Using an Ethernet RIO chassis directly with a PXIe controller

[toddy]

I'm looking at getting another PXIe system to perform a similar function to some systems we already have. Currently we use a PXIe controller with an expresscard slot connected to a NI 9157 MXI-Rio expansion chassis. The MXI-Rio chassis however are very expensive, and they're now marked as 'mature' in their lifetime, so I'm looking at alternatives (The fact that you can't get expresscard slots on the newer PXIe controllers also adds further expense to the MXI-Rio route, and takes up another slot in the PXIe chassis).

I don't want to get an EtherCAT-RIO expansion chassis, as it involves using the scan engine which I think is very resource hungry and less flexible compared with doing things in FPGA with FIFOs.

So then I consider the Ethernet-RIO expansion chassis such as the NI-9149. Now the way I'd like to run this is to connect the 9149 to a spare port on the PXIe controller directly, so they are on their own private network. I've found 2 articles which suggest this is not really the correct way to use these chassis;

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA03q000000YGx7CAG&l=en-GB

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA03q000000x4LaCAI&l=en-GB

Both of these articles express this;

Connect the expansion chassis to a Secondary Ethernet port of a cRIO. This way only the cRIO itself will be able to connect to the Expansion Chassis. This setup is not the intended use case for Ethernet RIO expansion chassis.

So my questions are

Does anybody else use an Ethernet-RIO chassis in this way?

Is it likely to be problematic?

Would connecting via a switch (even if nothing else was on that network) be better?

Would there be a problem with using more than 1 Ethernet-RIO chassis in this kind of way (on a private ethernet connection)?

Thanks,

Andrew

[marina_0]

Hi Andrew,​

According to this KB: Setup Guide for Ethernet RIO Expansion Chassis - National Instruments (ni.com) the NI 9146, NI 9147, NI 9148, and NI 9149 Ethernet RIO expansion chassis allow you to easily add NI C Series mixed-signal-conditioned I/O to any Ethernet network. The chassis can be added as a stand-alone target to a Windows-based system or used as remote expansion I/O for systems based on NI LabVIEW Real-Time such as NI CompactRIO or NI PXI—just connect over Ethernet and instantly obtain access to C Series I/O in your LabVIEW host program. So you can definitely connect a 9149 to a secondary port of a PXI controller. Please note also that you might need to use a crossover cable: Using a Crossover Cable to Connect to a LabVIEW Real-Time Target - National Instruments (ni.com). Although most modern switches handle that functionality, so if you connect 2 similar devices to each other through a switch, not any crossover cable is needed. And connecting 2 9149 devices through a switch sounds pretty ok, and I think won't cause any issue. It is definitely not a problem using a private Ethernet network at all. But why don't you want to use MXI to expand your configuration though a PXI chassis, that is more reliable way for an expansion. 

Best,

Rina

[toddy]

Hi Rina,

Thank you for your reply.

I guess there are 2 reasons why I don't necessarily want to go the MXI route:

1. The MXI-RIO products are 'mature', and there have been no new MXI-RIO products for many years as far as I can see. I fear this might be a dead-end in the NI product roadmap
2. The cost of the MXI setup is much more than (the MXI-RIO costs 2.8 x the ethernet-RIO on a cost per c-series slot basis) the equivalent Ethernet setup

If the Ethernet-RIO system can do what I need then I think it may be a safer long-term bet, and cheaper in the short-term.

Cheers,

Andrew