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Best way to get digitizer p2p data to fxp in FPGA

Hi everybody,

 

Currently I am working with a setup that contains a NI5122 digitizer and an 7966R FPGA module.

The p2p stream between the Digitizer and the FPGA is working but I want to do some digital signal processing and controlling based on the scope data.

I am a bit confused about the data format the scope streams via the P2P channel.

 

As most of the DSP stuff is going on in fixed-point format I would like to know what is the easiest way to get  a measured analog value like 1.7V to a fxp representation that can be used in the FPGA?

 

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Hi!

 

Can you give an example of your data source from where you want to convert your data to fixed point to?

Do you mean the I/O node of digitizer?

BTW: Attaching an example VI (snippet) is almost always a good thing.

 

Regards,

Christoph

Staff Applications Engineer
National Instruments
Certified LabVIEW Developer (CLD), Certified LabVIEW Embedded Systems Developer (CLED)


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Hi,

thanks for the reply.

So what I actually try to do is to sample analog data via my NI-5122 PXI card and stream it via p2p to the FPGA card in the same PXI reg. As I am quite new to DSP and LabView I´m a bit confused about processing the streamed data.

 

In my testsetup I use a 1.5V reference on my 5122 Scope input and if I just read the I16 P2P data from the FPGA and do the conversion to voltage (V=I16*gain + offset) on my host computer I get exactly the 1.5V. However for my final application I want to do the conversion from Raw I16 to voltage on FPGA side as I would like to process the data there using high throughput math functions. I tried to do it in a naive way but I end up with different results(i see an offset with a somehow nonlinear behaviour) so i must be doing something wrong 😄 .

 

Is there an easy way to get from the I16 Value from the scope to a fixed point representation of the voltage? E.g. Input 1.5V = 19000 (I16) = 1.4999 (fxp)

 

 

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Ok i think i found the problem....

I didn´t paid enough attention to the fxp resolution as the gain of the scope is very low i need more bits to represent it.

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