Introduction: 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.
Step 1: More Digital Pins
- D14 – MISO – PB3
- D15 – SCK – PB1
- D16 – MOSI – PB2
- D17 – SS – PB0
Step 2: Extra PWM Pin
- 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
Step 3: More Analog Pins
The correspondence of each analog with their digital counterparts is as follows:
- A0 – D18
- A1 – D19
- A2 – D20
- A3 – D21
- A4 – D22
- A5 – D23
- A6 – D4
- A7 – D6
- A8 – D8
- A9 – D9
- A10 – D10
- A11 – D12
Step 4: SDA/SCL Pins Are Different
The pins supporting I2C/TWI previously used analog pins A4 & A5. Now these pins are located at digital pins D2 & D3. While the SDA and SCL pins are in the same location on the board, because of the underlying hardware mapping changes, it may affect the operation of certain shields and any software using these two pins.
Step 5: Serial Port Differences
There is now a second serial port. The primary port is built into the USB interface and the Tx/Rx LEDs are attached to it. The secondary port is located at pins D0 & D1. This port does not have any LEDs attached.
To use the primary serial port, use the class Serial as usual. For the secondary port, a new serial class called Serial1 has been created. You use it the same way as the Serial class.
Step 6: Keyboard and Mouse Emulation
Of course the most exciting new feature is direct USB support. That means it can operate as an actual USB device. It can emulate a computer mouse, keyboard, or both.
The Arduino library has made it really easy to do by creating a two new classes - one for emulating a mouse, and the other a keyboard.
Step 7: Last Steps
First, you must upgrade your Arudino IDE to version 1.01. It adds the support needed for this new board, plus it has a lot of nice new features.
Second, unless you are using Linux, you will need to install USB drivers for the Leonardo.
This step-by-step guide is a just a brief overview. For more detailed information, please see the article: