I was thinking of buying another Arduino, and the Leonardo looks appropriate.

However I am confused! The Comparative Tables seems to show 2 different Leonardos. (This table is very difficult to read with tiny black text on a grey background, and no key to the column headings.)

There appear to be different models "R3" and "R4" from different retailers and Element14 seems to have a "U4". Can anyone clarify the differences?

I assume I can use the Uno Prototyping shield on the Leonardo.

  • Wow! I'll have to talk to them about that. :) I think you can take that as a typo.
    – Nick Gammon
    Commented Jan 4, 2017 at 6:48
  • I think the pin-outs are the same on both boards (the pin spacings) so the shield should work on the Leonardo. The signals will differ a bit from the Uno to the Leonardo.
    – Nick Gammon
    Commented Jan 4, 2017 at 6:55
  • Personally I wouldn't buy the Leonardo unless I specifically needed the USB interface stuff (eg. mouse/keyboard emulation). There are more sketches for the Uno than for the Leonardo. However if you want to make something that simulates a keyboard, then the Leonardo is the way to go!
    – Nick Gammon
    Commented Jan 4, 2017 at 6:56
  • Personally I wouldn't buy either. I'd buy the chipKIT Lenny, but then I made it :P Not such good USB support yet though, so it depends what you want from it...
    – Majenko
    Commented Jan 4, 2017 at 10:31

1 Answer 1


At the end of the day the Leonardo is just a chip (ATMega32U4) on a board with a voltage regulator, a couple of LEDs and USB socket / shield headers. There's not much else to it.

Different revisions may change some of the support components - maybe a component went EOL and they needed to change it, or a better / cheaper one came along that they switched to - but the basic design of it - a chip on a board with minor support components - can't really change.

The reason it's hard to find the differences between the different revisions is because those differences are so inconsequential to the end user that knowing them is irrelevant. The only real way you'd find the differences would be to compare the schematics of each revision to find the components that have changed. In some cases it may even just be a change to the silk screening in re-branding from Arduino to Genuino, or just a slightly more modern logo, etc.

It's still the same chip, and still connected up in the same way.

  • In fact I decided to buy a Pro Mini instead, as I don't need USB.
    – Milliways
    Commented Mar 5, 2017 at 21:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.