Avrdude: ser_open(): can't open device "\\.\COM9": Access is denied

Software IDE 2.x
1

I do get the message "Access is denied" when trying to upload sketch if "Serial Monitor" is on.

2

For boards with FTDI serial-to-usb converter or when using a Pro Mini with an FTDI based erial-to-usb adapater it's a known issue; see "Access is denied" error when uploading to board w/ FT232 USB chip with Serial Monitor/Plotter open · Issue #1783 · arduino/arduino-ide · GitHub.

If you're using another board, please provide the details.

3

I experienced the "Access is denied" with a Nano clone w/old bootloader on Arduino IDE 2.1.1 and Win 11 PC.
Turning of "Serial Monitor" cured the problem.

Same thing does happen on a Pro Mini with an FTDI based serial-to-usb adapter.

2 Likes
4

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.