Optical encoders with DC motors

Hi to all,
lately I am playing with optical encoders and DC motors, all taken from old printers.
With arduino I have full control over them. I also implemented a digital PID to control their position.
Now I would like to use them with LinuxCNC.
As I have read here LinuxCNC has the capability to work with encoders (see linuxcnc.org/docs/ja/html/man/man9/encoder.9.html)
but I don't understand some things at this point:

1. What hardware do I need to feed the input signals of the encoders to the parallel port and ouput suitable signals for the H-Bridges to control the DC motors (1 PWM and 1 Direction signal per motor).
2. How to configure the software to run these motors. Should I trim the PIDs inside LinuxCNC for each axis/motor?
3. Is there a way to use my hardware measured position (from arduino) and feed this info to LinuxCNC?
4. Can I use arduino as a form of servo motor and send position commands to it through LinuxCNC? I know by this way is not actually a complete closed loop system as LinuxCNC will not have the primary feedback of the position.

Any help would much appreciated

Answering my own question, I found the following related infos:

www.forum.linuxcnc.org/27-driver-boards/...ncoders-and-h-bridge
emergent.unpythonic.net/projects/01142347802
www.forum.linuxcnc.org/49-basic-configur...tch-servo-for-3-axis

So looks like it is possible for 2 and maybe even 3 axes.

Hi tommylight, this is exactly what I want to do. I also found this board in ebay and considering buying it.
How did you produce the PWM and DIR signals from LinuxCNC? Do you have any code you could share with us?
Have you tried any modifications to introduce a 3rd axis or you spent all the I/O of the parallel port?
Have you connected the optical encoders directly to the parallel port? If so how, through simple resistors or through optocouplers?
Why not use this board instead of yours www.ebay.com/itm/Double-BTS7960B-DC-43A-...6:g:vgYAAOSwWyRarJJa, is this only for one motor?

Hi guys, yesterday I had a huge progress!
Using the etch servo example and a single L293D chip on a breadboard connected to the parallel port I managed to control the head of a printer successfully (normal dc motor with linear optical encoder). Trimming the PID was the most difficult part of the story, but yeah it works!!
LinuxCNC is amazing, it can do everything!!
Now I need to research if I could make 3 axes instead of normal two ones described in the example...

@tommylight thanks for the tip for "mode X". I didn't know it was existing. Right now I have configured BIOS to "EPP" but I checked and there is "Bi-Directional" mode which I suppose is the "mode X".

Theoretically to make a 3 axes cnc I need 9 inputs and at least 6 outputs:
2 Inputs per channel for optical encoders, 1 Input per channel for Home switch and 2 Outputs per channel (one for direction and one for pwm).
The current "etch servo" requires 3 outputs per channel to drive the L293D (or the L298) so I will need extra HW logic to convert the signal to two per channel. Right now etch-servo requires 9 outputs and "mode X" gives only 8 outputs...

In mini 3 axis you can connect all
3 motor enable signals together.= -2 outputs.
3 home switches together when homing one axis after another. = - 2 inputs.

And here is a video of my implementation.
Two axes in closed loop with a single chip and a PC. Amazing!

In mini 3 axis you can connect all
3 motor enable signals together.= -2 outputs.
3 home switches together when homing one axis after another. = - 2 inputs.

What do you mean "mini".
Enable signals are usually needed for PWM control. I don't think we can connect them together.
If we put the home switches in series (if I understood correctly your idea) then until the last axis is homed there will be force on the rest axes, something not good!

3axis is a small machine (xyz). Up to 9 are possible.

If you want to stay on position, your motors must stay under power as long as you want to do something soon = enable on. All my drivers (3 machines) are always connected to the same output. ( Enable, step, dir).

Lcnc is easy to setup having several home switches in series or parralel to make sequential homing. Well documented in the html...