"Gunner Asch" wrote in message
...
On Mon, 18 Jul 2011 07:33:00 -0700, "Bob La Londe"
wrote:


All that being said, It might be hard to find a laptop that runs Windows
quickly and reliably, has appropriate ports for your hardware (Usually an
LPT port),

USB to just about any sort of output..serial, parallel etc etc are
commonly available at any computer shop

LOL. Yeah right. Try running a stepper driver off of one. Oh, yeah and
make sure its got high enough voltage on all the outputs. They don't work.
We aren't talking about sending data whenever it feels like to a printer
that buffers it. We are talking about continuous precisely timed signals on
multiple outputs simultaneously thousands of times per second.

A 4 axis stepper controller or four single stepper controllers can run off a
single TRUE parallel port. All four of those axis could potentially be
moving at 60 inches per minute (I capped them at 45) on one of my little
machines at the same time. To do that in any form of coherence to get a
good result it needs precise timing and both step and direction signals for
each of those four axis. The Taig takes 40,000 steps per inch. The MaxNC
with the screws I use takes 32,000 steps per inch. 32,000 X 2 X 45 X 4.
That is a lot of precisely timed signaling. Sure they are simple single
data item signals, but there are a bunch of them and they all hit the
controllers which step the motors just right. In addition there are other
input and outputs that are used for limit switches, spindle control,
external e-stop, etc.

A true honest to goodness hardware parallel port can do it on a good
computer. I just finished a mold plate that ran over a million lines of
code to cut using one. (Actually the finish pass alone was over a million
lines of code)

From what I understand the SmoothStepper works directly with the software
and handles the timing externally from the PC removing a tremendous load
from the CPU and improving overall performance.