[Emc-users] RepRap RAMPS stepper controller board with LinuxCNC?

[Scott H. <sco...@gm...>]

All-

I am starting in with some experiments using the RepRap RAMPS board (
http://reprap.org/wiki/Arduino_Mega_Pololu_Shield) (basically a 3-5 axis
small stepper driver board with additional heater outputs and temperature
inputs), but instead of using an Arduino with firmware like sprinter for
controlling it, I plan to use LinuxCNC with a parallel port.  To that end
I've acquired an Intel 525MW board and am so far very pleased with it.  To
adapt a parallel port to drive the RAMPS board, I plan to make a small
circuit board with the same footprint as the Arduino shield that would
normally driver the RAMPS board, but route the parallel port pins instead.

I am expecting this will generally be fairly straightforward, and there is
just barely enough parallel I/O to be workable, but I have a few questions
that I thought I would run by you all:

1) Many of the output pins are step/dir which of course will require real
time control, but others things like heater outputs, etc, that would not
suffer too much from latency.  Has anyone used a latching shift register
for extending parallel port output when latency is less of a concern?

2) I've gotten some basic encoder-based frequency-based analog input
working in other scenarios (
http://code.google.com/p/sector67-sandbox/wiki/FrequencyBasedAnalogInput)
and plan to use that for the analog temperature inputs on the parallel port
if feasible.  Does that seem reasonable?

3) Has anyone else done anything similar to this?  I've followed the
http://reprap.org/wiki/EMCRepRap effort, but that doesn't use the RAMPS
board.  I expect the user interface and gcode translation tools from that
project to be useful.

Thanks,

Scott