Error in sending data from arduino to matlab - matlab

Question

I want to run simple example in arduino and send data from arduino to matlab for drawing plot,
my arduino code is following:
#include <SoftwareSerial.h>
int i=0;
void setup()
{
Serial.begin(9600);
}
void loop()
{
Serial.println(i);
i++;
}
and my matlab code is following:
arduino=serial('COM4','BaudRate',9600);
fopen(arduino)
x=linspace(1,100);
for i=1:length(x)
y(i)=instrfind(arduino);
y(i)=fscanf(arduino,'%d');
end
fclose(arduino);
disp('making plot..')
plot(x,y);
But I've faced with error! The following is matlab error:
Error using serial/fopen (line 72)
Open failed: Port: COM4 is not available. No ports
are available.
Use INSTRFIND to determine if other instrument
objects are connected to the requested device.
Error in kh (line 2)
fopen(Arduino)
and here is arduino error:
avrdude: ser_open(): can't open device "\\.\COM4": Access is denied.
My arduino uno (COM4) driver in device manager are installed.
I use matlab 2013a and َArduino 1.8.1 Genuino
How can I fix this error?

Answer 1

If you are using RS-232 for Arduino IDE/Monitor to communicate with your Arduino on COM4.
Since RS-232 is a point to point methodology, you can only have one program/device on each end unless you add a bunch of hijinks.
When you have the Arduino IDE/Monitor open it uses the com port and other programs are denied access.
I think you need to close the Arduino monitor program to release Com port 4 and then the Matlab program should be able to open the port.
PS : Test this using a terminal. Obviously the port needs to be open for the terminal to receive the arduino's prints. The terminal DOES open when you have the arduino ide open, but it DOES NOT open when the arduino's COM terminal is open. So theoretically, MATLAB shouldn't be having a problem when just the IDE is open.

Answer 2

This is how I solved the problem.
In device manager you will find the Arduino COM port.
Go to the Advance properties of the port
Set the COM port number to COM4
Then replug the USB.