foolcoffee doubleclock

I had a Digital Computers course where we had these logic design and implementation lab classes. We had to implement various modules in Verilog and run them in a low-end FPGA. But during the first lab we weren't yet familiar with Verilog, so we were supposed to enter a digital schematic graphically. The schematic was designed the hardcore, old-school way, by building a state machine on paper, assigning bits to states, writing equations, translating them to flip-flops and gates et cetera. The state machine was for a (famous with past and current students at our faculty) "coke vending machine". It never worked as supposed and I suspect (being too lazy to prove though) that the equations suggested in the lab documentation were wrong. Years have gone by and, while having a break in the faculty hallway, I found that maybe one of our graduates, now employed at a vending machine company, has finally got it working: