On Jan 31, 2010, at 10:06 AM, PICdude wrote:

> - Talk to stepper motor drivers and servos

Except for this, you're well into to "straight PC" category, and there  
ARE external motor controllers you can connect up.  They're  
particularly common and inexpensive for servos (eg http://www.pololu.com/catalog/product/207 
  ) Stepper controllers will be harder to find, I think, and more  
expensive (since it involves power drivers.)

Here's a 4-motor stepper controller: http://www.trossenrobotics.com/phidgetstepper-unipolar-usb-4-motor-stepper-controller.aspx?feed=Froogle

I'll second the recommendation for Arduino; not as the overall  
solution to your request, but as the low-level interface between a PC  
and actual hardware stuff.  This is one of the niches that Arduino  
where arduino has secured a spot.  An Arduino plus OTS motor driver (2  
servos + 2 steppers) would run about $50 and provide for analog sensor  
connections and additional digital outputs (blinking lights) as well!  
OTOH:


> My other major concern is its ability to deliver stepper pulses at
> over 1MHz to each of a few steppers simultaneously at different
> speeds, cause IIRC it runs on a 16Mhz or 20Mhz microcontroller.

I'm pretty sure that that's WAY far out on the bell curve WRT stepper  
drivers.  I don't think there is any way you're going to achieve that  
without dedicated hardware drivers.  (and looking at some of the  
dedicated hardware from Allegro, it seems that 500kHz is a more  
typical max step frequency.)  I'm also pretty sure that not very many  
"high performance" processors can achieve that sort of pulse frequency  
under SW control.  2GHz may sound really fast, but once you start  
trying to do IO off-chip, things slow WAY down...  (the above  
referenced stepper controller apparently maxes out at about 350 half- 
steps/second...)

> I have a not-currently-in-use Mini-ITX mobo here (with PS, RAM, etc),
> and really want to use that, unless someone can talk me out of it, but
> need to find an O.S. for this.  A decent low-cost real-time Linux O.S.
> would be nice, or a regular Linux distro if I use the hardware
> interfaces for the stepper/servos.  But I don't know what the current
> offerings are for programming languages/environments on that -- any
> decent/simple IDEs?

Processing (processing.org) is Java, and has a supposedly beginner- 
friendly IDE (the same one used for Arduino, more or less.)  Realbasic  
(realbasic.com) is also pretty nice (not free, except for eval,  
though.)  Both are multi-OS homed (Windows, Mac, linux.)  I'm not sure  
about other "teaching" IDEs; when I use linux I tend to be using   
"professional mode" toolsets (bash/gcc/make, or maybe eclipse), but I  
don't think anyone has ever claimed that those are "simple."

BillW

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