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ADI Oscilloscope vs GNU Radio and type conversion

Question asked by marcinsztajn on Jul 14, 2016
Latest reply on Jul 20, 2016 by marcinsztajn


I have a problem with GNU Radio Live SDR running remotely on my PC from USB. I am using ZYNQ ZC706 + FMMCOMS3. The problem concerns ADI Oscilloscope and FMCOMMS3 Sink/Source block. I am wondering which application has higher priority, I mean that if I set a LO frequency in my FMCOMMS block in GNU Radio and in the same time I have ADI Oscilloscope running on the PC or on the ZYNQ and LO frequency or sampling rate is different in each programs, which value has higher priority? Value from ADI Oscilloscope or from GNU Radio? Also when I generate One Tone from ADI Oscilloscope I can see him on Spectrum Analyzer but when I close ADI Oscilloscope this tone is still generating from my hardware, I do not know why. Also I have a problem with the Digital Loopback, when I enable it, I see a plot with noise and sometimes i can see nothing. I am wondering what is thedifference between digital and RF loopback.

Also I want to ask about a type conversion in this example:


On this example QT GUI Sink shows nothing. But on this system:


I can see beautiful OFDM spectrum. So problem is with type conversion from complex to float and then from float to short. I am asking about this beacause I have to use this conversion with my FMCOMMS block. When I want to transmit data using OFDM the type conversion lost my data. Somebody know why it happens? Maybe exists any solution how to connect FMCOMMS block in other way.

I will be gratefull for any answer.