Re: Firewire

[Phil Wilshire <philwil-at-earthlink.net>]

Hi All,
I am most interested in any use of Firewire.
I too have headr that it can be made deterministic and that the chips
are cheap.

It is already well supported under Linux.

I guess what we need is a simple firewire based equivalent of the
parallel port to play with.

Any comments ??

regards
  Phil Wilshire

Ray Henry wrote:
> 
> Hi
> 
> I've been in conversation with Bert Eding about some graphical stuff that
> he is using with his EMC.  During that conversation he mentioned some
> things about firewire that I thought the hardware types would find
> fascinating.
> 
> Just a bit of background to re-introduce Bert to the rest of the list.
> Bert is a delightful fellow and wonderful cook.  He lives in Eindhoven,
> the Netherlands.  He works for Nyquist, a specialized motion control
> company.  The first page of Nyquist's web presence (www.nyquist.nl) says,
> 
> " Nyquist Industrial Control develops and sells Motion Control systems to
> OEM customers who create semiconductor production equipment, special
> robotics and factory automation equipment. Our systems allow these
> machines to make lightning fast movements that are accurate down to the
> nanometer."
> 
> Bert's setup is not what a casual user might call a typical EMC.  He has
> fitted a desktop mill with servos and drives them using big dollar
> Nyquist servo drive boards.  Bert uses Firewire to communicate between
> his PC and his drive amps.  When I saw his mill do it's thing, he had
> modified the EMC to run under MS-NT.  He is now using MS-XP.
> 
> This led me immediatly to two questions.
> 
> 1 - Real-Time and XP?
> 2 - Firewire hardware?
> 
> Being an "open source" person,  I'm not really interested in bringing a
> MS version of the EMC to the marketplace but there is lots to learn from
> someone who has worked with them.  It turns out that both questions are
> answered by the use of Nyquist equipment.
> 
> > It is currently depending on the Nyquist motion controller.
> > As You know windows is not real-time, or You have to buy
> > the rather expensive VentureCom RTX.
> 
> > But the system what I have is different, the PID software runs at
> > the other side of the cable, not in the PC. The PC sends cubic splines
> > to the system.
> 
> I believe that the way that Bert gets around the latency of the MS-XP is
> by having the Nyquist system buffer the splines and do the hard real time
> servo loop off the PC in hardware.  This is very similar to the
> approaches that have been taken with USB by projects like the Gecko 2002.
> I believe that is is also very similar to the stuff that Steve Stallings
> showed at NAMES a couple years back.  Enough of that.
> 
> I found Bert's comments about firewire to be really interesting.
> Detractors can say, "yea but this guy works for a company that uses
> firewire.  They know how to do it and have the investment already made!"
> Bert says;
> 
> > Another problem, I have no hardware, I would like to have hardware
> > based on FireWire. As You know, Nyquist is using the firewire for
> > realtime motion control. It is perfectly realtime, the timer tick on
> > firewire can be set in multiple of 0.125 us, perfect for servo systems.
> 
> Now that really got me to thinking.  Matt and several others have
> mentioned 1 ms as the native or best-you-can-expect speed of USB which
> makes for a fairly unreliable communication channel for the kinds of info
> that we need to pass.  This 0.125 us seems like it would really open up
> the connection and allow us to do some interesting things.
> 
> > In the Nyquist system, you can connect upto 63 nodes to the firewire.
> > Each node has a DSP and controls 4 axes.  All nodes run up to nano
> > seconds synchrounous with ussage of the 0.125 us timer tick of the
> > firewire.
> <s>
> > Maybe this is also interresting:
> > 1) Firewire boards cost only $25 at the moment.
> > 2) If the PID loop of the software also performs the velocity
> >     loop, and sent torque outputs instead of velocity you can
> >     save a lot on hardware too.
> >     - a 12 bits DAC is more than enough to control torque.
> >     - the servo amplifier can be a lot cheaper,
> >       because the velocity loop is now in software.
> 
> Bert has recently subscribed to the list again.  Where my post contains
> errors, he can correct them and fill in details for you.
> 
> Ray

-- 
SDCS -- System Design & Consulting Services LLC, http://www.sysdcs.com
** Embedded Linux Training **  email me for details  
630 Springhouse Sq., Leesburg VA 20175 t: 703 669 9766 f: 703 669 9768