There are a number of different Arduino boards, which you can see by visiting the “Products” section of the Arduino website.
How is the Arduino Leonardo different from all other Arduinos?
The heart of the Arduino ino Uno is a microcontroller called the ATmega328. There is also a second microcontroller on the Uno, an ATmega16U2, which is responsible for handling the USB interface. You may have noticed this next to the USB connector.
The reason the Arduino Uno needs this second microcontroller is that the ATmega328 can’t process USB connections, while the ATmega16U2 doesn’t have enough of the features to make a seful Arduino.
The Arduino Leonardo uses the ATmega32U4 to handle the USB work as well as all the Arduino work you’re used to. This means
that the code necessary to do the USB work is, in a way, part of your sketch, and this means that you can manipulate the USB
behaviour from your sketch, using the special Mouse and Key board libraries. These libraries allow an Arduino Leonardo to appear as a mouse and/or keyboard to a connected computer.It turns out this allows you to do some pretty cool things.
There are now other Arduino boards using the ATmega32U4, such as the Arduino Yun, the Arduino Micro, and the Arduino Esplora, as well as the Arduino robot.
Other Differences Between the Arduino Leonardo and the Arduino Uno
there are a few other dierences between the Arduino Uno and the Arduino Leonard.
The main differences that you should be aware of are these:
- You may have learned how to use analogWrite() to control the brightness of an LED. It turns out that not every Arduino pin can be used for this. On the Uno, analogWrite() only works with pins 3, 5, 6, 9, 10, and 11, while the Arduino Leonardo can also analogWrite() on pin 13. This means you can control the brightness of the built-in LED that is connected to pin 13!
- When you connect an Arduino Uno to your computer, the USB serial connection is set up and stays there as long as the Arduino is connected to your computer, even if you reset your Arduino. Because the Arduino Leonardo creates the USB port in the sketch, resetting the Arduino Leonardo causes the USB serial connection to be broken and reestablished. Depending on what you’re doing, this may have implications. If you’re on Windows, it will probably make your computer beep a couple of times.
- The Arduino Uno has only 6 analogue inputs, A0–A5, which are all grouped together. The Leonardo has 12 analogue inputs, labeled A0 through A11. Inputs A0–A5 appear in the same locations as on the Uno, while inputs A6–A11 are on digital pins 4, 6, 8, 9, 10, and 12, respectively. These additional analogue input pins are labeled on the reverse side of the Leonardo.
- The Arduino Leonardo uses a Micro-B USB cable.
- The first time you plug a Leonardo into a Mac, the Keyboard Setup Assistant will launch. There’s nothing to configure with the Leonardo, so close this dialogue by clicking the red button in the top left of the window.
