Receive data from a microprocessor

I am making a user interface with app designer and I want to receive the data stored in a microprocessor. I have performed the following functions but no data is stored in the variables and I do not know where I could be the error. These are the functions:

function read(app) 

   app.DataReceived_ch=fread(app.t_waveforms);

% Two 8-bit values are read for each 16-bit integer

          i=1;
          j=1;
           while i<length(app.DataReceived_ch)
            app.B(j) = 2^8*app.DataReceived_ch(i+1)+app.DataReceived_ch(i);

% The int numbers greater than (2 ^ 16) -1 are converted to negative

          if app.B(j) > 32768
             app.B(j)=app.B(j)-65536;
          end
            i=i+2;
            j=j+1;  
           end

        app.H1=length(app.B)-4;
        app.B=0.1*app.B;
        app.B1(1 : app.H1/4)=app.B(1 : 0.25*app.H1);    
        app.z1=app.B1;
        app.z1
        app.B2(1 : app.H1/4)=app.B(1+(0.25*app.H1) : 0.5*app.H1);   

        app.z2=app.B2;

        app.B3(1 : app.H1/4)=app.B(1+(0.5*app.H1) : 0.75*app.H1);    

        app.z3=app.B3;

        app.B4(1 : app.H1/4)=appp.B(1+(0.75*app.H1) : app.H1);

        app.z4=app.B4;

flushinput(app.t_waveforms);

pause(0.2); 

         end  % function read

and the start function is:

function startupFcn(app)
            app.tip=app.IPField.Value;

              app.t_waveforms = tcpip(app.tip, 80);

              app.t_buttons = tcpip(app.tip, 80);

              app.t_waveforms.BytesAvailableFcn = @read;  

              app.t_waveforms.BytesAvailableFcnCount = app.buffer+8; % to specify that the event be set to "Number of bytes" instead of "Terminator"

              app.t_waveforms.BytesAvailableFcnMode = 'byte';

              set(app.t_waveforms, 'InputBufferSize',app.buffer+8);

             app.z1 %To see if data are stored in z1
  end