Arduino Leonardo vs. Arduino Uno

For what its worth, my experiences of using the Leonardo.

Nice write-up! I was wondering a little myself, what the differences might be between the boards.

Indeed a nice write up.
I have bought some leonardo 's and in contrast to Si I had some bad experiences.
The first thing that completely baffled me was the double use of the USB. The USB port uses 2 com ports. one to upload and one to use for the serial monitor. Both ports are not active at the same time. Which means that when you plug in the board first the Upload com port is activated (pling) then it disappears (plong) then the serial monitor com port is activated (pling). On my system that means lost of sound (pling plong) :wink:
When I rest the leonardo it goes (plong;pling;plong;pling)
I was surprised not to read anything about this behavior in the article.
Maybe it is a windows thing? (I'm mostly using Windows)
Then I got problems with 64bit RXTX dll. ( I admit I'm not using the Arduino IDE)
That is when I switched back to the old boards. Maybe I should take a new look and stick to 32 bit tools.

Best regards

I was surprised not to read anything about this behavior in the article.

Ah, you see I am a Mac person.

However, there is the annoyance on the Mac, that every time you plug it in, it decides you have got a new keyboard and invites you to identify it by pressing certain keys. Fortunately it carries on anyway, so you can just ignore the window.

The OP link seems down or broken... And since this is the #1 result on google for the topic, I think it's OK to reply to it.

Speeli Has a great comparison list between UNO & Leonardo, You could check it out.

Speeli UNO vs Leanrdo Comparison List

Some observations/corrections/suggestions for the comparison lists:
Uno has 20 digital I/O pins, 6 of which are also analog input pins.
Leo has 23 digital I/O pins, 12 of which are also analog input pins.
Uno has 3 digital pins on the ICSP header which are repeats of pins on the digital header, pins 11, 12, and 13.
Leo has 3 digital pins on the ICSP header which are unique and not repeats of other pins, pins 14,15, and 16. This is why Leo has more digital pins.
Leo RX LED is digital pin 17
Leo TX LED will be digital pin 24 in the future when issue 3129 fix makes its way into an IDE release

It is not entirely accurate that pinMode(14, OUTPUT); “did not work.” It is just a different pin number mapping, so on the Leo pin 14 was working with one of the pins on the ICSP header.
Both Uno and Leo have I2C pins shared with some other pins. Leo shares them on digital pins 2 and 3, Uno on analog pins 4 and 5
Both Uno and Leo have only one hardware serial UART. On the Uno it is UART0 and on the Leo it is UART1. The serial port connected to the Leo USB uses CDC (communications device class) to simulate UART functionality.

Thanks for this piece and the contributions of others. I really had to read up on the differences between the two boards, but your post was really helpful. Vielen Dank!