We learned a lot from NeuroBytes v0.8. Version 0.9 kept the same general shape but improved a number of items. It also suffered from numerous design failures, warranting the creation of NeuroBytes v0.91 within days of its arrival from the fabricator.
NeuroBytes v0.9 added an on-board low-dropout 5VDC regulator, a level adjustment potentiometer, and a blocking diode on the back side of the tantalum reservoir capacitor. The regulator allowed the circuit to operate at 6VDC, and this feature combined with the blocking diode solved the servo hot-swap brownout issue that plagued v0.8. The board itself was slightly larger (by ~3mm) to acaccommodate the new components, and the two ends were slightly tweaked to ensure parallelism so the design could be tab-routed. Other improvements included a ton of I/O test pads, less tiny text on the silkscreen, and a more durable pushbutton.
First problem, shown above: I connected the potentiometer to one of the analog comparator ports rather than an ADC input. Silly mistake, and it meant the component did nothing but get easily stripped out by anything other than a delicate plastic screwdriver. Not a good start.
Second problem: the AXON2-SIG line shorted to VCC. Another dumb mistake; I moved the pad at the last minute, didn't see the overlap, and didn't run a final DRC. I was able to slice the track for testing, but before doing this the microcontroller actually heated up a bit which was concerning to say the least.
Everything else, including the programming/test rig shown above, worked well enough. The new pushbutton is IP67 rated and feels great; we had a few failures with the right angle version so I nixed it in favor of something a bit more traditional. But the other issues meant this version didn't last long before moving aside for v0.91.