Instructables
Picture of Step by Step Guide to the Arduino Leonardo
The Arduino team is now shipping their latest creation - the Leonardo. It is the first Arduino to use Atmel’s ATmegaXU4 series chip with built-in USB. This change is big and it has big benefits. In addition to the built-in USB, it offers more digital and analog pins. This step by step  guide gives you the details you need to know to start using it.

For a more comprehensive guide, see my article - Arduino Leonardo versus Uno – What’s New.
 
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Step 1: More Digital Pins

There are four more digital pins. The Uno has 14 digital pins: D0-D13. The Leonardo has 18: D0-D17. The extra pins have been mapped to the ICSP header. Their mappings are:
  • D14 – MISO – PB3
  • D15 – SCK – PB1
  • D16 – MOSI – PB2
  • D17 – SS – PB0
Pin D17 (SS) does not have a corresponding pin on the ICSP header, nor anywhere on the board. In order to use it, you must solder a wire to either the end of the Rx LED or the via attached to it - see photo.

Step 2: Extra PWM pin

The Leonardo has 7 PWM pins instead of 6. ATmega32U4 also has a new timer, timer4 which has 10 bits and uses a PLL to count at 64MHz. Their mappings are different as well:
  • D3:  8-bit timer0
  • D5:  16-bit timer1&3
  • D6:  10-bit timer4
  • D9:  16-bit timer1&3
  • D10:  16-bit timer1&3
  • D11:  8-bit timer0
  • D13:  10-bit timer4
brianfit5 months ago

Nice intro. One addition: in addition to Linux being Leonardo-ready, you don't need to install USB drivers for OSX either. :-)

creasty1 year ago
hey,friend it's look like u have a great knowlage on arduino i need ur help,i m new to arduino..i want to run arduino programme which i'hv (made for leonardo board only) and check whether there is any error in programme or not..and than i want to upload this programme in programme board and acorrding to programme it'll run 2 gear motor,so how can i check it and load it..can u please tell me step wise instruction or put this instructable type vedio..i'll be thankfull,thank you
fandujar711 year ago
The shield is a Motor Shield like a Adafruit v1.2, compatible with Uno but not with Leonardo.
fandujar711 year ago
Have you got any diagram of how to mapping the pins between a shield for Uno that is not compatible with Leonardo directly?
Can it be done using a breadboard?

Thank you.
jibblesmgee2 years ago
But... you can't remove the microcontroller? I thought the whole point of Arduino was to program a microcontroller, remove it, and then put it in another project... They expect people to buy/make a new board for every project?

I won't be buying one, not unless they start putting a socket on it instead of surface mount soldering it to the board.
bhubbard452 years ago
All I ever really wanted was an extra 5V pin
IF only I'd know a little earlier I wouldn't have bought an Uno, Thanks for sharing.
i know, i bought an uno the day before Maker Faire Bay Area and then it was released there and was introduced by Massimo Banzi himself in his presentation and i felt kinda sad because it was cheaper and better. Luckily i was able to get one before all of the first 100 leonardo's were bought for $20 in the MakerShed there. But then when i got home i examined it and had no idea about the extras, so this instructable has helped me.