What is causing error " Error evaluating 'StartFcn' callback of block_diagram 'MotorModel'. Undefined function or variable 'localAddE​ventListen​er'."

i started trying to work with GUI and simmulink. I created a simulink model of a motor and modified a piece of code found online to give me the following code:

        function callsim

        %define the model name
        ModelName = 'MotorModel';
        %open the simulink model
        load_system(ModelName);
        % Simulink may optimise your model by integrating all your blocks. To
        % prevent this, you need to disable the Block Reduction in the Optimisation
        % settings.
        set_param(ModelName,'BlockReduction','off');
        %call the eventlistner 
        set_param(ModelName,'StartFcn','localAddEventListener');
        % set the stop time to inf
        set_param(ModelName,'StopTime','inf');
        % set the simulation mode to normal
        set_param(ModelName,'SimulationMode','normal');
        % Set a listener on the Gain block in the model's StartFcn
        set_param(ModelName,'StartFcn','localAddEventListener');
        % start the model
        set_param(ModelName,'SimulationCommand','start');
        %create a line to plot coordinates
        global ph;
        ph = line(0,0);
        % When simulation starts, Simulink will call this function in order to
        % register the event listener to the block 'SineWave'. The function
        % localEventListener will execute everytime after the block 'SineWave' has
        % returned its output.
        eventhandle;
        function eventhandle = localAddEventListener

                 eventhandle = add_exec_event_listener('MotorModel/Motor', ...
                                                'PostOutputs', @localEventListener);
        end    
        % The function to be called when event is registered.

        function localEventListener(block, eventdata)

            disp('Event has occured!')
            %global ph;

            % Gets the time and output value
            simTime = block.CurrentTime;
            simData = block.OutputPort(1).Data;

            % Gets handles to the point coordinates
            xData = get(ph,'XData');
            yData = get(ph,'YData');

            % Displaying only the latest n-points
            n = 200;

            if length(xData) <= n
                xData = [xData simTime];
                yData = [yData simData];
            else
                xData = [xData(2:end) simTime];
                yData = [yData(2:end) simData];
            end

            % Update point coordinates

            set(ph,...
                'XData',xData,...
                'YData',yData);

            % The axes limits need to change as you scroll
            samplingtime = .01;

            %Sampling time of block 'SineWave'
            offset = samplingtime*n;
            xLim = [max(0,simTime-offset) max(offset,simTime)];
            set(gca,'Xlim',xLim);
            drawnow;
        end

    end

i am not too sure why i get the error and was hoping i could have someone help me understand where i am going wrong here

Answer 1

[Walter Roberson]

The line

set_param(ModelName,'StartFcn','localAddEventListener');

needs to be changed to

set_param(ModelName,'StartFcn',@localAddEventListener);

However, notice the line that currently reads

eventhandle;

right before the line

function eventhandle = localAddEventListener

That line right before "function" will almost certainly need to be commented out:

%eventhandle;

[africanwizz96]

Thanks for your response, i made the suggested changes and now matlab crashes each time i execute the section of code, could it be a problem with my model?

[Walter Roberson]

Do you even receive the Event has occured! message? If so more than once?

[africanwizz96]

nope, it doesn't get that far

[Walter Roberson]

Comment out the

set_param(ModelName,'StartFcn','localAddEventListener');

and see if it runs, to isolate whether the problem is in setting up the listener.

And inside localAddEventListener add a display of a message before and after it sets up the listener, to see if it is that that is failing.

[africanwizz96]

Hi

when i use the format you suggested:

   set_param(ModelName,'StartFcn',@localAddEventListener);

matlab still crashes, commenting it out gives the original error message i was getting.Using the code below.

        set_param(ModelName,'BlockReduction','off');
        %call the eventlistner 
        set_param(ModelName,'StartFcn','localAddEventListener');
        % set the stop time to inf
        set_param(ModelName,'StopTime','inf');
        % set the simulation mode to normal
        set_param(ModelName,'SimulationMode','normal');
        % start the model
        set_param(ModelName,'SimulationCommand','start');
        %create a line to plot coordinates
        global ph;
        ph = line(0,0);
        % When simulation starts, Simulink will call this function in order to
        % register the event listener to the block 'SineWave'. The function
        % localEventListener will execute everytime after the block 'SineWave' has
        % returned its output.

        disp('im goin in');
        function eventhandle = localAddEventListener

                 disp('ive come this far');

                 eventhandle = add_exec_event_listener('MotorModel/Motor', ...
                                                'PostOutputs', @localEventListener);

                 disp('ive reached your end');
        end

it only prints out "im goin in" so i think it is a problem in setting up the listener.

Thanks for your help

[Walter Roberson]

The simplest possibility would be that MotorModel/Motor does not exist. Try putting a try/catch around the add_exec_event_listener and displaying the content of the exception structure.

[africanwizz96]

Ok thanks alot, will keep working on it