Re: FPGA for PCI based servo control board

[John Sheahan <jrsheahan-at-optushome.com.au>]

On Thu, Apr 03, 2003 at 11:58:51AM -0500, jmkasunich-at-ra.rockwell.com wrote:

trimming for others sanity..

> 
> The I/O board is the one that I want to keep really
> simple.  Everybody has different I/O needs.  I'd like
> to keep the design of the I/O board completely open
> and modular.  Ideally, people could cut and paste

agree completely.  with a claen interface. ouch - a new 
strand atarts.

> 
> Give ten engineers a problem and you will get ten
> opinions on how to solve it.  After a lot of talking
> the opinions may begin to converge, but there will
> still be differences.

grin :)

> The solvable problem is how to connect the FPGA
> to the ethernet cable.  What does it cost to add
> ethernet to an embedded project?  

starts with adding a socket, a transformer and a 
cheap part like the 8019.

Then the 64 dollar question, Are you running IP?

if so - you need  the micro and a protocol stack.

if not, the fpga can suck fixed formatted packets 
straight out. 

This impacts on your RT-linux  concern  too,

firing a packet into a dedicated NIC with no collision 
concerns is not hard. (and can be realtime) unlike IP.

That is  a much simpler task than offloading 
the hard realtime , which I do not want to _require_, but 
should be possible, and maybe is where the big gains are,

I acompletely agree with the reinvent-the-wheel concerns.
Unless this is an improvement - why do it.
john