I recently decided to buy an Arduino UNO R3, to test compatibility with my sketches, which I have been testing w/ a Deumilanove. The UNO R3 contains an ATmega16U2 instead of an FTDI chip to do the serial to USB conversion, as well as 3 extra pins on the digital side of the board: SCL/SDA/AREF. One thing I don’t like about the Arduino UNO is that while it uses a 16MHz crystal for the 16U2, the main 328P MCU runs on a resonator, which is not as accurate. I found the EKitsZone UNO Rev.3 on eBay for $14.99, and decided to give it a try.
- the ATmega328P uses a 16MHz crystal oscillator instead of a resonator, so its timing is just as accurate as a Deumilanove
- the reset button is mounted at a right angle, so it’s easily accessible even when a shield is attached on top
- it uses a mini-USB connector instead of a full-sized one
- the JP2 pins aren’t filled with solder, so it’s easier to solder in headers, should you want to connect something the PB4..PB7 pins on the 16U2
- the programming header for the 16U2 isn’t installed, but it’s easy to solder one in
I see 1-4 as advantages. Plus, the board is a cool looking red color.