cRIO/FPGA/RT basic concepts

[CoastalLabVIEWER]

I have no experience with any of these and I'm trying to figure out where to wade into the pond.  I'm doing testing on electro-hydraulic actuators and I am needing to control them with dedicated, deterministic hardware.  The test executive is running on a Windows system.  All sequencing and control of the system needs to happen from this machine.  The system needs to be programmable to have up to 3 AOs acting on feedback from 6 AIs in the 500Hz-5KHz range.  We currently have a PXI rack connected to the main system via MXI.  At first I thought something like a PXI-7852 was what I need but now I'm not so sure.  Where does the cRIO come into play in this decision?

Can the rest of the LabVIEW system interact directly with the code running on the FPGA target as if it was just another VI or does this communication have to be done over Ethernet or some other means?

[tannerite]

Hi SmokeMonster,

Since you already have a PXI chassis, the PXI-7852 would be a great option if you have available slots in your chassis. The PXI-7852 has 8 analog inputs and outputs, which would fit your needs very well. As for the feedback situation, the FPGA on an R-Series board would be a great fit if you want a responsive control loop.

As for communicating with the FPGA, you would need to create a host VI with a reference to the FPGA. From there, you can transfer data through controls and indicators, or for very quick data transfers, you can use a DMA FIFO to pass data to and from the FPGA from the host VI. The host VI is just like any other type of VI. The only difference is that you will need to add a reference to the FPGA to be able to control it. 

The Compact RIO is for distributed controls applications. You can communicate with the Compact RIO via Ethernet communication. The Compact RIO has it's own real-time operating system that then communicates with the FPGA. It does not require any computer interface; therefore, it can run headlessly in the field and log data using the real-time operating system.

If your system does not need to be distributed, then the PXI-7852 card should work very well. I hope this information helps, and if you have any more questions feel free to ask!