Re: [Emc-developers] Hardware, wires and no place to connect

[Neil W. <ko...@fi...>]

Hello,
I guess I should have been more specific when I was discussing the 
topology about connecting to a WAN, or even a non-related internal 
network. I had intended to imply that 
the WAN/LAN and the module network would be separate, one network card for 
each. However, with a proper VLAN switch, I feel that it MAY be possible 
to combine them, but I am not going to spend any time on that. ;)
I have looked into a few realtime Ethernet papers and implementations such 
as Rtnet, Rether, and MicroNet, and it appears that Rtnet has most of 
what is needed for the host side (if not work just fine as-is). However 
for the I/O module side, the Ethernet stacks by Atmel and the like are 
nearly useless to me because they are targeted 
for much more complex (expensive) microcontrollers. (The compiled 
Atmel stack is nearly 3 times the size of the total flash of the 
microcontroller I am considering using.) Call me cheap, you'd be 
right, but why throw all of the complexity and money at it when it is 
likely that the cheaper, simpler approach is likely to provide the best 
answer.

-Neil Whelchel-
C-Cubed
760 366-0126
- I don't do Window$, that's what the janitor is for -

Can anything be sadder than work left unfinished? Yes, work never begun.

On Sat, 29 Mar 2008, Jon Elson wrote:

> Neil Whelchel wrote:
>> Hello,
>> I have joined this list because I an working on a project to convert my
>> old CNC mill and manual lathe to EMC and I saw that there are what seem to
>> be limited methods of interfacing EMC to the outside world, and I think I
>> might be able to help in this area, among others. Sure there is the
>> parallel port, and a hand full of (supported) ISA and PIC boards, but none
>> of them seem to provide an optimal interface, and others are simply not in
>> the right price range to make a project feasible. I have been tossing
>> around the idea for a few months now of creating some very cheap (open
>> source) microcontroller based I/O modules that communicate using Ethernet
>> at the layer 3 level (Network Layer).
> There is a real-time Ethernet driver already in existance, but
> there are a number of restrictions on how it works.  Also, these
> restrictions means it won't work with off the shelf ethernet
> micros and their off the shelf ethernet stacks, such as Atmel
> and NXP make.  At least, that was my understanding.  Whether the
> micro's library can be adjusted to make it work with the RT-net,
> I don't know.  The RT-net requires total isolation of the RT
> part from the WAN with a router that can handle the RT-net
> flavor, so that pretty much has to be another computer with two
> ethernet cards/ports.
>
> I wanted to provide an ethernet interface to my boards, which
> are parallel port based right now.  But, this was just over my
> head and beyond the time I had available.
>
> Jon
>
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