Permission denied on dev/usbX

We have a problem in our student labs that we've been unable to solve. We're running Windows XP

We've installed the USB to serial drivers, and have verified in Device Manager that the port we've selected in Arduino matches the USB to Serial port.

The problem occurs when attempting to upload a sketch. Java throws an exception (I can't post it all now but might get a chance later today) but the last line we see is

permission denied dev/usbX

where X can vary, and is always the correct port. (Another line in the exception is 'portInUse')

Our sysad assures me that O/S access permissions are the same for all students, and that they have permission to install and uninstall drivers. I've tried:

  • Uninstalling the drivers and then reinstalling the drivers.
  • Having the Arduino plugged in when logging in and not having it plugged in.
  • Running the Arduino software from the batch file and not.
  • Trying other USB ports (noting that X will change, as expected)

and none of these work. We're at our wits' end here!

Any help would be appreciated.

I'm guessing the error says "/dev/com7" (not usb7). (It doesn't really matter, but I was initially confused by the usb7).

The problem is most likely that the port really is in use (only one program can use the serial port at a time). Are these computers running any firewalls (some block access to serial ports)? Or any PDA sync applications (which sometimes grab serial ports because they might be PDAs)? Do you have Max/MSP or Processing or another program running with which you are attempting to talk to the Arduino boards?

Also, see: for other possibilities I may have forgotten.

Thanks- this could be the issue- there are such proggies running on these machines. The weird thing is that it does work on some. Anyway, that's something to investigate.

Yea, give that a shot… usually if you’ve got the driver installed correctly (which it sounds like you do), the problem is that some other program is being greedy with the serial ports.