Datasheet

jack) to your computer. The programming port uses the 16U2 as a USB-to-serial chip
connected to the first UART of the SAM3X (RX0 and TX0). The 16U2 has two pins connected
to the Reset and Erase pins of the SAM3X. Opening and closing the Programming port
connected at 1200bps triggers a “hard erase” procedure of the SAM3X chip, activating the
Erase and Reset pins on the SAM3X before communicating with the UART. This is the
recommended port for programming the Due. It is more reliable than the "soft erase" that
occurs on the Native port, and it should work even if the main MCU has crashed.
Native port: To use this port, select "Arduino Due (Native USB Port)" as your board in the
Arduino IDE. The Native USB port is connected directly to the SAM3X. Connect the Due's
Native USB port (the one closest to the reset button) to your computer. Opening and closing
the Native port at 1200bps triggers a 'soft erase' procedure: the flash memory is erased and
the board is restarted with the bootloader. If the MCU crashed for some reason it is likely that
the soft erase procedure won't work as this procedure happens entirely in software on the
SAM3X. Opening and closing the native port at a different baudrate will not reset the
SAM3X.
Unlike other Arduino boards which use avrdude for uploading, the Due relies on bossac.
The ATmega16U2 firmware source code is available in the Arduino repository. You can use
the ISP header with an external programmer (overwriting the DFU bootloader). See this
user-contributed tutorial for more information.
The Arduino Due has a resettable polyfuse that protects your computer's USB ports from
shorts and overcurrent. Although most computers provide their own internal protection, the
fuse provides an extra layer of protection. If more than 500 mA is applied to the USB port,
the fuse will automatically break the connection until the short or overload is removed.
The maximum length and width of the Arduino Due PCB are 4 and 2.1 inches respectively,
with the USB connectors and power jack extending beyond the former dimension. Three
screw holes allow the board to be attached to a surface or case. Note that the distance
between digital pins 7 and 8 is 160 mil (0.16"), not an even multiple of the 100 mil spacing of
the other pins.
The Arduino Due is designed to be compatible with most shields designed for the Uno,
Diecimila or Duemilanove. Digital pins 0 to 13 (and the adjacent AREF and GND pins),
analog inputs 0 to 5, the power header, and "ICSP" (SPI) header are all in equivalent
locations. Further the main UART (serial port) is located on the same pins (0 and 1). Please
note that I
2
C is not located on the same pins on the Due (20 and 21) as the Duemilanove /
Diecimila (analog inputs 4 and 5).