One of the three LED blinky coats is now working.

But there’s no real software on the Arduino yet, just DBU’s demo. And the various controls I plan aren’t in place. Still, it’s been a bear to get this far. The LED strands are physically robust, but electrically very very fragile. I’ve now fried four of them. However, I think I’ve got the handling figured out. Most of the errors were just plain boneheaded, and these things are not forgiving.