M19 for Indexing a Spindle using Stepper Motors

I am trying to use the M19 command:

m19 r90 q10 p1 $0

The m3 & m4 commands work as expected, but m19 does not.  Any guidance would be greatly appreciated.

My HAL and INI files are attached (Spindle0.inc renamed to be Spindle.inc.ini so that it could be attached).

www.linuxcnc.org/docs/html/gcode/m-code.html#mcode:m19

Says:

Spindle orientation requires a quadrature encoder with an index to sense the spindle shaft position and direction of rotation.

The need for an encoder can be worked around by using a StepGen with the index feature but that would still require
a once per turn signal for initial alignment.

Thank you Peter.  I reviewed the link you provided, but is there a document or manual which describes how to set this up?