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Topic: serial port already in use - out of the blue (Read 1 time) previous topic - next topic


I've been working with my arduino for a few weeks, and all of a sudden I'm getting "Serial port 'dev/cu.usbserial-A700063cV' already in use. Try quitting any programs that may be using it."

Obviously, I've quit every program and done everything I can think of to make sure nothing else could be using the same port, but nothing works. I've tested the arduino on another mac and it works fine, and I've created a new user account on my mac, and I get the same issue.

Thoughts? Any way to check in the terminal to see what could be blocking it?

Thanks in advance....


I know this is a PC type solution and you have a Mac but try un-installing the USB / serial driver and then re installing it and re booting.


Each serial device has two device special files - /dev/tty.whatever and /dev/cu.whatever.  This is two different ways for accessing the same port.  Make sure you aren't accidentally accessing the /dev/tty.* version from elsewhere.

Sometimes the network subsystem tries to grab serial ports, under the (old) assumption it is a modem.  That shouldn't happen without actually entering the network systems settings utility.

Are there lock files anywhere?  I don't recall...

I'm sure by this point you have tried the obligatory reboot to make sure any program that was using the port but went off into the bushes has been well and truly terminated.



Same problem for me here :(

busy usb port, I searched through the whole forum, installed and uninstalled the FTDI driver. But with no luck.

It did work until this morning: since then arduino program keeps giving the same error message:Serial port 'dev/cu.usbserial-A4001aGv' already in use. Try quitting any programs that may be using it."

So i am not able to communicate with the Arduino anymore. What am i doing wrong? Some help would be great.

I have an intel mac. v. 10.5.4
Arduino NG ATMEGA8
FTDI driver version 2.2.9 (i also tried it with 2.2.10)
Arduino 12


By reinstalling the system OS I managed to clear the usb/serial busy - thing. But there needs to be another solution for this... does it?


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