Hi Carl,
Well although you may have a point there dont we have to consider that he was starting out with a 555 for an AD converter? Wouldnt that be a somewhat similar way? Or maybe you are saying that is too hard to understand too...in that case i would go for the simplest which is a voltage divider and set of comparators. But it appeared to me that he wanted to understand the way the 555 does it or similar, but then other people started suggesting other converters.
If it's the simplest possible converter than i would say a resistor divider and set of comparators, but that is gong to be nothing like how the 555 works for A to D.