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

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Od Di
Od Di 2017-4-8
评论： Madalina Dobre 2021-12-12
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.

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回答（5 个）

Nim Pim
Nim Pim 2021-5-2
编辑：Walter Roberson 2021-6-5
Disconnect and delete all the objects using "instrreset". Then it works.
https://in.mathworks.com/help/instrument/instrreset.html
Saurabh Gupta
Saurabh Gupta 2017-4-12
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
  2 个评论
Peter Nelson
Peter Nelson 2019-3-26
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
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 2019-6-4
Does work for me so far with an elegoo MEGA2560 R3.
Thanks for your help.
alican kara
alican kara 2020-6-20
编辑：Image Analyst 2020-6-20
MATLAB Serialport connection between Computers
https://www.youtube.com/watch?v=YIhblJn1hPA&t=1s

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