Wall … Head … BANGING! I spent days chasing this, thinking I had an issue with my custom controllers. The past two days I spent completely redoing the design, moving traces around, in case I had electrical interference. Then tonight I decided to move everything back to the test rig I’ve been working on since day one, the one on a breadboard. Much to my surprise the problem persisted. It was working fine before. So what changed?
Then it hit me! The last thing I did with FastLED was abusing a tiny85 and following a suggestion from @Daniel_Garcia I installed the dithering branch of 2.1. Could that be it? I rolled back to 2.0 and the problem disappeared. Re-installed the 2.1-dithering branch and sure enough, there’s the problem again.
Moral of the story: if you’re testing out different versions of the library, REMEMBER THAT when you suddenly encounter a problem.
The pictures below show what the effect is supposed to look like, and what it looks like with the 2.1-dithering branch. The non-dithering doesn’t do this, but there are other odd things happening with one of the effects that’s supposed to cycle through the full hue range, but instead it only cycled between red and white. Another effect has trouble with lower values (some show up, some don’t.)
I’m back on 2.0 and everything works.