Intro and step/direction question

[The President]

Hi everyone. I am a mechanical engineer working in the area of aluminium casting machines. This has nothing to do with my interest in hobby CNC - I just thought I'd mention it.
My first CNC project was a small x-y table that I mounted under a milling head to do some engraving in brass - see attached photo. I made the controller myself out of a PIC16F84 chip, some EEPROM and a MOTORMIND dual motor driver from Solutions cubed. For what it was, it worked ok.
That was three years ago and I have since not done anything else, except admire other people's work.
I have recently hit the drawing board with a very original concept. I plan to control it using an industrial stand-alone controller that can output a plus/minus 10 volt dc signal to feed into a brush or brushless driver. It can also output step/direction signals. I plan to use the latter to drive some steppers. However, I am also aware that some brush dc motor drivers can also operate off step/direction signals (eg. Gecko drive). What I want to know is, would the output be smooth, eg for linear or circular interpolation?

[DennisCNC]

Are you asking if your controller will have a smooth output of step/dir or are you asking in general if a step/dir signal will make a nice circle or diagonal line?
If in general I can say that it will smoother than you can imagine. If you are asking about your controller, then I don't know

[pminmo]

Step/dir is only limited by resolution of the conversion technique. In theory you could have infinitesimally small step sizes. Practically it becomes the motor, electronics and rotart to linear conversion.

[The President]

Servo drivers that accept step/dir signals are commonplace. If their output was granular or jerky, I dont think they would be out there, so I probably asked a dumb question.
The source of my doubt came from the fact that when you provide the driver with a rapid succession of step pulses, are you confusing the PID system?

[Larken]

However, I am also aware that some brush dc motor drivers can also operate off step/direction signals (eg. Gecko drive). What I want to know is, would the output be smooth, eg for linear or circular interpolation?

The other question is, is the +-10V output accurate, because It would have to be closed loop.
I'm sure the s/d output is ramped and interpolated to get the smoothness and accuracy.
Depending on how the circular path is created, the circle can be accurate or sloppy. Many controllers are velocity driven and position is corrected at a constant loop time, so the faster you go the more the error gets.
A software interpolated controller calculates each x,y step with perfect accuracy, but its velocity control may not be as good.

[The President]

Thanks Larken, that shed more light on it.