I am trying to use an atmega32u4 to drive 80 Neopixel 1515's, but I am a little stumped on what to do with my DOUT at the end of my strip. Do I need to connect my final DOUT to anything? The datasheet has a resistor tacked onto the end in their example, but i'm not sure what to make of it. Any help is greatly appreciated.
The text in the datasheet suggests a value between 200-2k for both resistors. One placed between the arduino pin and the first LED and one placed on the last LED between DOUT and ground.
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That's a very bizarre suggestion. 
There should be a 470 Ohm resistor at the point where the data line connects to the first "Din" but an otherwise unconnected resistor hanging off the last "Dout" makes no sense.
If there was a cable running from there to another string of LEDs, a similar resistor at the start of that next string would be a good idea, but otherwise no need whatsoever for a termination resistor on "Dout".