A few design tweaks and many hours of routing later, Flounder Rev 1.0A is ready for manufacturing. Other than rearranging some of the connectors, the most significant changes are the reworked power supply. I removed the heatsink and mounted the regulator to the board directly. I also added in screw terminals for voltage in, voltage out, and the power switch. When I build a case for this board, I'll need dedicated connectors for those.

At first I was debating trying to get away with a two-layer PCB, but I quickly decided against it. I think there would have been room to route the power and ground cleanly enough, but the price difference to upgrade to a four-layer board is about $30. The ease of routing and the better signal integrity seems worth it. The one "compromise" I made was using 1206 SMD parts for all of the resistors and decoupling capacitors. They're all on the back of the board.

Although there are a few signals that I did not use in this design, I made sure not to short anything directly to ground or 5v. Unused outputs were left unconnected and unused inputs were all connected to the appropriate level via a pullup or pulldown resistor. I've made been lazy about that in the past. Shorting signals directly to 5v or ground makes it much more annoying to bodge in a fix.

Time to sleep and review the design tomorrow. If I don't find any issues in the morning, I'll be sending the board off for manufacturing.