You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: Graphical_user_interface.m
    path of file: ./repos/Ground-station-and-simulator-for-Unmanned-aerial-vehicle/Matlab_source_code
    
    the code of the file until where you have to start completion: function start_GUI()
h=waitbar(0.1,'Inisialisation'); 
global nbr_points_trajectory %variable qui contient le nombre de points dans le trajet
global Html_path %variable qui contient le chemin de la page html a afficher
global browser %variable d'affichage du navigateur
global temporisateur_serial temporisateur_simulator %variable du temporisateur de la lecture 
global test_acquisition_mode %variable pour specifier le mode d'acquisition(serial=true/simulator=false)
global test_debut_acquisition %variable qui contient l'etat de l'acquisition (true=started/false=not started)
%variables acquises a partir des capteurs ou du simulateur
global yaw_simulink pitch_simulink roll_simulink heading_simulink  
global Airspeed_simulink vertical_speed_simulink RPM_simulink
global temperature_simulink pressure_simulink Altitude_simulink
%Inisialisation des variables
test_acquisi
    
function Acquisition_mode_Serial (hObject, varargin)
global temporisateur_serial temporisateur_simulator test_acquisition_mode test_debut_acquisition
test_acquisition_mode=true;
 try
 set_param('simulator_model','simulationcommand','stop');    
 set_param('simulator_model/VR_Acquisition_Simulateur','value','0');
 catch  
 end
 if test_debut_acquisition
 try
 test_debut_acquisition=false;
 stop(temporisateur_simulator);
 start(temporisateur_serial)
 test_debut_acquisition=true;
 set_param('VR_acquisition_serial','simulationcommand','start');
 catch
 end
 end
         
end
%%%
function Acquisition_mode_Simulator (hObject, varargin)
global temporisateur_serial temporisateur_simulator test_acquisition_mode test_debut_acquisition
test_acquisition_mode=false;
try
 set_param('VR_acquisition_serial','simulationcommand','stop');
 
 catch  
end
 if test_debut_acquisition
 try
 test_debut_acquisition=false;
 stop(temporisateur_serial);
 start(temporisateur_simulator)
 test_debut_acquisition=true;
 set_param('simulator_model','simulationcommand','start');
 set_param('simulator_model/VR_Acquisition_Simulateur','value','1');
 catch msgbox('Unable to switch mode');
       test_debut_acquisition=false;
       stop(temporisateur_simulator);
 end
 end
end
%%%
function start_simulator_model(hObject, varargin)

selection = questdlg('Connect to simulator ?',...
      'Simulator',...
      'Yes','No','No'); 
   switch selection, 
    case 'Yes',
        try
          status = get_param('simulator_model','simulationstatus');
          if strcmp(status,'stopped')
          set_param('simulator_model','simulationcommand','start');
          set_param('simulator_model/VR_Acquisition_Simulateur','value','0');
          end