DSP VS gnuradio

Right now I have a trapezoidal filter core (written in Verilog) created by a colleague that I know has been used with success in the past. So, starting from a simple ADC to DAC project provided by another Red Pitaya user, Pavel (here), I placed the core into the block design in between the ADC and DAC as such, let Vivado do its thing, and generated a bitstream without error (note that trap_0 has S00_AXIS data width 16, so it only takes the 16 LSB from the ADC, which I believe is from adc_dat_a_i). All of the source code for the trapezoidal filter core can be found on GitHub (top core and dependencies).

In gr-dtv transmitter examples for Gnuradio, I see some times people use a resampler block before the RF hardware sink. Say our sampling rate is ~9.14Msps which satisfies the Nyquist criterion because our samples are complex numbers.

2.1. Thanks for that tip, I forgot that I was able to check the source code of the WBFM Receive block. As you have said, there are mostly the same. There are some differences between how values are picked. The WBFM Receive block would be a synonym of Quadrature demod => Fir Filter (decimation => Low pass filter) => FM Deemphasis. 2.3. My question there is why 10 and not 20 or 100. I understand that the idea is to reduce the sample rate asap, but what I don't understand is why those values were picked and how can I understand what would be the "correct" or "best" value. 2.4. I'm not fully understanding what you said. If I check the WB FM recieve source code the values that are supplied as the cutoff freq and transition width of the Low pass filter differ from the one of the example. The webfm would apply a sample rate / decimation / 2 - sample rate / decimation / 32 as a cutoff freq and a sample rate / decimation / 32 as a transition transition width. Calculating those values would end up in different that the ones supplied in this second example. Again, is there a rule of thumb to pick these values?.

Gaussian filter is used only on the tx side, so specifying bt in the receiver makes no sense. Take a look at gfsk mod/demod blocks implementation: https://github.com/gnuradio/gnuradio/blob/master/gr-digital/python/digital/gfsk.py

GNU Radio

Here's the filter coefficients used for the GNU-Radio interpolator block to get you started. This is a 7th order interpolator (i.e., 8 FIR taps) with very good performance. Each "row" of the array sets the delay in steps of sample_time / 128.

From their README: “open-source software development toolkit that provides signal processing blocks to implement software radios.” https://github.com/gnuradio/gnuradio