user220: I know there are different revisions of the Arduino Uno itself, but are there any revisions of the SMD? If they are is SMD R2 identical to through-hole R2? I have a board marked R2 SMD and I am wondering if that is the only version that they produced in SMD format and just are signifying that it is compatible with the standard R2.

user8: The only difference with the SMD Uno is the fact you can't remove the chip. There are also 2 extra analog comparators not connected to anything.
The SMD boards are compatible with the thru-hole boards, but they have SMD components, which apparently make them easier to make and cheaper. As I said before, the two extra analog inputs (A7 and A6) are left unconnected on the official boards.
Here is my Uno R3:


220: <p>I know there are different revisions of the Arduino Uno itself, but are there any revisions of the SMD? If they are is SMD R2 identical to through-hole R2? I have a board marked R2 SMD and I am wondering if that is the only version that they produced in SMD format and just are signifying that it is compatible with the standard R2.</p>
 8: <p>The only difference with the SMD Uno is the fact you can't remove the chip. There are also 2 extra analog comparators not connected to anything.</p>

<p>The SMD boards are compatible with the thru-hole boards, but they have SMD components, which apparently make them easier to make and cheaper. As I said before, the two extra analog inputs (A7 and A6) are left unconnected on the official boards.</p>

<p>Here is my Uno R3:</p>

<p><img src="https://i.stack.imgur.com/5miJQ.jpg" alt="enter image description here"></p>
