New UNO Won't Talk

I've been using an UNO with a DIP processor for a few weeks - going very well. Acquired a new UNO, SMP edition, that blinks the "L" LED but will not talk with through COM 3 that works well with the other. When first plugged in, Win-XP recognized the new peripheral and I clicked on "install drivers" and Win-XP now doesn't flag when the SMP UNO gets plugged in.

I tried all the COM baud rates and have tried the procedures that work with the other UNO: IDE simply can't find COM3 when the SMP UNO is plugged into it, with its "L" LED blinking. Restarting the IDE & SMP UNO over and over that works with the other UNO hasn't worked for this one. Under the IDE Tools: Board there is only one Arduino UNO. Am I missing something?


Try Connecting both the Arduino's at same time ,then donot start your arduino IDE just look for the Windows prompt ,it should come afresh because the other one UNO(DIP) is connected and recognized as the specific driver is installed that catches up with the com3 port. then plug in the SMD now it should prompt for a new device connected then install it's .inf (and yes UNO's have no DRIVER's, they have .inf files which makes UNO better for newer WINDOW version's).

Thank you for your response Nishant.

I only have one USB cord and when I procure another, I'll try what you suggest.

Also try these instructions:

Thanks everyone! It's now working great!

I am impressed by the lot of people with problems like this.

I don't know what they are thinking but using an arduino WILL REQUIRE to read some documentation, the setup is part of this process. This forum needs a bigger warning above about "please read first this faq"

it's nice to know that it's now working.