Reading in Square waves

Hi I have an idea Im bouncing around about using the pulseIn() function to read in square waves that I'll play from my ipod. Is this possible to do using a digital pin on the arduino. I know that the ipod would compress the square wave. Is there any way of playingback square waves from an Ipod and have the arduino reconize it? Thanks Randall

A square wave contains an infinite number of harmonics therefore what you get out of your iPod will not look square but a bit more ragged.
You can clean it up by feeding the audio output into a comparator like the LM393 before putting it into the digital input.

Can someone please help me with a schematic on how to wire this lm393? Any help would be greatly appreciated