Problem with fwrite command matlab in serial communication

Thanks for answering !

I have a problem with fwrite command matlab in serial communication.

First, these shows you my code

in file testx.m ---------------- s=serial('COM4');

set(s,'BytesAvailableFcn',@BytesAvailable_Callback);

set(s,'BaudRate',38400);

set(s,'BytesAvailableFcnMode','terminator');

set(s,'Terminator','LF');

set(s,'ReadAsyncMode','continuous');

flushinput(s);

global x

global k

k=0;

x=cell(0);

fopen(s);

-------------

this in in BytesAvailable_Callback.m

-----------------------

function BytesAvailable_Callback(obj,event)

if (get(obj,'BytesAvailable')~=5)

    disp('Error data');

else

    disp('Data is 5 bytes (4 bytes a float and a byte LF)');

    d=fread(obj,1,'float');

    % fread(obj,1,'char');

    global x

    num=numel(x);

    x{num+1,1}=d;

end

flushinput(obj);

-----------------

I am trying communicating with my Atmega16 chip. When starting, my chip sends through USART 4 bytes of a float and finishes with a LF byte (10 in char).

When I program, this float is 3.454. Matlab received this number (3.454). But when running, I command these:

flushoutput(s);

fwrite(s,10000000.647767567567,'float','async');

Matlab was not call the BytesAvailable_Callback although when I uses the fread command in workspace, I saw there had many LF bytes. (I programmed my chip send the float number had received through USART).

Thanks for help.