Daisy Chain 2 NI cFP-1808

[ASTDan]

Hello,

I am trying to find some documententaion that explains how to Daisy Chain 2 NI cFP-1808, which is Network interface modules for the Compact Fieldpoint platform. http://sine.ni.com/nips/cds/view/p/lang/en/nid/202210

I am also trying to find out what are the performance hits when adding 1 or more cFP-1808 to a system.

Also has anybody had experience doing this and what did you observe?

Thanks

Dan

[Dan Press]

I do not think that those units can be daisy-chained. They are Ethernet interfaces, so you can just wire one or more of them to a subnet. That's not technically daisy-chaining. If you use a dedicated subnet, there should be plenty of bandwidth to do data collection across multiple units.

The only performance hit I've seen is that the initial communication with the unit tends to take a few seconds. Once communications are established, the data flows nicely. cFP is not a particularly fast data acquisition platform. It is great for things like air temperature that do not change too rapidly. If you need to sample fast, consider the Compact RIO.

[ASTDan]

QUOTE(Dan Press @ Sep 26 2007, 03:10 PM)

I do not think that those units can be daisy-chained. They are Ethernet interfaces, so you can just wire one or more of them to a subnet. That's not technically daisy-chaining. If you use a dedicated subnet, there should be plenty of bandwidth to do data collection across multiple units.

The only performance hit I've seen is that the initial communication with the unit tends to take a few seconds. Once communications are established, the data flows nicely. cFP is not a particularly fast data acquisition platform. It is great for things like air temperature that do not change too rapidly. If you need to sample fast, consider the Compact RIO.

The AI module I am looking at can sample up to 10kHz which is fast enough for my application. So bacically I need a router or a hub to monitor 2 interfaces? Would it be a good idea to acquire data from each backplane in 2 differnt loops? I have a lot of temperatures to monitor. Should I put my low speed stuff on 1 interface and the relativly fast stuff on the 2nd interface and montor them using seperate loops?

Thanks

Dan

[Yair]

I haven't looked into this for the 180x, but you should note that your actual acquisition rate will probably be determined by the AI module rate + the time it takes the cFP to poll all its modules + the communication time, which means I doubt you'll be able to get up to 10khz.

You shouldn't have a problem with having separate loops, since you just have a different IP address for each device and can talk to them like that. It really as simple as buying a simple router or hub and connecting both modules and your computer to it so that they are in the same network.

However, if you want high speed, relatively cheap DAQ and you don't NEED the network connectivity, I think compactDAQ might be what you want, but I don't have any experience with it.