ErikZalm/Marlin — pull request #192 by daid (2012-06-29 14:38:33+00:00)
Title: Support step motor controllers with active low step pins.

I helped Joris to wire up a Seron 1326 mill to an Arduino with Marlin the other day at Protospace. (To use the large 1220x2440x90mm X/Y/Z as a 3D printer). However, the drivers in this machine required the step signals to be active low, else it refused to step.

I quickly hacked it to work, but now I did a nice solution to make it configurable. We still used to Pololu stepper for the extruder, so I made the setting configurable per axes.