(soft)Real Time Ethernet

[Ale914]

I need to develop a network distributed application for data monitoring and control so i must create the comunication protocol.

I think to implemet my protocol over UDP protocol using standard ETH but i need a fast and deterministic comunication, do you have experience in this application of ethernet?

Bye, Alessandro.

PS sorry for my english

[Khalid]

I need to develop a network distributed application for data monitoring and control so i must create the comunication protocol.

1301[/snapback]

Hi Alessandro,

This is not a direct answer to your question... just want to make you aware of an existing product -- the Datalogging and Supervisory Control (DSC) module for LabVIEW, which has built-in networking functionality for monitoring and control.

Please visit the following page for more info' on the LabVIEW-DSC module:

http://sine.ni.com/apps/we/nioc.vp?cid=10418〈=US

:question: Why re-invent the wheel? You should take into account the development AND maintenance time for the really-proprietary networking protocol. I guess it depends on how big/small of an application you're developing.

Regards,

Khalid Ansari

[didierj]

Alessandro,

UDP (as well as TCP) is a non-deterministic protocol. But, many tests were made to still use TCP/UDP as a deterministic system:

- If you have just 2 partner (with full duplex crossed ethernet cable) then deterministic is no problem, because TX of on computer is connected to RX of the other. You will never see collisions.

- If you have more than 2 partner, build local segments in your ethernet the way that in a segment the traffic never rise over about 5%. Then collisions are so rare that you almost can forget them.

Another tip: If you just collect data,

- either use Khalid's proposal or

- use for the data acquisition stations intelligent systems (such as Fieldpoint/PXI with LV real-time), set on this intelligent system a timestamp for every datapoint and then send it over the ethernet. This way your central station always knows when something occured and it can link the data of the different stations in correct order (even if the data arrives 1-2 seconds later).

Didier