Avrdude: ser_open(): can't open device "\\.\com4": access is denied.

Question

Problem :

I am beginner to  Arduino Uno. I have very recently installed the new IDE on my Laptop and suddenly I started facing below error if I tried to compile the program. I am using the Arduino Uno for the very first time.

“Avrdude: ser_open(): can't open device "\\.\COM4": access denied”

I am trying very hard to fix above error from past couple of days but still unable to fix it.

Please help me in fixing above error.

Answer 1

I know the solution for your issue. I also encountered the same issue in recent past. I had the outside cameras attached to my Laptop. So I tried to switch off the external cameras Once my cameras were off my program worked. So it was a camera software that was using my port.

In your case I think you are trying to use the "Eclipse" and "Arduino" simultaneously. Because of this I think your "com4 Port" conflict is happening and as a result the upload was interrupted.

So to fix your issue you need to restart your laptop and after that try to open your "Arduino" first and then try to upload. And do not open your "Eclipse" at the same time.