I have got an Arduino Uno R3 on which I have an accelerometer that I'm playing a bit with. This setup has worked for quite a while now, everything working from uploading to checking the serial output.
Today I started having problems with the com port reporting busy or not connected at all. When I use the default IDE it cant find the arduino at all but when I use a modded IDE (Arduino ERW 1.0.5) seems to find the port to communicate on but it reports it being busy.
I have reinstalled the driver like 5 or 6 times now and searched for any other driver that might work but they wont change anything. I have also checked that my pc actually detects the arduino which it does, it is listed among the COM ports on Device Manager. I also tried changing the Com port from COM3 to COM4 and still it worked for like 3 uploads and then the COM port kinda "disappeared" from the serial port list on the IDE.
EDIT: Weirdly, after closing some programs that seem to have to do with serial communication it works. I have to look into what I close and when.
EDIT2: For now it seems that processing sometimes didnt close properly when not using the stop button on the processing application which then didnt close the connection to the arduino. I havent had any problems since I started to use the Stop button on processing.
Win 8.1
Latest driver and IDE(an modded IDE called Arduino ERW 1.0.5 seem to work a bit better but have the same issues)
One thing I noticed is that if I press the reset button when it starts again it wont send anything through serial, is it defaulting to the Blink program after a reset or what?
Best Answer
For those getting the "port busy" error while connecting Arduino and Process, one fix is to close the serial monitor in Arduino.