These configurations drive a standard 4-axis 3D printer using the PRU
for high speed step/dir pulse generation and work with the following
hardware:

  BeBoPr++
  BeBoPr+
  BeBoPr with Bridge
  Other boards using the somewhat standard BeBoPr-Bridge pinout

If using a BeagleBone Black, you may leave the eMMC and HDMI interfaces
enabled.

Configuration Details
=====================
Adjust as required for your machine.  Make scale negative to invert any
axis that is moving 'backwards'.

BeBoPr-Bridge: 
--------------
A typical "MendelMax" style printer

lineardelta:
------------
A linear delta or "Rostock" style printer


lineardelta-vel-extr:
---------------------
A linear delta printer using dynamicaly calculated velocity control of
the extruder, rather than operating as a coordinated 4-axis machine.

For detalis, see:
http://basdebruijn.com/2014/05/machinekit-and-additive-manufacturing/

