Trying to get I and Q value from USRP-2955

[Idansh08]

Hi all,

I'm new to labview, and i'm trying to get I and Q values on the FPGA, so i can do some math (fft for example) on he FPGA (not host).

I've seen some examples about it, and got to a conclusion that i need an I/O node of RF0/RX1/I(Q), but i couldn't find it.

I'm using labview 2016 and own USRP-2955.

Thanks!

[wiebe@CARYA]

This is a wild guess (don't currently have USRP drivers installed):

could it be that the read VI is polymorphic? If you right click and select Visible Items, can you check "Polymorphic VI Selector"?

Guess 2:

The data might be interleaved. Use Decimate Array to split it into I and Q (I,Q,I,Q,I,Q,... -> I,I,I,... and Q,Q,Q,...).

[Idansh08]

1. Do you mean VI of the FFT example i found? Or the new project?

2. Do you have any idea how can I check if this is true?

[wiebe@CARYA]

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@Idansh08 wrote:

1. Do you mean VI of the FFT example i found? Or the new project?

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The read VI. Remember, it's a guess.

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Idansh08 wrote:

2. Do you have any idea how can I check if this is true?

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Look at the data from the read VI. If the data is interleaved it looks like two signals mixed together in one signal.

[wiebe@CARYA]

A code snippet of what you have so far might be useful.

[Idansh08]

Attached two files, "Streaming Xcvr(FPGA).vi" is an example I found (someone uploaded it with a question).

"Streaming 2945 2955" is just a simple LabView example for NI-USRP 2955 with the thing you said about the I and Q (on the FPGA vi).

[wiebe@CARYA]

Well, half the code is broken since I don't have FPGA or USRP installed.

But the RF 0/Rx/I and RF 0/Rx/Q (just left from the to I16 to IQ vi's) seem to return the I and Q signals.

[Idansh08]

That's probably correct, but when I open my own project, I don't have any  RF 0/Rx/I or  RF 0/Rx/Q, I have only as shown in the picture

[UMASO]

Hello, I ran into the same question, using USRP-2945.  I know its been 5 years since your last post above, and hope you solved your situation at that time.  

As I ran into the same question as yours, I checked hardware architecture of USRP-2945 and found an article blow.   

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019Y9TSAU&l=ja-JP

Looks like USRP-2945/2955 has heterodyne architecture which is different from other USRP-RIO devices.  What we have from IO node "RF 0/Rx/Rx1" for 2945/2955 is IF signal, while I/Q is directly provided from IO node for other USRP RIO devices.  To further downconvert the IF to get IQ, DDCs are applied right after the IO node of IF signal.  So, IQ for 2945/2955 are not provided from IO node only, but from DDC output.  

Best regards,