Arduino Leonardo

The Arduino Leonardo is a microcontroller board based on the ATmega32u4. It has 20 digital input/output pins (of which 7 can be used as PWM outputs and 12 as analog inputs), a 16 MHz crystal oscillator, a micro USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with an AC-to-DC adapter or battery to get started. 

The Leonardo differs from all preceding boards in that the ATmega32u4 has built-in USB communication, eliminating the need for a secondary processor. This allows the Leonardo to appear to a connected computer as a mouse and keyboard, in addition to a virtual (CDC) serial / COM port. It also has other implications for the behavior of the board; these are detailed on the getting started page.

The ATmega32u4 has 32 KB (with 4 KB used for the bootloader). It also has 2.5 KB of SRAM and 1 KB of EEPROM

DataSheet – http://www.atmel.com/devices/atmega32u4.aspx

Eagle Files – https://www.arduino.cc/en/uploads/Main/arduino-leonardo-reference-design_3b.zip

Schematics – https://www.arduino.cc/en/uploads/Main/arduino-leonardo-schematic_3b.pdf

Tech Specs:

• Microcontroller:  ATmega32u4
• Input Voltage (recommended): 7-12V
• Maximum Voltage range: 6-20V
• Operating Voltage: 5V
• Digital I/O Pins: 20
• PWM Channels: 7
• Analog Input Pins: 12
• DC Current per I/O Pin: 40 mA
• DC Current for 3.3v Pin: 50 mA
• Flash Memory: 32 KB (ATmega32u4) of which 4 KB used by bootloader
• SRAM: 2.5 KB (ATmega32u4)
• EEPROM: 1 KB (ATmega32u4)
• Clock Speed: 16 MHz

Arduino Leonardo Complete Pinout

PowerSupply:

VIN: The input voltage to the Arduino board when it’s using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.

5V: The regulated power supply used to power the microcontroller and other components on the board. This can come either from VIN via an on-board regulator, or be supplied by USB or another regulated 5V supply.

3V3: A 3.3 volt supply generated by the onboard regulator. Maximum current draw is 50 mA.

GND: Ground pins.

IOREF: The voltage at which the I/O pins of the board are operating (i.e. VCC for the board). This is 5V on the Leonardo.

Input and Output:

Digital I/O:

Each of the 20 digital i/o pins on the Leonardo can be used as an input or output, usingpinMode(), digitalWrite(), and digitalRead() functions. They operate at 5 volts. Each pin can provide or receive a maximum of 40 mA and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms.

Analog Inputs:

A0-A5, A6 – A11 (on digital pins 4, 6, 8, 9, 10, and 12). The Leonardo has 12 analog inputs, labeled A0 through A11, all of which can also be used as digital i/o. Pins A0-A5 appear in the same locations as on the Uno; inputs A6-A11 are on digital i/o pins 4, 6, 8, 9, 10, and 12 respectively. Each analog input provides 10 bits of resolution (i.e. 1024 different values). By default, the analog inputs measure from ground to 5 volts, though is it possible to change the upper end of their range using the AREF pin and the analogReference() function.

Communication

Serial: 0 (RX) and 1 (TX). Used to receive (RX) and transmit (TX) TTL serial data using theATmega32U4 hardware serial capability. Note that on the Leonardo, the Serial class refers to USB (CDC) communication; for TTL serial on pins 0 and 1, use the Serial1 class.

TWI: 2 (SDA) and 3 (SCL). Support TWI communication using the Wire library.

External Interrupts: 3 (interrupt 0), 2 (interrupt 1), 0 (interrupt 2), 1 (interrupt 3) and 7 (interrupt 4). These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value. See the attachInterrupt() function for details.

PWM: 3, 5, 6, 9, 10, 11, and 13. Provide 8-bit PWM output with the analogWrite() function.

SPI: on the ICSP header. These pins support SPI communication using the SPI library. Note that the SPI pins are not connected to any of the digital I/O pins as they are on the Uno, They are only available on the ICSP connector. This means that if you have a shield that uses SPI, but does NOT have a 6-pin ICSP connector that connects to the Leonardo’s 6-pin ICSP header, the shield will not work.

There are couple of other pins in the board:

LED: 13. There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it’s off.

AREF: Reference voltage for the analog inputs. Used with analogReference().

Reset: Bring this line LOW to reset the microcontroller. Typically used to add a reset button to shields which block the one on the board.