custom cRIO module with independent power supply

[BIRA_PXI]

I have a question regarding the custom cRIO module development. Is it Ok to provide power from the front of the cRIO module like 24V DC to use for the circuit. This power will be totally isolated from the power coming in from the backplane. Will I be violating any cRIO design guidelines if I do this ? The Power from the backplane is not enough for my case.

Thanks, 

bira_pxi

[J.Harv]

bira--

     You should be fine to build in your own external power.  NI has a couple modules that require external power, NI 9265 comes to mind right away.  You'll just need to make sure that this power stays within your circuitry and  doesn't make it to the other components in the system (EEPROM, 15 pin DSUB to the backplane, etc.) I'm not sure how much power you need, isolation could be a consideration. 

     Furthermore, just be sure that you are still adhering to the interface signal voltage levels at the DSUB for communication to the backplane. 

     Using external power will also reduce what you're drawing from the backplane (if anything) and should really lower the in-rush current the module draws, which is a common issue when developing modules.

     Just to be sure I'm speaking to some of NIs module developers to see if there are any other concerns that I can make you aware about, I'll let you know if I find something.

Regards,

John

CompactRIO Product Support Engineer

[BIRA_PXI]

Hello John,

Thanks for the reply. For the labView driver, for this module,can the SPI library be used or do I have to make my own SPI protocol VI.

The SPI library that I am referring to can be found at

http://zone.ni.com/devzone/cda/epd/p/id/6163

Also have you come across any example driver Vi's for reading data over the SPI bus from the custom modules ? 

Thanks, 

birapxi

[J.Harv]

birapxi--

      Unfortunately, those examples are designed to run on LabVIEW for Windows and have a number of unsupported typedefs, clusters, and data types...so they will not directly compile in FPGA.  Theoretically, you could edit them or use them as a reference, you'd probably want to customize and make your own VIs anyway.Editing them to work on FPGA would definitely take longer than writing your own.

      As for examples, the only examples are the 3 that come with the kit.  I'd take a look at those again and review the manual.  If you have specific questions, let us know.

Regards,

John