If instead Vin/2<3.3, the mosfet is turned on and the USB power is used instead. The 5v generated is then connected to the LP2985 chip which is a voltage regulator that takes in 5v and outputs 3v3. 3V3 is compared to Vin/2 if Vin/2>3V3 then the output is 5v and that is used to turn off the supply from the USB. One of the opamps is used as a comparator and the other is not used at all. Vin is connected to the LM385D chip which contains two op amps. The Vin is direct y connected to the power supply. I still dont understand why there are two voltage regulator chips. The two chips are voltage regulators that produce 5v. The power supply should be between 9v and 15v. If there is a power suply connected to the power jack. There is a USB to serial controller that contains the bootloader which is used to load programs into the ATMEGA328P. There is the power system, that chooses between the power jack and the USB power and produces 5v and 3v3 for the rest of the system. Like every complex system, it is modular. I will attempt to explain how the hardware works as far as I understand it at the moment. How does the arduino work? What does each component do? How does it all come together?
