The Arduino Uno is a microcontroller board based on the ATmega328 (datasheet
). It has 14 digital input/output pins (of which 6 can be used as
PWM outputs), 6 analog inputs, a 16 MHz ceramic resonator, a 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 a
AC-to-DC adapter or battery to get started.
The Uno differs from all preceding boards in that it does not use
the FTDI USB-to-serial driver chip. Instead, it features the
Atmega16U2 (Atmega8U2 up to version R2) programmed as a
Revision 2 of the Uno board has a resistor pulling the 8U2 HWB line to
ground, making it easier to put into DFU mode.
Revision 3 of the board has the following new features:
- 1.0 pinout: added SDA and SCL pins that are near to the AREF pin and two
other new pins placed near to the RESET pin, the IOREF that allow
the shields to adapt to the voltage provided from the board. In
future, shields will be compatible with both the board that uses
the AVR, which operates with 5V and with the Arduino Due that
operates with 3.3V. The second one is a not connected pin, that is
reserved for future purposes.
- Stronger RESET circuit.
- Atmega 16U2 replace the 8U2.
"Uno" means one in Italian and is named to mark the upcoming
release of Arduino 1.0. The Uno and version 1.0 will be the
reference versions of Arduino, moving forward. The Uno is the
latest in a series of USB Arduino boards, and the reference model
for the Arduino platform.