这个matlab程序错在什么地方了

这个matlab程序错在什么地方了
% --- Executes on button press in pushbutton1.
function pushbutton1_Callback(hObject,eventdata,handles)
% hObject handle to pushbutton1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
set(handles.text1,'String',0);
guidata(hObject,handles);
global obj;
obj=serial('com1','baudrate',9600,'parity','none','databits',8,'stopbits',1);% obj
%scom1.BaudRate = 9600;
obj.InputBufferSize = 1024;
obj.OutputBufferSize = 1024;
obj.BytesAvailableFcnMode='byte';
obj.BytesAvailableFcn={@EveBytesAvailableFcn,handles};%
obj.BytesAvailableFcnCount=10; %
fopen(obj);
t1=now;
fwrite(obj,255);
%delete('scom1');
%clear scom1;
function EveBytesAvailableFcn(hObject,eventdata,handles)
global obj;
fread(obj,1);%
t2=now;
t=86400*(t2-t1);
set(handles.text2,'String',t);
guidata(hObject,handles);