WS2812B data line interference

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Hi,

Yesterday I experimented with some WS2812B (aka Neopixels) on a breadboard. Although it was working, it was also extremely sensitive to interference, e.g. a finger anywhere near the data line, or a scope probe connected to it, caused enough interference to completely ruin the signal, resulting in either unintended commands or no commands reaching the WS2812Bs.

I've read up a bit and apparently it is recommended to have a 100nF capacitor between Vdd and GND on each unit, but I don't see how that would help with the interference issue, though I will try. I have a design in mind that will require about 50 units mounted on a circular PCB (yeah, it is also a clock) and I'm worried that I'll run into similar issues on a PCB.

So, my question is this: what can I do mitigate interference to these units? A ground plane is given, and the 100nF caps, but what else? Also, should I do something to mitigate interference from these units, for example if I have an I2C bus on the same PCB?

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Hm, putting a 100nF cap between data and GND seems to have soleved it, at least on the breadboard with only three units. Still, I would love to get some input on what else I can/should do.