Neopixels are cool but the timing to drive them sucks up a lot of processor cycles and/or RAM.
In this video I figure out a way to build an adapter to drive them with a standard SPI bus at exactly 3 bytes per pixel freeing up loads of resources.
Updated schematic: https://github.com/benheck/SPI-Neopixel
Uses a quad NOR IC now, giving us the logic to have an active low chip select allowing other things to be used on same SPI bus.