Deterministic Ethernet over long distance

[Ben]

I'm looking for hints, techniques, and hardware suggestions for setting up a network of cRIO's all controlled by a single PC.

The cRIO's will be scatered throughout a mine with the farthest run being just short of 5000 feet from the control room.

We are concidering running fiber but I am concerned about "off-the-shelf" network hardware being able to propogate the deterministic protocol.

So....

Has anyone done something similar?

What kind of ethernet to fiber (and back) converters did you use?

Any other words of wisdom will be appreciated greatly!

Ben

[unclebump]

Hi Ben,

Are you using special hardware or protocol?? Due to the collisions, I was under the impression a network is non-deterministic.

http://web1.automationdirect.com/adc/Overview/Catalog/Communication_Products/Ethernet

Message Edited by unclebump on 09-08-2006 10:38 AM

[Ben]

Hi Uncle,

You are correct for normal E-net.

NI now has deterministic ethernet that use the physical layer but use ther own proprietary protocol that is deterministic.

Your link says "The E-SW05U supports all standard IEEE 802.3 Ethernet protocols, "

THe protocol replace the OSI stack with their API.

It uses a master slave relationship with every node having a dedicated time slot, so no collisions.

Since the protocol is non-standard, I am concerned with the E-net to fiber adapters not propogating the Determinisitic Ethernet protocol packets.

Ben

When watching a video where a hero is out-running an explosion in a tunel. some may wonder just how fast they have to run. This application will be meassuring that.

Message Edited by Ben on 09-08-2006 10:41 AM

[unclebump]

Have you seen this app note??

http://zone.ni.com/devzone/conceptd.nsf/webmain/EDF87E5F1D7BAA898625706E007A67C7?opendocument&node=3...

[Ben]

Yes that the critter!

I need to run it over fiber and there is the rub.

Ben

[unclebump]

I ran into a similar situation trying to get modbus talking over our broadband modem network to a Vax almost 16 years ago. Modbus had a nine bit datastream(8data bits plus parity)  and the modem only supported 7 data bits plus parity. A newer model of modem worked fine.

[Justin D]

Ben,

The time triggered shared variables that are discussed in that app note only work in PXI RT and Desktop ETS controllers (not in cRIO or Fieldpoint).  With that being said you would most likely not be able to use a fiber converter with this type of network because our protocol is proprietary so it may not work with the handshaking/traffic handling etc. that a standard converter would probably use for standard ethernet.

I hope this helps,
Justin D.
Applications Engineer
National Instruments

[Ben]

Hi Justin,

You wrote

"The time triggered shared variables that are discussed in that app note only work in PXI RT and Desktop ETS controllers (not in cRIO or Fieldpoint).  "

Well it looks like I am going back to "Plan A".

Ben

PS: You are certain the above is coorect?

Message Edited by Ben on 09-11-2006 02:01 PM

[unclebump]

Hi Ben,

I know you can get fiber converters for a modbus plus network.

[Ben]

Thanks for the suggestion Uncle!

Now does the cRIO support Modbus and what is the top transfer rate available for Modbus ( If you do not know off-hand, please do not research those answer on my behalf. I will address those question in another thread)?

Ben