I am getting an error message when trying to change a color in the GUI through a script file.

I created a very simple GUI using GUIDE that contains a push button and a text box. I also created a script file that I am using to read inputs from an Arduino. What I want to happen is when I push a button that is connected to pin 8 of the Arduino I want the push button on the GUI to change colors to red. I am basically using the GUI as a user feedback, not as an input. This is my script file: (titled 'Untitled2')

delete(instrfindall)
clear b;
b = arduino('COM5');

b.pinMode(8, 'INPUT');
b.pinMode(2, 'INPUT');

x = 0;

Change; %this is the name of my GUI '.m' file

fprintf('Go');

while (x == 0)

      if (b.digitalRead(8) == 1)
          set(handles.pushbutton1,'backgroundcolor','r');
      end

      x = b.digitalRead(2);
end
fprintf('End');

here are the first lines of output I get:

Attempting connection .............
Analog & Digital I/O + Encoders + Servos (adioes.pde) sketch detected !
Arduino successfully connected !
Go

This means that the connection to the Arduino is good and the program is currently in the 'while' loop, but when I push the button connected to pin 8 I get the following error message:

Struct contents reference from a non-struct array object.

Error in Untitled2 (line 16)
        set(handles.pushbutton1,'backgroundcolor','r');

Any help would be greatly appreciated.

Thanks.

Answer 1

[Walter Roberson]

Your code does not define "handles"

IF you were using a GUI built in GUIDE, then "handles" would automatically be passed in as the third parameter of your callback function. But you are not using a function, you are using a script and it is not being called through a callback so you should not expect handles to be defined at all.

Sigh. Right after the call to Change; add the line

handles = guidata(gcf);

and you will probably get handles well defined.

[Brett Harrington]

Thank you this slight change to my code now means I dont have any error message when I push the button connected to pin 8, but it still doesn't change the color of the button on the GUI. Do you know why that might be?

[Image Analyst]

Brett, we do not have your arduino. How do we know it's even wired up correctly? And does the GUI pushbutton turn color if you issue the set() command regardless of what's happening on the arduino? Check that first before you try putting it into "ifs" based on the arduino pin states.

[Walter Roberson]

add a drawnow() after the set()

Also remember to change the color back at some point.

[Brett Harrington]

Thank you again Walter!! This does exactly what I want.