[Martin Hubáček] wrote in with his WS2812 LED library for the STM32F3 series processors. [Martin]’s library takes the same approach as [Paul Stoffregen]’s OctoWS2811 for the Teensy, and [Erich Styger] ...

then one of two things is your problem: 1) you have ata33 cables. if your cables are black on both ends, this is likely the case. 2) your ata66/100 cables are installed backwards. the colored end ...