Arduino Mega Pro 3.3V solderpad
arduino-mega-pro-3-3v / readme.txt
Instructions to have the Mega Pro 3.3V show up in the Arduino device list. 1) Download the latest mega_pro_3.3V zip file and extract it. 2) You will need to be using a recent version of the Arduino environment, version 18 or later. 3) Create a 'hardware' directory inside your sketches folder. If you are using Optiboot, there should already be a hardware folder 4) Copy the mega_pro_3.3V directory into the hardware directory. 5) Restart the Arduino software. New boards will appear in the Tools > Board menu.