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Ethernet communication with NI9149

Hi everyone,

 

I would like to create a rugged system by interconnecting several units by means of Ethernet for a measurement and control application. My question is if I can connect NI9149 chassis over the ethernet directly for control and communication with the modules attached to the chasis and application or is required an additional ethernet controller for each unit. The application is created in Measurement Studio. The system diagram is presented in attached file. Thanks.

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Dorin1984, 

 

I believe the first part of the following document may answer your question: 

 

Connect an Ethernet RIO Expansion Chassis to a Secondary Ethernet Port on a Real-Time Controller - https://knowledge.ni.com/KnowledgeArticleDetails?id=kA03q000000x4LaCAI&l=en-US

 

"The Ethernet RIO expansion chassis is intended to be connected to a switch, router, or existing Ethernet network; however, you can connect it to the secondary port of a real-time controller." 

 

The setup guide may also be helpful. 

 

Setup Guide for Ethernet RIO Expansion Chassis: https://knowledge.ni.com/KnowledgeArticleDetails?id=kA03q000000YGx7CAG&l=en-US

 

Will M.
Applications Engineer
National Instruments
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The 9149 gives you direct access to I/O using a technology called shared variables, which should be accessible from measurement studio. Shared variables are a peer-to-peer protocol meaning you just need to connect the 9149 to your network and you should be able to get data.

 

However, shared variables are lossy and have a maximum rate -- I've seen something on the order of about 50-100 Hz update rates mentioned in various locations, although performance will be application and network specific. If you need faster performance you will have to use a FIFO (allowing you to stream data) and you will have to program the FPGA using the LabVIEW FPGA module. I believe you should be able to interface with the FPGA but it will require using the LabVIEW FPGA C interface and you must be able to call the dll from measurement studio. There may be an easier mechanism I am unaware of.

 

You may also consider ethercat for your application which does require a separate real-time host but is also a faster protocol. A good comparison of options is here: https://www.ni.com/en/shop/compactrio/expansion-i-o-for-labview-rio-systems--an-in-depth-comparison....

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