Nine point auto bed leveling enable/disable in gcode  

Nine point auto bed leveling enable/disable in gcode

It's taken me a while to work this one out, so I'm just passing on the information...

I had 'one.gcode' that did the 9 point auto bed leveling, and I had 'two.gcode', that didn't do it. I wanted to know what made one do it but the other not. I was expecting to find a particular G or M code that made it do it, and although there is one (either G80 or G81 - I can't remember now), neither of these where present in either file!

After trawling through the source code, I eventually found the answer.

If you home all axis together using:
G28
then the the machine finds the home positions, then runs the 9 point bed leveling gets run.

But if you home just some of the axis, or split the homing over two lines like this:
G28 X0 Y0
G29 Z0
then it just homes the axis that you specify.