Re: [USRP-users] Re: Fwd: Adding a Window block to an RFNOC graph

[Marcus D. Leech]

On 2021-10-23 5:58 p.m., Ivan Zahartchuk wrote:

I want to create FPGA firmware for USRP E310 with window function but I get the error I described above. My yaml file is also attached above. I need to do windowing and FFT on the FPGA side. And understand why FFT returns zero values even when it is configured to produce complex data.

    There are two distinct problems described here.  One is that for
    very-small input values, the FFT produces zero outputs. This is very
    likely due to the
       fact that the FFT implementation in the FPGA is an integer
    implementation, with fixed precision.  If it's scaling the output
    appropriately for
       mag**2, there will be cases where it produces zeros.   You can
    either increase the RF gain, or, as I *THINK* you're trying to do,
    use the window
       function to artificially boost the input amplitudes prior to the
    FFT computation?
    
    Unfortunately, I don't personally have an RFNOC toolchain myself, so
    I can't offer much in the way of advice on the build error you're
    getting, and I'm
      hoping someone with more RFNOC-on-E310 experience can be of more
    help.

пт, 22 окт. 2021 г. в 17:55, Marcus D. Leech <patchvonbraun@gmail.com>:

On 2021-10-22 6:05 a.m., Ivan Zahartchuk wrote:

Yes I am setting fft for magnitudes. On the front side, I am doing a log. I perfectly understand where infinity comes from. I don’t understand why the FFT returns 0. But how can I configure the Window?

What does uhd_usrp_probe show in the "RFNOC Blocks" section on this device?

I think the window RFNOC function in GNu Radio takes a list of the window values as a parameter--you can populate that with any of the window.* functions
  within Gnu Radio.

пт, 22 окт. 2021 г. в 01:51, Marcus D. Leech <patchvonbraun@gmail.com>:

On 2021-10-21 6:40 p.m., Ivan Zahartchuk wrote:

Hello, I have a problem that when receiving samples from the USRP E310 board, after the FFT block at low gain, zero values are received. After that I log them and get infinity. I wanted to figure out what the problem is, but I have no idea, maybe the Window block will fix the situation. But when building my yaml file, I get the error:
[ERR] 2 Unresolved connection(s)
[ERR]     (window0-out_0 -> fft0-in0)
[ERR]     (fft0-out_0 -> ep1-in_0)
[INF]         (('radio0', 'ctrl_port', 'master'),)
[INF]         (('radio0', 'time_keeper', 'listener'),)
[INF]         (('radio0', 'x300_radio', 'slave'),)
[INF]         (('_device_', 'ctrlport_radio', 'slave'),)
[INF]         (('_device_', 'time_keeper', 'broadcaster'),)
[INF]         (('_device_', 'x300_radio', 'master'),)
Please tell me what could be the problem and how can I add the Window block to my image?

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Do you have your FFT configured for log output?  Because the logarithm of zero is undefined.

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