Sending values from Matlab to arduino using serial communication

I want to send numeric value from matlab to arduino but code is not working. Matlab code is as:

    doi = 3 ;
arduino=serial('COM5','BaudRate',9600); % create serial communication object 
fopen(arduino); % initiate arduino communication
fprintf(arduino, '%s', char(doi)); % send answer variable content to arduino
fclose(arduino);

Arduino code is as:

    int solenoidPin = 13; //This is the output pin on the Arduino
int doi;
void setup()
{
  Serial.begin(9600);
  //pinMode(13, OUTPUT);
  pinMode(solenoidPin, OUTPUT); //Sets that pin as an output
}
void loop()
{

if(Serial.available()>0)
{

    doi = Serial.read();
    //Serial.println(doi);
    //Serial.println("\n");
    //doi = doi - 48;
   if (doi == 1)
   {
    //Serial.println(1);
    digitalWrite(solenoidPin, HIGH); //Switch Solenoid ON
    delay(1000); //Wait .15 Second
     digitalWrite(solenoidPin, LOW);
    }
  else if (doi == 2)
    {
     //Serial.println(2);
    digitalWrite(solenoidPin, HIGH); //Switch Solenoid OFF
    delay(2000); //Wait .165 Second
    digitalWrite(solenoidPin, LOW);
    }
  else 
    {
      //Serial.println(3);
      digitalWrite(solenoidPin, HIGH); //Switch Solenoid OFF
      delay(3000); //Wait .180 Second
      digitalWrite(solenoidPin, LOW);
    }

}
}

I used str2num(doi) also instead of fprintf(arduino, '%s', char(doi)) but no output.

Please give suggestion to correct this.

Thanks.

[Walter Roberson]

I would probably use

fwrite(arduino, uint8(doi));

[Naseeb Gill]

Thanks Sir for your response. But the problem is when I used

fopen(arduino)

matlab set up a communication with arduino and this process take some time like 2 seconds. So, if I used

pause(2)

after fopen(arduino), code works well. But the real problem for me here is that my doi value changes every time and I cannot used fopen(arduino) every time as it takes much time. Actually, I'm using Matlab GUI in which doi value is input through edit text box and then this value send to arduino and arduino code run according to send value. What I'm thinking is to avoid fopen(arduino) repeatedly, I can open it once by pushbutton and then send doi values to it and arduino code work as coded. To close arduino, I can used fclose(arduino)_in other pushbutton. But what the problem is I do not know how to use _fopen(arduino) command between functions in GUI? Can you please help me to solve this? Thanks.

[ahmed elshawadfy]

how do you know that it takes 2 sec to open?

[Sravani Vanama]

how to print the values send from matlab to arduino??

[Walter Roberson]

There are a few possibilities for display:

• you can send the values to some kind of display such as an LCD display; https://www.arduino.cc/en/Tutorial/HelloWorld
• you can send the values back to MATLAB and have MATLAB display them
• if you use a different connection method between MATLAB and arduino, so that the communications between MATLAB and arduino is not through the serial port monitor, then you can send the values to the serial port and use some kind of monitor system on there.
• You can use a serial port (or USB port) monitor on the MATLAB host side to see what is getting sent. https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/capture-and-view-ing-usb-traces-with-microsoft-message-analyzer- . Or see https://freeusbanalyzer.com/ which permits short monitoring for free (and presumably there is a paid version.)

Answer 1

[Walter Roberson]

"But what the problem is I do not know how to use _fopen(arduino) command between functions in GUI?"

fopen once and save the object somewhere so that you do not need to fopen again.

http://matlab.wikia.com/wiki/FAQ#How_can_I_share_data_between_callback_functions_in_my_GUI.28s.29.3F

You could have a look at https://www.mathworks.com/matlabcentral/fileexchange/26371-simple-gui-for-serial-port-communication to see how they set up communications.

[Naseeb Gill]

I already tried handles as you suggested as below:

function varargout = exam(varargin)
  gui_Singleton = 1;
  gui_State = struct('gui_Name',       mfilename, ...
                     'gui_Singleton',  gui_Singleton, ...
                     'gui_OpeningFcn', @exam_OpeningFcn, ...
                     'gui_OutputFcn',  @exam_OutputFcn, ...
                     'gui_LayoutFcn',  [] , ...
                     'gui_Callback',   []);
  if nargin && ischar(varargin{1})
      gui_State.gui_Callback = str2func(varargin{1});
  end

    if nargout
        [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
    else
        gui_mainfcn(gui_State, varargin{:});
    end

    % End initialization code - DO NOT EDIT

    function exam_OpeningFcn(hObject, eventdata, handles, varargin)

    handles.output = hObject;

    % Update handles structure
    guidata(hObject, handles);

    % --- Outputs from this function are returned to the command line.
    function varargout = exam_OutputFcn(hObject, eventdata, handles) 

    varargout{1} = handles.output;

    function edit1_Callback(hObject, eventdata, handles)

    % --- Executes during object creation, after setting all properties.
    function edit1_CreateFcn(hObject, eventdata, handles)

    if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
        set(hObject,'BackgroundColor','white');
    end

    % --- Executes on button press in pushbutton1. 
  % pushbutton to create serial communication between matlab and arduino

function pushbutton1_Callback(hObject, eventdata, handles)
   arduino=serial('COM5','BaudRate',9600); % create serial communication object on port COM4
   fopen(arduino); % initiate arduino communication
   pause(2);
   handles.arduino = arduino;
  guidata(hObject,handles);

    % --- Executes on button press in pushbutton2.
    % After enter value in edit box press pushutton to send data to arduino

function pushbutton2_Callback(hObject, eventdata, handles)
  ard = handles.arduino;
  number = str2num(char(get(handles.edit1,'String')));
  fprintf(ard, '%i', number); 
  guidata(hObject,handles);

    % --- Executes on button press in pushbutton3. 
    % to clear the port and close arduino communication

function pushbutton3_Callback(hObject, eventdata, handles)

    fclose(handles.arduino);
    delete(instrfind({'Port'},{'COM5'}));
    guidata(hObject,handles);

But arduino is not working. It just blink once when I gave input through edit box. And it is not showing any error too. Can you suggest me the solution by seeing above matlab GUI code. Thanks.

Answer 2

[Rouis Jihene]

Hello, i tried the code but i don't get the value (doi) in arduino ! why? please help

[Walter Roberson]

On the arduino side, you are probably trying to read the data as text instead of as binary. The replacement for

fprintf(arduino, '%s', char(doi)); % send answer variable content to arduino

should be

fprintf(arduino, '%d\n', doi); % send answer variable content to arduino

[Rouis Jihene]

Hello Mr Walter Roberson, even i use the instruction that you told me but i doesn't work ! please help

[Walter Roberson]

Sorry, I do not have an arduino to test with.

Answer 3

[Azrg]

The thing you want to send has to be in a while loop like

while true

fprint(something);

end

Because Matlab has to keep trying to send the information until Arduino receives it.