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Topic: Serial port 'COM19' already in use (Read 9 times) previous topic - next topic


Hi all,

Would appreciate if anyone can share how to solve the problem of com port in use when trying to upload sketches.  I realized that I can only upload new sketches to the board by rebooting with the serial port disabled and enabling it after the system restarted.  All this is done with the board plugged in (to force the assignment of port to the board? doesn't seem right either...). It didn't work when I reboot without disabling the serial port.

Strange strange strange.

Anyone has any solution or has encountered this problem?



Your workaround continues to point to other software on your computer that is blocking the serial port.  It could be anti-virus, blue-tooth, or a range of other programs that are causing the conflict.


Anyway to find out which program or device is also using the same com port?  Can't find the information in Device Manager.

The strange thing is, regardless of what com port I changed to, the same problem occurred, giving me the impression that Arduino is preventing itself from using the com port (different threads of same program using the com port and blocking the other?).

I tried disabling norton AV, bluetooth, and other programs visible to me without avail.

Any suggestion to test?


Feb 07, 2009, 03:35 am Last Edit: Feb 07, 2009, 03:37 am by madworm Reason: 1
How about using a different OS ?
Windoze for gaming, something useful for the rest.

Can't comment on Vista. It's on my laptop, but only for purpose of reselling it sometime. Never used it, too many colors, ugly explorer.

I know this doesn't help much, but I've long given up thinking about the other OS, expect for running games. XP had become a decent flavour of windoze with SP2, Vista doesn't really exist, the W7 may be better, maybe not.
• Upload doesn't work? Do a loop-back test.
• There's absolutely NO excuse for not having an ISP!
• Your AVR needs a brain surgery? Use the online FUSE calculator.
My projects: RGB LED matrix, RGB LED ring, various ATtiny gadgets...
• Microsoft is not the answer. It is the question, and the answer is NO!


I've posted it in another thread but realized that the problem I encountered is different from the thread starter.  Pardon me transferring it here.  Hope someone can help.

I realised one thing while trying to figure out the port already in use problem.  After getting it to work following the cumbersome way of disabling, rebooting and enabling the serial port, I realised that it may be the ide refusing to release it hold on the port (pardon me if I am technically incorrect with terms and jargons here).

When I quite the IDE and started it again, the uploading works ok.  Once I plugged out the USB cable and plug it back again, the problem starts.  This occurs regardless of whether I unplug the usb cable with IDE running or after I shutdown the IDE.

So it seems to me that the device still hanging on to the serial port is the IDE than any other program.

Anyone has any solution or things I can try with?

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