The biggest different from Arduino UNO is USB to serial port part, which use ATMega16U2 microcontroler Specification: Pin change: add two I2C pin (SDA, SCL, just a copy of analog 4 and 5); Ass two pins next to Reset, one is IOREF, which let expansion board suitable for on-board voltage, the other is for spare; Reset also moved to next to USB port; A8U2 is replaced by Tmega16U2, which id for USB port chip, let UNO analog USB HID, such as MIDI / Joystick / Keyboard Application: Learning set

The biggest different from Arduino UNO is USB to serial port part, which use ATMega16U2 microcontroler Specification: Pin change: add two I2C pin (SDA, SCL, just a copy of analog 4 and 5); Ass two pins next to Reset, one is IOREF, which let expansion board suitable for on-board voltage, the other is for spare; Reset also moved to next to USB port; A8U2 is replaced by Tmega16U2, which id for USB port chip, let UNO analog USB HID, such as MIDI / Joystick / Keyboard Application: Learning set