The Arduino Uno Rev3 SMD is a microcontroller board built around the ATmega328 chip. It features 14 digital input/output pins (6 of which support PWM output), 6 analog inputs, a 16 MHz ceramic resonator (CSTCE16M0V53-R0), a USB connection, a power jack, an ICSP header, and a reset button. The board includes all the essential components to run the microcontroller, making it easy to get started by connecting it to a computer via USB or powering it with an AC-to-DC adapter or battery.

What sets the Uno apart from earlier boards is the absence of the FTDI USB-to-serial driver chip, offering a different approach to USB communication.

The R3 version introduces several enhancements:

• The ATmega16U2 replaces the 8U2 as the USB-to-Serial converter.
• A revised 1.0 pinout adds SDA and SCL pins for TWI communication near the AREF pin, along with two additional pins near the RESET pin: IOREF, which enables shields to adapt to the board’s voltage, and a reserved pin for future use.
• An improved RESET circuit for greater reliability.