How do I change COM port when greyed out?

I have just installed the software on my computer and it says in the bottom right "Arduino Uno on COM1" when I click on tools the 'Serial port' option is is greyed out so I can't change it even if it had any options.

How do I change the port?


did you install the driver provided in the software?
what os do you use?

Yes, I did install the software. I have also uninsulated it and re-installed it afresh. I am using windows 7.


OK, I rebooted the computer and now I can get to the Port it shows COM3 with a tick.

now when I try and upload a sketch I get the following error message:

avrdude: stk500_getsync(): not in sync: resp=0x00

So now what do I do? - What is “not in sync”?


It means the software isn't able to communicate with the bootloader on the 328. It's, by far, the most common and generic error.

First disconnect the board to make sure your new board is com3.

Where did you get the Arduino? Have you tried another cable? Which board is it? Have you run the loop back test (top of this forum).

Hi James,

The board is not new. the computer is. I have checked and it is all working on COM3.

I bought the Arduino over a year ago and it has been fine up until now. It is a genuine UNO R3 (not a copy)

I have not run the loop back test - I don't know what that is - I will investigate it...