serial port com 3 not found

I have been learning my new UNO board today and was very happy with the results untill I got to the servo tutoral.

the program ran fine but now I cannot upload a new program. I get a message that the com port cannot be found.

I saw a couple of references to this on the forums but I am no software wizard. I can get through some simple code but the fix they are talking about is greek to me.

I need help. :fearful:

Look in the installation + troubleshooting forum and try com 8 for an uno not com 3.


Open the Arduino IDE with the Arduino unplugged and look at the list of COM ports offered in Tools -> Ports. Plug in the Arduino and look at the list in Tools -> Ports again. There should be a new entry. Select that one. Now everything should work OK.

Replying to my own post.

I left Friday frustrated that I had no communications.

I take my laptop home on the weekends and this morning when I plugged everything back in I had good communication and was able to upload programs.

I do not know what the problem was But I feel like it was just a reboot situation. I am no computer Geek, so I do not have a clue why the comm went down or why it is working now.

This appears to be an issue from reading the other postings. I am planning to use this board in a consumer (medical) product, So it needs to be rock solid.

At the moment, I am functional. Further testing and development will hopefully weed out the communications problems. I hope it was a one time thing.

What kind of computer are you using? When you plug the UNO into a computer, it registers itself as a COM port. Usually the OS (Windows, specifically), picks the next available unused COM port. It is not unusual for the COM port to change the next reconnecting the UNO, especially if you have used other COM port devices or if the Device Manager is cleared of all previous instances of COM ports. Whenever you see this error message, just look at the "Port" menu as described above and select whichever port you see. If you see multiple COM ports listed, try each one until you find the one that works.