• Microcontroller 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 16 MHz
• 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.