Weird oscilloscope readings with a digital signal (ws2812)
1) Looks like the current draw and/or sourcing capabilities of the output you are looking at is not matching up. Try just connecting a resistor between output pin and ground to get the current you expect and see how that looks on the scope?

2) It also looks like your oscilloscope probe ground lead is too long (too much induction). See if you can use a short ground connection like this:



That will most likely take care of the "spikes" you see on the scope.