avrdude: ser_open(): can't open device "\\.\COM3": Access is denied.

Hello Everyone, I'm about 2 months into learning Arduino. Everything has been going fine on the project book so I decided to work on my own project and this is when the subject line error popped up. It only occurs when I try the Arduino code along with hairless midi serial app and the loop midi app. I've read other posts that discuss going to device manager and changing the port but still no luck. I'm using the UNO board. To fix I uninstall and reinstall the Arduino program but same thing happens. It works for a couple runs then get this port error. If anyone has any suggestions that would be great. Thank you, Matt

Figured as soon as I post I played around and it works. Weird because I just went back and did same things I did before.

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Reinstalling the Arduino IDE or changing things in device manager are not going to help.

Only one application can have access to the serial port at the same time. If you open the port in Hairless, the Arduino IDE cannot access the serial port at the same time to upload a new sketch.

You have to close (or at least disconnect) Hairless before uploading.


Thank you for the help. I will be sure to read the posting rules next time.