I'm trying to open a serial port, but Matlab says it's not available. What can i do?

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Hi everyone, I know a lot of people already asked for this but i cannot find any solution. I've got an Arduino board connected to a serial port (COM5), but when i run fopen(serialobj) it fails saying that "COM5 is not available". I tried to open Arduino IDE and uploading another sketch on that port and it went well; even though I close the IDE matlab still gets the same error. I tried with INSTRFIND and the output was
Index: Type: Status: Name:
1 serial closed Serial-COM2
2 serial closed Serial-COM2
3 serial open Serial-COM5
4 serial closed Serial-COM5
5 serial closed Serial-COM3
6 serial closed Serial-COM5
7 serial closed Serial-COM3
8 serial closed Serial-COM3
9 serial closed Serial-COM3
The error message given by Matlab is this:
'Open failed: Port: COM5 is not available. No ports are available.↵Use INSTRFIND to determine if other instrument objects are connected to the requested device.'
Can someone help me? PS: Baudrate is 4800, the same as the one i set on Arduino.

Answers (5)

Nim Pim
Nim Pim on 2 May 2021
Edited: Walter Roberson on 5 Jun 2021
Disconnect and delete all the objects using "instrreset". Then it works.

Saurabh Gupta
Saurabh Gupta on 12 Apr 2017
It looks like you already have the port open. You may want to fclose or delete it before trying to fopen it.
  2 Comments
Peter Nelson
Peter Nelson on 26 Mar 2019
Doesn't work for me. I tried inserting the solution provided in the answer from SG:
if ~isempty(instrfind)
fclose(instrfind);
delete(instrfind);
end
but I still get the error. The only fix is to leave and re-start Matlab.... sometimes several times before it allows me to open it with the serial command. In my case its a USB port. Any other ideas???

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Davide Nicolò Fortunato
Davide Nicolò Fortunato on 19 Apr 2019
I have the same problem, but i have an elegoo uno board. (the microcontroller is the same atmega of arduino uno).
i have yet tried
if ~isempty(instrfind)
fclose(instrfind);
delete(instrfind);
end
but nothing :(

Renner Josef
Renner Josef on 4 Jun 2019
Does work for me so far with an elegoo MEGA2560 R3.
Thanks for your help.

alican kara
alican kara on 20 Jun 2020
Edited: Image Analyst on 20 Jun 2020
MATLAB Serialport connection between Computers

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