sending over serial port

hi i am trying make a gui that will send data over serial port. my gui looks like this. it selects an copen port from the popup menu. when the connect button is pressed, it will connect. when the send button is pressed, it sends the data.

for now, the connect pushbutton works and so it will connect. but the send button will generate an error.

my code is somehow like this:

function connectbutton_Callback(hObject, eventdata, handles)
if strcmp(get(handles.connectbutton,'String'),'Connect')
      serPortn = get(handles.popupmenu1, 'Value');
    if serPortn == 1
        errordlg('Select valid COM port');
    else
        serList = get(handles.popupmenu1,'String');
        serPort = serList{serPortn};
        serConn = serial(serPort, 'TimeOut', 1, ...
            'BaudRate', str2num(get(handles.baudrate, 'String')));
        try
            fopen(serConn);
            set(handles.sendbutton, 'Enable', 'On');
            set(handles.connectbutton,'String','Disconnect')
        catch e
            errordlg(e.message);
        end
    end
else
    set(handles.sendbutton, 'Enable', 'Off');
    set(connectbutton, 'String','Connect')
    fclose(serConn);
end
guidata(hObject, handles);

function sendbutton_Callback(hObject, eventdata, handles)
fprintf(serConn, 'E:\matlab workspace\gui\image.bmp');
out = fread(serConn, comPort.BytesAvailable,'uint8');

the error here is:

Undefined function or variable 'serConn'.

Error in mygui>sendbutton_Callback (line 101) fprintf(serConn, 'E:\matlab workspace\gui\image.bmp');

Answer 1

[Walter Roberson]

http://matlab.wikia.com/wiki/FAQ#How_can_I_share_data_between_callback_functions_in_my_GUI.3F