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.

Arduino Leonardo

For a more comprehensive guide, see my article – Arduino Leonardo versus Uno – What’s New.

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


For more detail: Step by Step Guide to the Arduino Leonardo

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