Pre-puchase question for cRIO

[maxoverclock]

hello all,

our engineering lab is getting ready to purchase a cRio system for control of our robot system.....i have a question from those with some experience with the cRIO system.  i unfortunately do not have to many details on our actual usage since it is for a project that is just starting......we have two choices for our puchase.....both have will have these modules:

9411 encoder input for high speed multiturn encoder

9401 digital input/output for PWM motor control

9215 for sensor inputs

9263 for another project....

my choice is

get a 9002 64mb/32mb real-time controller with a 1M FPGA

or

a 9004 512mb/64mb with a 3M FPGA

the second system is $500 more with is more money than is readily available but it seems that it is such a better deal for a more powerful system that it might be worth it to spend the extra money.

for a digital input-PWM output and 2-4 channels of analogue input PID control sytem with some digital filtering are the extra resources worth the extra money?

thanks, any insight will be most helpful. 

brian

[preston_johnson]

I think the price difference is more than $500.  You might want to double check. 

For simple PWM and Analog Inputs, the 1M gate FPGA should suffice.  You would be surprised with the amount of functionality you can get into the 1M gate FPGA.  the 3M gate has some advantages, twice the DMA RAM (for high speed data transfer) and of course more room to grow your FPGA application. 

The RT controller with 64MB main ram and 512MB of cFlash is also a nice addition.  You can perform more array operations and store more data in memory with this controller.  Probably the more challenging question is what is the RT controller going to do.  Is there a computer nearby that will be always connected?  You might also consider the StarGen controller: http://sine.ni.com/nips/cds/view/p/lang/en/nid/202431  The Stargen controller makes a high speed link between your FPGA backplane and the host computer.  This may be a nice trade-off if a computer is near the cRIO system at deployment. 

Just some ideas.

[maxoverclock]

the price differential is $528........(for academic).....

it is my understanding that it is best to keep as much as possible in the FPGA since it is the fastest.  are there some function relating to standard PID control/fitering/Data acquisition that cannot be run on the FPGA or am i just limited to the # of gates i have.   Will i be able to capture data (at a non-real rate) right from the FPGA and send it to my laptop without the additional Stargen controller?

thanks

brian

[preston_johnson]

All the core functions you need are available from our LabVIEW FPGA tools, and the Digital Filter Design Tools.  It is really a gate issue.  I have a very complex digital filter, pwm, PID application that fits into a 1M gate backplane. I use a 3M gate backplane for the 180k of memory, vs the 90k with the 1M gate backplane.

To connect the backplane, you need either a RT controller (9002/9004) or the Stargen controller.  They both are not usable at the same time with the same FPGA backplane.  So the stargen controller makes the Laptop the controller. 

If you want a PCI interface, to the computer (as compared to Stargen or ethernet of the 9002/9004 controller) you can use a FPGA R series board in your computer, and use cRIO expansion chassis to get the cRIO I/O.  The FPGA backplane then is inside your computer. 

I hope this is not confusing. 

[maxoverclock]

no not confusion......so it looks like the less expensive system will work for me if you are running code like that on the 1M system....thanks for the information....would it be possible after i get the system to look at the code you are describing?

thank you

brian