Athom WLED & UCS1903 5050 LED strip: only 3 leds on

Hi everyone,

I try to get an older LED strip to work. It’s a 150 LED strip with UCS1903 ICs on it, which seem to be WS281x compatible from what I googled. It’s 12V and I have a 12V 2A power supply. I use Athom WLED as board. The strip does have a “direction”, I connect it accordingly.

I configured 150 leds in the board and selected WS281x.

Result is that the first 3 leds are slightly on in red & flicker a bit. If I gnd the data line, the other 147 LEDs get bright green (much stronger than the red), which seems to be the default when I just give power and no data.

Any ideas of what I’m doing wrong here?