Wow, I had to convert between 4 or 5 coordinate systems to finally get the images proper... There's the cartesian coordinates of the image itself, that have to be scaled to fit within the "window" on the diskette... There's the polar coordinates, in real-life (mm, radians)... There's conversion from mm to "steps" of the steppers... Then since the vertical motor homes at the top, rather than the bottom, there's a strange sort of "polar coordinates" used for actually moving the steppers... So rather'n a radius and an angle, we have a distance from top, and an angle. Confusing.

Anyways, broken down into steps it's not *that* complicated, but there was *plenty* of room for error, and amazingly didn't run into any math/conceptual/code-errors in those conversions. OTOH there was a stupid oversight at the very end during the drawing-routine, and there's some work to be done with making sure the image fits within the "window" that can physically move around, and the fact that the disk itself doesn't fill up the entire window... For now, simply make sure the image drawn has a blank border...

It definitely makes a huge difference converting to polar... A couple images done when I treated it as rectangular can't even be discerned... So there's that huge improvement.

Also, I think the vertical motion repeatability problem was largely due to a few factors: A) I was trying out running the 5V side of the H-Bridge at 3.6V (to match my microcontroller), which seemed to work fine for quite some time, but switching to 5V seemed to help the repeatability quite a bit. B) It was mounted somewhat vertically, and I think some of the missed steps might've had to do with the weight. C) There was the "slop" in the rotational-"engagement" mechanism... I put a couple rare-earth magnets on the rotational-mechanism to hold the disk tight, and it seems to have helped.