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Using "serial" to connect to an Arduino

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I got an Arduino for xmas, and I'm trying to talk to it from MATLAB (R2012a prerelease) via the serial interface. I'm not having any luck at the moment, I can talk to it from python no problem. Here's what I've got:
>> s = serial('/dev/ttyACM0', 'BaudRate', 9600);
>> fopen(s)
Error using serial/fopen (line 72)
Open failed: Port: /dev/ttyACM0 is not available. Available ports: /dev/ttyS0.
Use INSTRFIND to determine if other instrument objects are connected to the requested device.
But in ipython:
In [1]: import serial
In [2]: s = serial.Serial('/dev/ttyACM0', 9600)
In [3]: s.readline()
Out[3]: '408\r\n'
I've tried '/dev/ttyS0' and made sure I closed old connections, but I still get this error. I've run out of ideas, anyone have suggestions?
  1 Comment
Thomas Ibbotson
Thomas Ibbotson on 4 Jan 2012
Forgot to point out that I'm on 64-bit linux (Ubuntu 11.10)

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Accepted Answer

Thomas Ibbotson
Thomas Ibbotson on 5 Jan 2012
I found the following solution on the newsgroup:
Hi Patrick
You can use /dev/ttyACM0 but you need to let the library know that you will be using it. To specify the ports on your system, create a java.opts file in the directory you start MATLAB from with the following line in it:
After you restart MATLAB, the port should be found:
>> instrhwinfo('serial')
ans =
AvailableSerialPorts: {2x1 cell}
JarFileVersion: 'Version 2.7.0'
ObjectConstructorName: {2x1 cell}
SerialPorts: {2x1 cell}
>> ans.AvailableSerialPorts
ans =
Another option is to create a symbolic link from /dev/ttyS101 to
/dev/ttyACM0. The port should be enumerated as ttyS101 then.

More Answers (4)

Walter Roberson
Walter Roberson on 4 Jan 2012
Is ttyACM0 a virtual USB port? If so then the device needs to be connected when you start MATLAB, as MATLAB only scans the device table once.

Jan on 19 Apr 2012
i got the same problem. using ubuntu 11.10 and matlab 2010b with arduino ide 1.0
in which folder do i have to put the java.opts file?
/usr/local/MATLAB/R2010b/ ?
Thomas Ibbotson
Thomas Ibbotson on 19 Apr 2012
You could add the java.opts file to /usr/local/MATLAB/R2010b/matlab/bin/glnxa64/ if you have write permissions there.
Alternatively you can put it in the MATLAB startup directory i.e. the directory MATLAB returns from 'pwd' before any other code is run (which is the directory you were in when you called the command from if you launch MATLAB from the prompt, or if you've set up a desktop launcher for MATLAB, it is usually your home directory).
Thomas Ibbotson
Thomas Ibbotson on 19 Apr 2012
I assumed you're on 64-bit linux, if it's 32-bit then the directory will be glnx86. In any case you can find out from MATLAB which architecture you are using from the command:

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Jan on 19 Apr 2012
ok, thank you! it s working :)

Bagus Tris Atmaja
Bagus Tris Atmaja on 7 Feb 2015
I have same problem with Matlab 2013 in Ubuntu 14.04. When I try fnd info from serial port, it is live,
>> instrhwinfo('serial')
ans =
AvailableSerialPorts: {'/dev/ttyS101'}
JarFileVersion: 'Version 3.3'
ObjectConstructorName: {'serial('/dev/ttyS101');'}
SerialPorts: {'/dev/ttyS101'}
but, when I connect it with arduino (using ArduinoIO package),
>> a=arduino('/dev/ttyS101');
Attempting connection .............
Warning: Unsuccessful read: A timeout occurred before the Terminator was reached.
Error using arduino (line 104)
Connection unsuccessful, please make sure that the board is powered on, running a
sketch provided with the package, and connected to the indicated serial port. You
might also try to unplug and re-plug the USB cable before attempting a
Any idea? I guess the error from ArduioIO package


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