The Eclipse Serial Monitor on Mac OSX
Out of the box when using the serial monitor in Eclipse will likely produce an error message similar to this:
Serial port ‘/dev/tty.usbserial-A4001KX4’ already in use. Try quiting any programs that may be using it
This thread on the Arduino Forum explains the reason for it and this thread on Stackoverflow provides a little more background.
In essence what needs to be done is the following:
- Open the terminal application
- At the user prompt execute these two lines:
sudo mkdir /var/lock
sudo chmod 777 /var/lock
This will create a directory /var/lock and then changes the default access to it.
Now the Serial Monitor in Eclipse will work as explained in Jantje’s video
Trippy Lighting 
I appreciate this thread but in my setup I still have to disconnect the serial monitor before I can upload a new image. Any ideas?
I am sure you’ll agree that this is a hard to answer question without knowing what your set-up is 😉
This thread really does not address having to disconnect the serial monitor before uploading a hex file.
I personally use Teensy boards and have found this still to be necessary but not per-se a problem.
Indeed I was a little light on the info. Obviously I’m using Mac OS (albeit still snow leopard on that particular machine). I had thought that with Eclpse Arduino you didn’t have to disconnect the monitor but it’s interesting you have to w the teensy. Do you happen to know which serial driver it uses (the one I in the arduino ide or the one in the Java extensions)?
The 2.2 stable versions of the Arduino Eclipse IDE I believe still use the RXTX serial driver the Arduino IDE used. The newer 2.4 (nightly builds) version now use JSSC. I am not sure if the Arduino IDE use the same by now.
Also, please be aware the the very newest Arduino 1.6.6 does not yet work with the Arduino Eclipse IDE. 1.6.5 is fine.
I am in process of updating all that myself.
Thanks. I’m using the nightly build and 1.6.5.