What you are probally looking for is
http://www.ifirobotics.com/docs/oi-r...de-2-21-05.pdf , specifically pages 7-10 which tell you which ports have which connections. There are a total of 16 digital inputs, and 16 analog inputs. This sort of limits you to 16 switch inputs (if it is a DPST ON-OFF-ON toggle switch, and you want to use both ON's, you need 2 inputs), although we usually have more than that by using resistor networks on an analog (same way the hat works on an analog joystick).
Hope this helps.