9870 FIFO I/O Buffer

[william15]

Hey,

I'm working on a project that has multiple serial inputs going into a 9870.  I tried running a loop to constant check the 4 ports to see if there was new data, but that tied up too many resources so I resulted to putting anything device that sent data back to me on a VISA port.

My question is about the FIFO Buffer that the 9870 Has.  Will incoming data from the 4 serials be stored into the buffer and whenever I choose to I can read from it like a VISA port?  This may seem like a simple question, but I want to be sure before I come to my team with this solution.

Thanks

[Hillman]

Hi William,

Maybe this example on the NI site will help regarding your questions.

NI 9870 - Continuous Serial Read - On-Demand Write

 There should also be examples in the LabVIEW NI Example Finder, goto Help>>NI Examples and search '9870'.

I believe the modules have buffer built into the module. But normally with FPGA/Real Time development on the cRIO platform you would implement FIFOs due to the differences in clock speed between the FPGA, Real Time processor and the User interface (if you have one).

Let me know if the examples don't help at all. 

[dskrabacz]

Hi,

I am dealing with the CompactRIO 9074 and I have connected the 9870 up to this chassis. I am using the example virtual instrument that was recommended from James. I was able to input all of my Read_FIFO and Write_FIFO with my specific ports, and have modified the ports. When I run the FPGA program, it initializes to step 7, and then exits with the following error message: "Too many DMA channels have been requested or some requested are conflicting. The current target has 3 DMA channels." Does anyone have a fix for this? Thanks.

-Daniel Skrabacz

[BTreece]

Hi Daniel

It appears that you are already working on this issue on another forum that has already been replied to.  That can be found here:  http://forums.ni.com/t5/LabVIEW/Module-9870-for-reading-4-serial-devices/m-p/1459422.  Good luck with your application!

Brandon Treece

Applications Engineer

National Instruments