On this UNO R3 MEGA328P CH340 USB Development Board, there is TWI interface and the IOREF in the top and bottom connectors.
This change keeps the board 100% compatible with the current boards and shields, but adds possibilities for new shields.
Reset button moved from center of board to corner near USB connector. This is great; makes it much easier to access with a shield on. Larger heat sinking copper area for the LM117 regulator.

Description:
Optimizing the UNO item, and it can be compatible and stable used in both Win7 and Wind8Add two rows of the holes for the pins.
So it can be connected with normal Dubond lineAdd 3 rows of the holes for wiringChange the in-line package of ATMEGA328P to flat packagePlug UNO development board
and the driver will be automatically installedSelect the board UNO inside the dieSelect the COM port (this can be in my computer queries) , just inside your uno port development boardYou'd better to choose arduino own routine procedures, burn into the board

Specifications:
Microcontroller:  ATMEGA328PUSB chip:  CH340GInput voltage - 7-12V14 Digital I/O Pins (6 PWM outputs)6 Analog Inputs32k Flash Memory16Mhz
Clock SpeedSize: 7.5 x 5.4 x 1.7cm (L x W x H)Package included:
1 x UNO R3 MEGA328P CH340 Development Board1 x USB cable