alt Hacker NewsIf you mean the HW alone... Still over a day. If you mean the software to go along it, a couple orders of magnitude more.
Even the simplest peripherals can bite back if you are not careful and you don't test the edge cases. AVR's are indeed quite simple, but if you try to build stuff other people will use, things need to be polished.
I actually do embedded engineering. I'm doing it right now! More on the SW side than the PCB design side, and, again, this is quite an exaggeration from your side, saying you could do it in a day.
The estimate isn’t right, but the direction is right— there just aren’t that many discrete components on these boards. The chips themselves contain capabilities that an embedded designer would otherwise need to design. I’m not sure there’s much further to go, since much of what isn’t on the chipset is power related.