783xR Analog I/O

[chrissyPu]

Hi,

i just got a NI 7830R for my diploma thesis. My task is to simultaneously

- give out a specific waveform at a given frequency

- give out some analog voltages as a set point for control applications (these can be considered changing very slow compared to the waveform)

- record 4 independent channels of analog input at a rate of 10 kHz

I'm only using the FPGA on the NI 7830R and a non-Real-Time LabView on my WindowsXP-machine. For configuring analog outputs I found enough material in the knowledgebase and the manuals, but I still have some questions about sampling and the analog inputs - I hope I can find some help here... 😉

1. (this is some kind of easy but I just want to be sure): Is it right, that I cannot access analog input or output channels of the 7830R without configuring the FPGA (for example with MAX and the ExpressVI for analog I/O). From the block diagram I assume that I have to configure the FPGA to supply the analog data for access by a Host VI.

2. How do I control sampling rates for the analog channels? The Help-File says that the 7830R doesn't support properties for the analog channels. Can I assume, that the sampling rates given in the documentation (200 kSa for input, 1MSa for output) are used all the time? That would mean an actual sampling of the inputs at 200 kHz and a check for a changing value for the outputs at 1 MHz.

3. I need to sample the 4 analog inputs with a sampling rate of 10 kHz. I could wire an analog I/O-Node in the FPGA to an indicator and read this indicator in my Host-VI with an Read/Write-Control to write it into an array for example. This is quite simple, but I doubt that I can ensure a Sampling rate of 10 kHz with that. Do I have to use a FIFO on the FPGA and read the FIFO with my Host-VI? For my sampling Rate and the execution time of LabView (1 ms) this would mean a size 10 FIFO.

Thanks a lot for help!

Christian

[Wolfgang_Z.]

Hello Christian,

1. There is no test panel in MAX for FPGA boards. But you can load an example for Analog Input from LabVIEW Example Finder to test the board. There is no Express VI for Analog I/O but there is a Wizard to simple generates code for I/O. Right mouse click on FPGA Target in Project Explorer >> Start FPGA Wizard (you need LabVIEW FPGA 8.5 for this).

2. You can control the sampling rates with Loop Timer, Timed Loop or Interrupts.
For sample rates higher than 1000 Hz you should not use Interrupts.
You should use polling or DMA FIFO.

There are some Examples in Example Finder like "Analog Input (FPGA)" or "DMA Buffered Acquisition.

Further read this knowledge base.

Using DMA FIFO to Develop High-Speed Data Acquistion Applications for Reconfigurable I/O Devices
http://zone.ni.com/devzone/cda/tut/p/id/4534


3. Please check example "Analog Input (FPGA)" and "DMA Buffered Acquisition or configure your AI acquisition with the FPGA Wizard.


Please have a look at LabVIEW FPGA Module Training.
http://zone.ni.com/devzone/cda/tut/p/id/3555
There are a lot of information and examples about FPGA programming.


Best regards,
WolfgangZ

[chrissyPu]

Hi Wolfgang,

thanks for your help...

Christian