de2 fpga gpio question

edit: did more reading and figured out exactly what i want to say.

i have an adc that is 12 bit. i want to interface this to the fpga using either the gpio or something else. i don't want to use additional hardware so i was wondering what's the best way to this on the de2. i'm going to use the nios ii to play around with the signal once it gets it. it's going to be like a real time system that gets the output from the adc, then the fpga does some computing and lights up some lights or turns something on.