Error using fclose Invalid file identifier. Use fopen to generate a valid file identifier.

Hello,

My code is:

% Find a serial port object.
obj1 = instrfind('Type', 'serial', 'Port', 'COM3', 'Tag', '');

obj1.Baudrate=115200;
obj1.Timeout=2000;
obj1.Terminator='CR';

% Create the serial port object if it does not exist
% otherwise use the object that was found.
if isempty(obj1)
    obj1 = serial('COM3');
else
     fclose(obj1);
     obj1 = obj1(1)
end

% Connect to instrument object, obj1.
fopen(obj1);

%send message

fprintf(obj1,'#1Zmt\r');

%read the command

fscanf(obj1)

Could you please help me? If I use the tmtool first,connect to the instrument and then Run this code, it will work. But if I open Matlab and try to run it, it gives me this error.

Thank you

[Walter Roberson]

Your code does not check that the fopen works, but you should be checking that it works before trying to use the port

I do not know why it is failing