CRIO FPGA Timing Loops - Which do I choose

[Tim_C.]

I have a CRIO 9012

I will be be doing very basic voltage, mv, and thermal couple readings.

Data rate of once per second is to read the input is fine.

Modules being used - 9221, 9215, 9211

Also using a GPIB-RS232 converter via the com1 on teh CRIO,  this is being used to adjust DC load modules in an

Agilent N3300A DC Load Bank.

Test Plan

FPGA gets AIs,  feeds data to CRIO Host VI,  PC Host interacts with CRIO Host VI through Network shared variables.

Logging takes place on  PC  as PC also has a USB Elm compliant OBDII device that is polled to retrieve the trucks RPM.

Basically wondering what is the best timing engine for an app like this.

Thanks

Tim C.

[Ben_S]

Tim,

I'm exactly sure what you mean by "timing engine", but depending on what backplane you have, you can use the scan engine on your cRIO to do your data aqusition from your c-series modules. You can also very easily configure the scan engine to update at a 1HZ rate or use a timed loop that runs once a second with your scan engine variables in it and have your scan engine updating more quickly.

I would also reccomend having seperate loops in your Real-Time code for your different functions. By this I mean have a loop for your scan engine I/O and a seperate loop for your GPIB control.

On your PC Host Code, I would also reccomend having seperate loops for your I/O, Control, and Logging.

[Tim_C.]

The FPGA wizard lets you select

Single Point Continuous Loop

Signle Point Timed I/O Loop

Buffered DMA

Thanks

Tim C.

[Ben_S]

Tim C.

Thanks for reminding me of the FPGA Wizard, I wasn't thinking about that.

You can generate all three timing engines in one VI with the wizard and inspect them to see which you like better. I would reccomend starting with the Single Point Timed as this will allow you to set the loop rate to 1HZ which isn't fast enough to warrant using DMA's.