Using ATMega 16U2 microcontroller。 - Micro controller: ATmega328; - Operating Voltage: 5V; - Input Voltage (recommended): 7-12V; - Input Voltage (limits): 6-20V; - Digital I/O Pins: 14 (of which 6 provide PWM output) - Analog Input Pins: 6 - DC Current per I/O Pin: 40 mA - DC Current for 3.3V Pin: 50 mA - Flash Memory: 32 KB (ATmega328) of which 0.5 KB used by bootloader - SRAM: 2 KB (ATmega328) - EEPROM:1 KB (ATmega328) - Clock Speed: 16MHz - Stitching changes: beside the AREF sutural are two extra I2C pins (SDA and SCL which are copy of Analog 4 and 5 not additional I2C interface). Beside the RESET also are two extra pins one is IOREF which supports the extension board stand load voltage. The stitching just shows extension board the current on-board voltage. The other one is backup placeholder pins. The RESET circuit is more stable. RESET button position is changed and moved to near the USB interface of voids which is more convenient. ATmega16U2 replaced 8U2 but it does not mean that the 16k flash of R3 can make your code run faster. This upgrade works to the USB interface chip which enables UNO simulate USB HID in theory such as MIDI/Joystick/Keyboard. Motor drive expansion board for Arduino 2 x 5V servo motors (servos) port connected to the Arduino's high-resolution high-precision timer - no jitter; Up to four bi-directional DC motor and 4-channel PWM speed (about 0.5% resolution); Up to 2 stepper motor control single / two-step control staggered or micro-step and the rotation angle control; 4-channel H-bridge: L293D chip every road and bridge to provide .0.6 A (peak 1.2A) current and with a thermal power protection 4.5V to 36V; Pull-down resistor to ensure that the motor remains stopped on power; arge Terminal terminals make it easier to wire (10 - 22AWG) and power; With the Arduino reset button; 2 terminal external power supply terminal to ensure the separation of logic and motor drive power; Compatible with Mega Diecimila & Duemilanove; Download easy-to-use Arduino software library rapid project development