The Arduino ATmega328 NANO uses COM3 on my WINDOWS 10 computer, but COM3 is NOT available.

QUESTION: Please explain in detail how I can change this Arduino NANO to operate on COM4

  • 2
    What do you mean com3 is not available...?
    – Majenko
    Apr 10 at 12:15
  • 1
    if COM3 is not available, then the Nano is not using COM3 or it is not plugged in or it has failed in some way
    – jsotola
    Apr 11 at 5:09

In device manager, right click on the device and select "Properties". Then go to the tab "Connection properties" and click on "Advanced". There you can change the COM port number assignment for a particular device.


In general, Windows assigns COM ports to USB devices when they are plugged in the first time. If you have multiple USB sockets, the same physical device will be assigned a different COM port when plugged into different sockets. Is it possible that you have changed your setup and are now using a different USB socket? Try the others to see if that works.

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