Tiny Controls · Own design
Parallel Port Break-out Board (PP-BOB2-v2)
Parallel port breakout board for CNC, with buffered step/direction outputs for 4 axes plus an X-slave, three relays, an isolated spindle PWM output and a jumper-set charge pump.
Overview
The PP-BOB2-v2 sits between a PC's parallel port and a CNC machine, turning the port's DB-25 signals into screw terminals a machine can actually be wired to. It works with Mach3, TurboCNC, EMC2 and KCam.
Step and direction outputs cover 4 axes plus an X-slave, with the X-axis output buffered twice and brought out on two separate connectors — the arrangement a gantry machine needs, where two motors share one axis. All outputs are buffered and land on screw terminals rather than the bare DB-25 pins, and can be wired pull-up or pull-down, with the motor-common signal set high or low, by jumper.
Three onboard relays and an isolated PWM-to-0-10V output handle spindle switching and speed reference without routing that signal back through the PC's ground. An onboard charge pump, jumper-configurable from 200 Hz to over 15 kHz, holds the outputs disabled unless it sees a live signal from the PC — a stalled or crashed PC does not leave the machine running. The charge pump can be switched off and its output repurposed as a general-purpose signal if it is not needed. Every input and output has an LED indicator, so a wiring fault shows on the board rather than only in software.
It runs from 24 V DC, draws up to 0.5 A, and measures 135 x 95 mm at 40 g.
This is the current version — the PP-BOB2-v1 it replaced ran from 12 V DC and is discontinued.
Designed and built by Tiny Controls in India.
Specifications
| Axes | 4 |
|---|---|
| Digital outputs | 14 |
| Supply voltage | 24 V DC |
| Axis drive type | Step / Dir |
| Digital inputs | 5 |
| Analog output | 0-10 V isolated |
| Relays | 3 on board |
| Max power consumption | 0.5 A at 24 V |
| Weight | 40 g |
Downloads
Questions
I have a gantry with two motors sharing one axis — can this actually drive both?
Yes — the X-axis output is buffered twice and brought out on two separate connectors, specifically for that gantry arrangement.
What CNC software does this actually work with?
Mach3, TurboCNC, EMC2 and KCam.
If my PC crashes mid-job, will the machine keep running unattended?
No — an onboard charge pump holds the outputs disabled unless it sees a live signal from the PC, so a stalled or crashed PC doesn't leave the machine running.
I don't need that charge pump safety feature — can I repurpose that signal for something else?
Yes — it can be switched off and its output repurposed as a general-purpose signal.
What's actually different between this and the older PP-BOB2-v1?
Supply voltage mainly — the v1 ran from 12 V DC and is now discontinued; this is the current version, running from 24 V DC.