I want to use the layout of the Arduino Leonardo for my project. I've downloaded the .zip file and opened it with EAGLE, but there's something in the schematic I do not understand:
What do R2 and R3 do? And why is their value NM? Whats the difference between AGND, UGND and GND?
NM = not mounted? Check the pictures, see if they are installed.
Lets you keep the Analog Ground seperated from the USB Gnd for quieter analog operation.
All grounds should end up connected at one place, see iif you can follow them on the .brd file.