MATLAB: Are the serial ports unable to open with MATLAB

serial port

Hello, I am trying to connect a device through a serial port using the below code
%Set the below parameters
port = 'COM3';
Baud_Rate = 9600;
Data_Bits = 8;
Stop_Bits = 1;
%Default for Parity & Flow Control are none.  
S = serial('COM3','BaudRate',Baud_Rate,'DataBits',Data_Bits,'StopBits',Stop_Bits);
fopen(S)
fscanf(S)
The problem is: 1. I keep getting the following error
Error using serial/fopen (line 72)
Open failed: Port: COM3 is not available. No ports are
available.
Use INSTRFIND to determine if other instrument objects are
connected to the requested device.
 instrfind
   Instrument Object Array
   Index:    Type:     Status:   Name:  
   1         serial    closed    Serial-COM4
   2         serial    closed    Serial-PORT
   3         serial    closed    Serial-COM4
   4         serial    closed    Serial-COM4
   5         serial    closed    Serial-COM4
   6         serial    closed    Serial-COM4
   7         serial    closed    Serial-COM4
   8         serial    closed    Serial-COM4
   9         serial    open      Serial-COM4
   10        serial    closed    Serial-COM4
   11        serial    open      Serial-COM6
   12        serial    closed    Serial-COM6
   13        serial    closed    Serial-COM6
   14        serial    open      Serial-COM3
   15        serial    closed    Serial-COM3
   16        serial    closed    Serial-COM3
   17        serial    closed    Serial-COM3
   18        serial    closed    Serial-COM3
   19        serial    closed    Serial-COM3
   20        serial    closed    Serial-COM3
   21        serial    closed    Serial-COM3
   22        serial    closed    Serial-COM3
   23        serial    closed    Serial-COM3
   24        serial    closed    Serial-COM3
   25        serial    closed    Serial-COM3
2. The same serial port connects when I use alternative software such as MakerPlot or PuTTy.
At this point I have gone through a lot of the forums and have tried instrfindall, clearing MATLAB and running it again, I have double checked that I have the right port, and have also made sure that the alternative software does not have the port open, making it unavailable for MATLAB. No matter what I do or which port I use, I can't seem to get any port to open with MATLAB.
Any help you might be able to provide me would be greatly appreciated.
Thanks!

Best Answer

Your entry
14 serial open Serial-COM3
indicates that the port is already open.
You should use instrfind() to detect the possible open port and to delete the object if found.
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