Out of curiosity I wanted to check some Arduino board schematics. The Arduino Uno is one of the newest boards and is also quite simple; its open source schematics can be downloaded from here(zip file).
There are two files: a board layout file and a schematics file. They can be opened with the free (but not open source) Eagle software. Eagle is available on Windows and Linux (and Mac too), and in Debian-based distributions (such as Ubuntu) it is available in the package “eagle”.
After launching Eagle, the board layout “
arduino_Uno_ref.brd” can be opened; the schematics file “
arduino_Uno_ref.sch” is opened automatically.
A big part of the schematic is occupied by the two microcontrollers on board: the Atmega328 is the one that can be customized by the user, and the Atmega8U2 converts serial communication to USB. Another important part of the board design is the power management: three different sources of power can be used: the USB cable, the DC connector and an external voltage applied to a pin of the shield.