Motor control using keyboard, Matlab and Arduino+shield

My goal is to control a DC motor by pressing pc keyboard's keys. I'm using Arduino+motor shield (legacy Adafruit Motor Shield v1). I've already partially succeeded by using the following code on Matlab:

fig_h = figure;
set(fig_h,'KeyPressFcn', @key_pressed_fcn);

function key_pressed_fcn(fig_obj,eventDat)
   a = arduino('COM3')
   c = get(fig_obj, 'CurrentKey');
   if c == 'e'
            motorSpeed(a,2,100);      
            motorRun(a,2,'forward');
            pause(2);
            motorSpeed(a,2,0); 
   end
end

This code runs the motor for a couple of seconds after pressing the 'e' key. The problem is that Matlab connects to Arduino every time the key 'e' is pressed, even though the code runs without interruptions. What I want is for Matlab to connect to Arduino once at the beginning and then run the motor every time the key is pressed without reconnecting again.

If I try to move the line that connects Matlab to Arduino, like this:

a = arduino('COM3')
fig_h = figure;
set(fig_h,'KeyPressFcn', @key_pressed_fcn);

function key_pressed_fcn(fig_obj,eventDat)
   c = get(fig_obj, 'CurrentKey');
   if c == 'e'
            motorSpeed(a,2,100);      
            motorRun(a,2,'forward');
            pause(2);
            motorSpeed(a,2,0); 
   end
end

I think I could avoid needless reconnecting. But running this code results in error message: " Undefined function or variable 'a'.".

Any ideas how to solve this?

[Saurav Shenoy]

try making it an input to the function but still define it outside the function!