I'm excited to be commissioning a ~CoreXYU + 3x Z-axis for bed leveling. I was hoping to run the 3x Z-axis steppers from the 3HC expansion board, but can't quite get things to work right. G30 functions as expected--the probe lowers to the print bed, triggers the z-probe, stops, sets zero and raises .
However, when I probe the bed with G30 S-1, the probe will again stop the movement, but the z coordinate gets adjusted to some negative value (dive height - zprobe height?), and this negative value is what is returned as the z-probe trigger height.
(Obviously, G30 S-1 is not supposed to adjust the z coordinate. The real deal-breaker is that this same strange behavior occurs during bed probing for leveling / mesh compensation which causes the probe to raise higher and higher each progressive step until it raises outside of the dive height)
I was testing primarily with a BL touch, but the same behavior occurs with a generic switch acting as a probe. Also, the same behavior occurs regardless of whether the z-probe is connected to the main duet3 board, expansion board or tool board.
The Fix: G30 S-1 functions as expected and returns a valid probe height when I moved the 3x z-axis steppers to the main Duet3 board.
This is leading me to think that bed-probing with the Z-axis being driven from any board other than the main board is not supported? Or is there some other bonehead configuration issue that I might have missed?