But, at some point, every NeoPixel'er bumps into the constraints of that single-

data-wire: the timing is very picky and often time your code has to stop

completely so that it can burst out the data without any interruptions. This

requirement makes it tough to create fast-update lighting effects, and limits the

number of pixels you can drive before other hardware peripherals get attention.

Resident pixel-pro Paint Your Dragon (who coined the name NeoPixel dont-cha-

know!) took on this challenge and has succeeded gloriously. By carefully

examining the ATSAMD21 datasheet he noticed you could use the Timer 0 in

'waveform' mode, and create 8 unique waveforms over DMA that would handle

all the pixel-pushing for you.

Thus is born the NeoPXL8 Arduino library and NeoPXL8 Featherwing! The library

runs on our Feather M0's (the Basic Proto, Adalogger, Bluefruit, Express, and

others) and handles all the NeoPixeling for you, up to 8 strands of concurrent

DMA output each one can be 250 pixels long for a total of 8 x 250 = 2000

pixels. That leaves you some RAM for your code to run in as well - the

theoretical max is 340 pixels per strand but you'd be using all the RAM on the

M0 chip.

To make connection easy, this Featherwing does the level-shifting and pin

arrangements for you. All 8 strands have a level shifter that converts the 3.3V

logic level to 5V logic, there's a little switch-cap converter that generates the

clean 5V power supply for you. Then a 100 ohm resistor in line after the buffer

reduces ringing on long wiring runs.

You get two options for connecting NeoPixels:



2 x 8 Header with ground and 5V-logic signal, in pairs



2 x RJ-45 'Ethernet' Jacks, with ground and 5V-logic signal per twisted

pair. This matches the same wiring as the OctWS2811

To keep the 'Wing compact we let you choose which wiring you'd like to go with,

just solder in the connectors you prefer. Then you'll also need to provide power

to the NeoPixels. Since you'll need many Amps of current, we don't manage that

through the Wing - the PCB copper would be too limiting. We recommend

using terminal blocks or bus bars to connect all the ground/5V power wires

together and powering them from their own chunky 5V supply.