I'm having trouble with a circuit I'm building using WS2812b LEDs. The 41 LED pixels are connected to the D3 pin of a Wemos D1 Mini. They are powered by a sufficient strong power source, with a power injection after 20 LEDs.
Actually, they work great. At least, they do when they're supposed to show a single color at full brightness. But when I dim them, even just one or more, they start flickering at random places. Same when I light a few leds instead of all of them.
I'm using the FastLED library. I've had succes before without using a level shifter.
Any idea on what's going on?