NANO shield and UNO multi-purpose expansion board for arduino nano 3.0 1 IO port leads all digital and analog IO ports, each IO port has positive and negative power supply interface standard (2) leads to an I2C interface on the motherboard , convenient and I2C devices connected 3 . Increasing the DC power connector . NANO USB interface board supply current is actually only 50MA, to bring high-current devices, such as when the steering is obviously insufficient , this time in the DC power supply interface provides external power to ensure the stability of equipment operation .