Wow - throw back. Someone I know is having an issue w/Teensy 3.1 and WS2801s - but same code, swapping in a Teensy 3.0 works for them. Which meant that I had to dig out WS2801 strips to test and figure out what was going on. Except, it’s been a long time since i’ve used WS2801s. Like a really long time.
Finally, I found an old, mangled strip. Man, i forgot how unwieldy these things were! It’s a 12V WS2801 strip - 3 leds per pixel - I remember being so angry when I got this strip because it wasn’t what I wanted. However, some throwing it around in frustration/annoyance also led to some of the design things that I’ve grown to be fond of in my personal LED projects, so it can’t be all bad.
Still though - 5 wires input to this strip - CLOCK, DATA, GND (for DATA), 12V, GND (for led power). It does feel a bit like a tank, though. Still - glad to not have this be the reality of most of my LED work today. (So looking forward to when I look at WS2811/12s the way I look at WS2801s now)
(For those wondering - the problem appears to be a wiring issue on their end - WS2801 and the teensy 3.1 is happy as a clam over here).