Re: Andy Olney's Comments on PIC-Servo

> From: "Andy Olney" <aolney@...>
> I am guessing you
> would want to access the serial port through the RTLinux subsystem to be
> sure of communicating in a timely manner.

A starting point for doing this is:

http://www-public.rz.uni-duesseldorf.de/~jochen/computer/software/rt_com/

> I am interested in the Pic Servo because is looks to be a cost effective

way

> to add closed loop motion control to my mill.

Some observations about the marriage of the EMC to the PIC-Servo system:

1. If I understand correctly, the Pic-Servo boards do the servo control
themselves and you feed them position commands. I have two reservations about
this:

A. You are wasting a lot of the EMC's capabilities.

B. How are multiaxis moves coordinated?

2. If you want closed loop control there are a couple other ways to go that
might be easier (and just as cheap) than using the PIC-Servo boards:

A. If you don't yet have motors, go with steppers and add encoder feedback.
This could be accomplished by interfacing the encoders to the EMC via Tom &
Dan's DRO board. Making this work with the EMC is something that would be
useful in a wide variety of applications.

B. If you want servo motors (or already have a servo motor equipped mill to
retrofit), and don't want to spring for the Servo-To-Go board (understandable
at $888) consider helping pitch in to develop a clone. I'm interested in
doing this myself and I think we've got a head start with the DRO board. We
would need to add a D/A board, but the software modifications would be less
drastic than developing a serial port connected controller. Once it works we
might be able to get Dan & Tom to add the circuitry to their next batch of
boards.

Matt