MATLAB: How to clear Arduino connection when it is a member of handles in GUI

arduinohandlesMATLABmatlab gui

I recently started building a GUI to set up a small control system based on arduino. Here is the thing. I set up my arduino in the opening function with following code

handles.board=arduino();

I thought this would be helpful since I only need to pass the handles variable. It worked pretty well. But after I close the GUI, it cant not start again due to the error below.

    MATLAB connection to Due at COM4 exists in your workspace. To create a new connection, clear the existing object

I might need to clear the arduino variable just as MATLAB arduino tutorial does. But after i close the GUI, running 'clear' or 'clear all' cannot solve the problem. Meanwhile, if I restart the GUI with the arduino line being commented, there won't be a board member in handles. So the handles is destroyed after GUI is shut down but the connection is still there. What should I do?

Best Answer

Hi Zicong,

Try clearing out the Arduino object in the CloseRequestFcn. This callback executes whenever you try to close your GUI, so you might be able to clear the connection.

Also use the following function to clear the board object.

clear aurduino_object ;

Related Solutions

MATLAB: OOP member variable “properties” access from member functions

You've made two mistakes with your code.

The first one, not specific to matlab is that static methods don't apply to to objects ofthe class but are generic to the class. So first thing is to remove the static attribute from your methods.

The second error, specific to matlab is that unlike most other languages the object the method applies to must be specified as the first argument of the function.

Therefore your method block should be:

methods
    function connectToMeter(this, Address) %I prefer calling the object this (as in C++/C#) rather than obj
        addressStr = sprintf('TCPIP0::%s::inst0::INSTR', Address);
        this.visaObj = visa('agilent', addressStr);
        fopen(this.visaObj);
    end
    function readPower(this)
         fprintf(this.visaObj, 'READ1?');
         idn = scanstr(this.visaObj);
    end
end

MATLAB: Access to class members

The Code Analyzer is a useful feature. It indicates syntax errors in the rightmost column of the editor. And it provides tooltips. Properties has the attribute GetAccess, but methods only has Access. IMO: one should try to keep the little box green at all times.

Your classes are value classes. Is that your intention? See Comparison of Handle and Value Classes

This is one way of "accessing the class members of one class to another class"

>> objcore=clcore(1,2)
objcore = 
  clcore with no properties.    % <<< private properties are not shown
>> objMec = clMec
objMec = 
  clMec with properties:
    Mecmode: []
>> objMec = objMec.access_value_of( objcore )
objMec = 
  clMec with properties:
    Mecmode: 3
>>

where

classdef clMec
    properties 
        Mecmode
    end
   methods
       function     obj = access_value_of( obj, friend )
            obj.Mecmode = friend.ws;
       end
   end
end

and

classdef clcore
    properties(GetAccess=?clMec)
       cpc
       csc 
    end
    properties(Dependent, GetAccess=?clMec)
        ws
    end
    methods  
        function    obj = clcore( arg1, arg2 )   
            obj.cpc = arg1;
            obj.csc = arg2;
        end
        function    ws = get.ws(obj)
           ws=obj.cpc+obj.csc; 
        end
    end
end

Best Answer

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MATLAB: OOP member variable “properties” access from member functions

MATLAB: Access to class members

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