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See also: Chassis

pr0ncnc is the standard platform that I use to build my CNC microscopes. A typical system consists of:

  • uvscada for high level control
  • AmScope MU800 camera
  • Driver box
    • BBB running machinekit
    • BBB cape w/ optional CD4050 3.3V => 5V boosters
      • XYZ output standard
    • Connected over USB w/ static USB-ethernet bridge IP
    • Case: Hammond 1591-E
    • TODO: standard rubber feet
  • IMS MDrive stepper motors (such as MDrive17 or MDrive23)
  • Linear stages vary
  • Step/direction connectors: Combicon 4 pin
    • TODO: move to mini connectors
  • Where applicable, bipolar motors use Combicon 5 pin
  • Newport 39 mirror mount (tip tilt stage)

BBB bolt pattern

  • WARNING: not square. According to
    • 0.000, 0.000
    • 0.000, 1.900
    • 2.600, 0.125
    • 2.600, 1.775
  • For 4-40 standoffs into case
  • Standoffs are CA glued in
  • Standoffs should not peek out other side
  • Consider putting Kapton on back in case they stick through slightly
  • Need tight fit. Drill size?

Motor connector

Although there is a de-facto DB25 standard for step/direction pulses (from Compumotor?), I don't like DB25 connectors. Instead I use Combicon connectors since I can quickly wire them up and plug/unplug them.

  1. 29 drill for panel mount Combicon bolt holes using 6-32 SHCS

Cable colors

  • Step+: red (left)
  • Step-: black
  • Dir+: blue
  • Dir-: white (right)

BBB 5V cape

Defunct: I now use b3index

Based on CRAMPS pinout

Mcmaster brainscope bbb breakout 5v.png


Pin CPU GPIO CNC function I/O Color
12 gpio1[12] X dir O White
13 gpio0[23] X step O Blue
14 gpio0[26] Y dir O White
15 gpio1[15] Y step O Blue
18 gpio2[1] Z dir O White
19 gpio0[22] Z step O Blue


  • Dir: white
  • Step: blue

I'd like to stick with 5 V CMOS style outputs since all my units can take those

  • Traditional drivers are optocopulers and take resistor limited +/- 5V inputs
  • MDrive17, MDrive23 basically 5-24V open drain but can also operate CMOS

IMS MDrive probably don't take much current (TODO: verify)

My Compumotor M-Drive requires 20 mA min

  • CD4050 can typically only source 3 mA or so
  • HEF4050 can do 20 mA max…borderline
  • Sparkfun BOB-12009 theoretically can do 220 mA

Originally I shied away from the BOB, but think I can simplify the soldering process to make it more attractive

BBB pinout

Mcmaster pr0ncnc p8 pinout.png

Mcmaster pr0ncnc p9 pinout.png

Camera calibration

Put white piece of paper under camera

Run to get RGB values

Adjust V4L controls until balanced

Place V4L control values into microscope.json

  • see example configs for specific usage

Combicon misc

Phoenix combicon combicon pins.jpg

Pin 1 on the left when

  • Female: looking in with round side down

Motor cables

Use 5 pos combicon for bipolar motors (wires: 2 A, 2 B, GND)


  • Molex 1552200235 (Digikey WM15664-10-ND)
  • Phoenix Contact 1786200 (Digikey 277-5776-ND)
  • Phoenix Contact 5448640 (Digikey 277-11353-ND)


  • 6' cables
  • Cut sheath 2" from ends
  • Expose wire 3/8"
  • 3" of heatshrink (think its 1/2")

Pins (ordered by color code):

  • 1 Black
  • 2 Brown
  • 3 Green
  • 4 Blue
  • 5 White

Power cables

Two position combicon

Pins (ordered by color code):

  • 1 Black
  • 2 Red