This regulator also provides the power supply to the SAM3X micro controller. A 3.3 volt supply generated by the on-board regulator. Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). This pin outputs a regulated 5V from the regulator on the board. You can supply voltage through this pin, or if supplying voltage via the power jack, access it through this pin. 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). If using more than 12V, the voltage regulator may overheat and damage the board. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. The board can operate on an external supply of 6 to 20 volts. Leads from a battery can be inserted in the Gnd and Vin pin headers of the POWER connector. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The power source is selected automatically. The Arduino Due can be powered via the USB connector or with an external power supply. An unconnected pin, reserved for future use. This enables shield compatibility with a 3.3V board like the Due and AVR-based boards which operate at 5V. The IOREF pin which allows an attached shield with the proper configuration to adapt to the voltage provided by the board. TWI: SDA and SCL pins that are near to the AREF pin.The Due is compatible with all Arduino shields that work at 3.3V and are compliant with the 1.0 Arduino pinout. The board contains everything needed to support the microcontroller simply connect it to a computer with a micro-USB cable or power it with a AC-to-DC adapter or battery to get started. Providing higher voltages, like 5V to an I/O pin could damage the board. The maximum voltage that the I/O pins can tolerate is 3.3V. Warning: Unlike other Arduino boards, the Arduino Due board runs at 3.3V. It has 54 digital input/output pins (of which 12 can be used as PWM outputs), 12 analog inputs, 4 UARTs (hardware serial ports), a 84 MHz clock, an USB OTG capable connection, 2 DAC (digital to analog), 2 TWI, a power jack, an SPI header, a JTAG header, a reset button and an erase button. It is the first Arduino board based on a 32-bit ARM core microcontroller. The Arduino Due is a microcontroller board based on the Atmel SAM3X8E ARM Cortex-M3 CPU ( datasheet).

Due wire library