stepper motors nema 17 with encoder

[Marta]

Hi, I would like to contro 4 stepper motor nema 17 with encoder through a PMDX-126 Breakout Board. I would like to use encoders only to save position data in a file. Not for feedback.
In the comparison table (http://www.pmdx.com/BreakoutFeatures) I see that PMDX-122 Breakout Board allow to connect encoder as an input and receive 8 Data bit inputs, while PMDX-126 need a PMDX-108-Input. Anyway in the PMDX-108-Input manual it is not clearly specified if it is possible to connect encoders.
PMDX-126 Breakout Board can be interfaced with a lot of accessories, so I prefere this one to PMDX-122.
Someone known if it is possible to connect somehow (by PMDX-108-Input or others) the encoders to PMDX-126 Breakout Board?
Thank you.

[Steve Stallings]

First of all, you will need software that can receive and make use of
the encoder data. Mach3 and its parallel port driver can read encoders
as MPGs. You would need to add macros or brains to save the data.

The inputs of a PMDX-126 or PMDX-108 will work with encoders
provided the signal frequency is not too high. This should not be a
problem with a stepper driven system.

The PMDX-126 provides a maximum of 8 input signals. Each encoder
needs two signals, or three if you want to use the index. This will
limit the number of encoders and/or home and limit switches available
unless a PMDX-108-Input or a PMDX-122 are added.

In all cases, you will need an additional parallel port or a device such
as a SmoothStepper which emulates two parallel ports.

[Bob at PMDX]

I have to ask what kind of position data you want saved?  Both Mach3 and Mach4 will save the current motor positions (as displayed on the DROs) when you exit, and will restore those positions to the DROs when you re-start Mach3/Mach4.

If you want some kind of waypoint data stored during operation, that can also be obtained by having some code (macro or brains in Mach3, or Lua in Mach4) periodically read the DROs and write the data to a file. In Mach3 and Mach4, the DROs are updated from the motion device to reflect the actual position.  That is presuming that none of the motors have stalled.

Bob