3 sensor values in 3 different axes created in matlab guide.

    unsigned int pres; 
    unsigned int temp; 
    unsigned int fluidrate;

    void setup()
    {
    Serial.begin(9600);
    }
    void loop()
    {
    pres = analogRead(0);
    temp = analogRead(1);
    fluidrate =  analogRead(2);
    Serial.println(pres);
    Serial.println(temp);
    Serial.println(fluidrate);
    }

[Geoff Hayes]

Can you tag the data from this sensor? I have no experience with Arduino so can only offer suggestions. Are there alternatives to Serial.println?

[raki]

Sir, i modified the code using the link http://www.mathworks.com/matlabcentral/answers/121378-how-to-read-multiple-sensors-through-the-serial

arduino code is

     unsigned int pres; 
     unsigned int temp; 
     unsigned int fluidrate;
     void setup()
    {
    Serial.begin(9600);
    }
    void loop()
    {
    pres = analogRead(0);
    temp = analogRead(1);
    fluidrate =  analogRead(2);
    Serial.print(pres);
    Serial.print("\t");
    Serial.print(temp);
    Serial.print("\t");
    Serial.print(fluidrate);
    Serial.print("\n");
    delay(1000);
   }

The data in serial monitor of arduino is

   257    7  14
   273     23  46
   327    77  154
   340    90  180
   345    95  190
   352    102  204

Matlab code is

   clear all
   clc
   arduino=serial('COM8','BaudRate',9600);
   fopen(arduino); 
     x=linspace(1,100);
     numcols = 1; 
     y = {};
     for i=1:length(x);    
     data =fscanf(arduino,'%f'); 
         IncomingString = char(data);
         IncomingString = regexp(IncomingString, '\s*', 'split');
         pres(i,1)= IncomingString(1,1); 
         temp(i,1)= IncomingString(1,2); 
         fluidrate(i,1)= IncomingString(1,3); 
     end
   fclose(arduino);
   Plotpres = str2double(pres);
   figure(1)
   plot(Plotpres);
   title('pressure'); xlabel('Samples'); ylabel('pres in bar');
   Plottemp = str2double(temp); 
   figure(2)
   plot(Plottemp);
   title('temperature'); xlabel('Samples'); ylabel('temp in C');
   Plotfluidrate = str2double(fluidrate); 
   figure(3)
   plot(Plotfluidrate);
   title('fluidrate'); xlabel('Samples'); ylabel('fluidrate in l/min');

I am getting error ??? Error using ==> regexp The first argument (STRING) must be a one-dimensional array of char or cell arrays of strings.

Error in ==> monitorsystem at 11 IncomingString = regexp(IncomingString, '\s*', 'split');

Please help me to get the output

[Geoff Hayes]

Raki - the error messages seems very clear. regexp is expecting a one-dimensional array of characters and yet it is probably getting something different. Put a breakpoint at this line, run your code, and when the debugger pauses at this line check to see what the IncomingString looks like.