> > And using the 74595 to expand my I/O capabilities and because then I can send the > > values received in from MAME straight to the chip, no conversion needed. > > If you drive the 7-segment directly from Ardino GPIO you don't need to convert the > values. That's the entire reason I said to do that.
He won't have to convert the values if he uses the 74595 either. You missed that he wants to do it as an exercise in driving an external shift register. It makes a bit more sense now.