MATLAB gui plots the data in a new figure instead of specified axes

I am developing a MATLAB GUI which is supposed to get serial data and plot it after processing. I use bytesavailabefcn a callback function which is executed when a pre-specified number of bytes (bytesavailablefcncount) become available.

The code works well and gets the serial data. But when using plotyy to plot the data it opens a new figure and plots the data on it rather than plotting it in the axes which is drawn in the GUI and is tagged as axes1. I use axes(handles.axes1) to assign it to axes1, but the problem still exists. I am using MATLAB 2007b and can not switch to newer versions.

here is a shortened version of my code:

function pushbutton1_Callback(hObject, eventdata, handles)
       ...
       ...
       global s;
       s = serial('COM4');       % Create a serial object 
       s.baudrate = 9600;
       s.BytesAvailableFcnMode = 'byte';
       s.BytesAvailableFcnCount = 21;
       s.BytesAvailableFcn = {@instrcallback,gcf};
       fopen(s);
       ...
       ...
end



function instrcallback(hObject, eventdata,fignum)
       ...
       ...
       handles = guidata(fignum);
       global s;
       axes(handles.axes1);
       [ax,h1,h2] = plotyy(G1,m1,G1,m2);
       set(ax(1),'YLim',[(y1offset -zoom1-10), (y1offset +zoom1+10)]);
       set(ax(2),'YLim',[(y2offset -zoom2-10), (y2offset +zoom2+10)]);
       set(ax(1),'BOX' ,'off');
       set(ax(1),'Xgrid','on');
       set(ax(2),'Ygrid','on');  
       drawnow;
       ...
       ...
end

The correct syntax is: [ax,h1,h2] = plotyy(handles.axes1, G1,m1,G1,m2);

Recommended updates:

• In pushbutton1_Callback:
  Replace {@instrcallback,gcf}; with {@instrcallback, handles};:

  function pushbutton1_Callback(hObject, eventdata, handles)
  ...
  s.BytesAvailableFcn = {@instrcallback, handles};
  

• In instrcallback: use the following syntax:

  function instrcallback(hObject, eventdata, handles)
  [ax,h1,h2] = plotyy(handles.axes1, G1,m1,G1,m2);
  ...
  

According to documentation:

axes(cax) makes the axes or chart specified by cax the current axes and brings the parent figure into focus.

I can't figure out why a new figure is opened.

---

Here is a code that reproduce the problem using a Timer instead of serial:

function pushbutton1_Callback(hObject, eventdata, handles)
t = timer;
handles.t = t;
guidata(hObject, handles)
t.TimerFcn = {@instrcallback,handles};
t.ExecutionMode = 'fixedRate';
t.StartDelay = 1;
t.Period = 1;
start(t)


function instrcallback(hObject, eventdata, handles)
axes(handles.axes1);
plot(sin(-3:0.1:3 + rand(1)));

The problem repeats using MATLAB R2019a in Windows 10.