Hi,
after some time of flawlessly work with Arduino UNO, i've switched to a new machine (Windows 10) and I can't get it to work (previously I was using Win 7).
Whenever I try to upload a sketch, I get the following error: avrdude: ser_open(): can't open device "\\.\COM3": Access denied.
This happens no matter what port number I set my Arduino to in the Device Manager (and of course in the Arduino IDE accordingly).
BUT if I kill the "java (tm) platform se binary (32-bit)" process in the Task Manager, Arduino will upload the sketch just fine.
Why is that? Thank you in advance for any answer.
Probably because you have some sort of java program running on your PC that's using the COM port.