FPGA C Interface - How to Use NiFpga_AcquireFifoRead and NiFpga_AcquireFifoWrite Methods

[John80]

I am looking at the new methods here for acquiring write/read elements to avoid an extra copy from user-mode to kernel-mode here:

http://zone.ni.com/reference/en-XX/help/372928G-01/capi/functions_fifo_write_acquire/

Are there any examples of how to use these methods?

thanks,

[TheNIDragon]

Hello John80,

Thanks for posting! The FPGA C Interface API installs with examples to help users understand those various functions you linked to. The examples are installed to specific locations and can be located by following this document:

http://zone.ni.com/reference/en-XX/help/372928G-01/capi/examples/

I would recommend the example located in the FIFOs folder named Example.c to investigate further how these functions work. On my system, that is located in the following location (because I have CVI installed):

C:\Users\Public\Documents\National Instruments\CVI\Samples\FPGA Interface C API\FIFOs\Example.c

Just to give you some background information, the FPGA C interface API was originally created for C developers interested in interfacing with bitfiles they created in LabVIEW FPGA. I was wondering if you had any more information as to the application you are working on and what you mean by avoiding an extra copy from user-mode to kernel-mode.

[John80]

I am trying to figure out how low the latency can be for using an FPGA from the CPU to solve problems.  I work for a Financial Firm that deals with lots of problems and I am looking for a way to solve them by using FPGAs.

Also, can you point me to some list of hardware that supports this method? I tried on a Linux machine and I am getting error code -63193 (FeatureNotSupported)

I guess my PXI-7953R is not ready for this!

[Great_Britton]

Hey,

Have you gotten any examples to run with your PXI-7953R? Also, how are you developing the FPGA code itself?

[John80]

No luck with the 7953R, I am assumming that the 7953R does not support this feature because of the error code. Although I do see the corresponding functions in nikal.c

[Great_Britton]

Sometimes that error code can indicate another problem. It might be worth trying the card in a different slot, or trying a different card if you have one around.

[speleato]

Hi John80,

I can confirm that the PXI-7953R doesn't support NiFpga_AcquireFifoRead and NiFpga_AcquireFifoWrite. If you are interested in PXI class hardware that does support it, you should look at the PXIe-796xR, PXIe-797xR, and PXIe-782xR families of products.

One question for you, how much data are you planning on moving accross the FIFO?

I thought there was a document somewhere the has a list of supported devices for these methods, but I can't seem to find it right now. I'll reply back if I can dig it up.

Sebastian