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

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.

[Enrique Paredes Sánchez]

I had the same problem, it was due to another program was using the port. I closed it and then it solved.

Answer 1

[Nim Pim]

Disconnect and delete all the objects using "instrreset". Then it works.

https://in.mathworks.com/help/instrument/instrreset.html

[Faheem Ershad]

This worked for me!

Answer 2

[Saurabh Gupta]

It looks like you already have the port open. You may want to fclose or delete it before trying to fopen it.

https://www.mathworks.com/matlabcentral/answers/322930-why-are-my-serial-ports-unable-to-open-with-matlab

[Peter Nelson]

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???

[Madalina Dobre]

hi,did you get a fix for this? i have the same issue

Answer 3

[Davide Nicolò Fortunato]

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 :(

Answer 4

[Renner Josef]

Does work for me so far with an elegoo MEGA2560 R3.

Thanks for your help.

Answer 5

[alican kara]

MATLAB Serialport connection between Computers

https://www.youtube.com/watch?v=YIhblJn1hPA&t=1s