RE: FPGA for PCI based servo control board

["Craig Edwards" <cedwards-at-ceinetworks.com>]

Thanks Eric... This looks like just what is needed.  Now we just need
someone to download / install / run to determine what the round trip latency
might be on a typical 1GHz system.  Ideally it would be nice to know what
the latency for both upstream and downstream segments look like.

Craig Edwards

BTW, I've used those mini-ITX boards, it's a great format.... And no you
won't beat the price....:)

-----Original Message-----
From: emc-at-nist.gov [emc-at-nist.gov] On Behalf Of ERIC KELLER
Sent: Friday, April 04, 2003 9:20 AM
To: Multiple recipients of list
Subject: Re: FPGA for PCI based servo control board





Using a standard nic for real time communication has been done a number of
times now.  Look at RTnet: http://www.rts.uni-hannover.de/rtnet/

I don't know where you are going to get a cheaper embedded computer than a
VIA elan board

http://www.newegg.com/app/Showimage.asp?image=13-180-025-04.JPG/13-180-025-0
3.JPG/13-180-025-01.JPG/13-180-025-02.JPG

Eric

 
> >  If the Linux
> >drivers are indeed not accessible to real-time tasks,
> >then any ethernet solution will require writing a
> >real-time compatible NIC driver for every brand of
> >NIC.  On the other hand, if real-time tasks can
> >use the existing Linux NIC drivers with a clean
> >raw packet interface, ethernet looks very good!
> >
> No way.  It might be possible to extract a common section of the 
> protocol stack, and use that as the basis for the RT code.  But, it 
> would almost always require hand massaging, I'm afraid.  Once you go 
> outside the RT code for anything, you are, BY DEFINITION, no longer 
> real-time.  That code could lose control due to a higher priority 
> task, and the message would not get there in time.
> 
> Jon
> 
> 
> 
>