Custom constellation scheme

[Roman A Sandler]

Hi,

I am currently using `digital.generic_mod` with the included modulation
scheme from
https://www.gnuradio.org/doc/sphinx-3.7.1/digital/constellations.html
<https://signtr.website/click?redirect=https%3A%2F%2Fwww.gnuradio.org%2Fdoc%2Fsphinx-3.7.1%2Fdigital%2Fconstellations.html&dID=1588891460577&linkName=https://www.gnuradio.org/doc/sphinx-3.7.1/digital/constellations.html>
(e.g. digital.constellation_8psk, digital.constellation_16qam,
etc...) as such:

```
digital_constellation_modulator = digital.generic_mod(


constellation=digital.constellation_bpsk().base(),
                                        differential=False,
                                        samples_per_symbol=sps,
                                        pre_diff_code=True,
                                        excess_bw=excess_bw,
                                        verbose=False,
                                        log=False)

```

However, I would like to use modulation schemes which are not included in
digital. I have two questions in that regard:

1) How can I define my own phase-amplitude type modulation schemes such as
4PAM, 64QAM which are not included by default?
2) Can I use digital.generic_mod with FSK type modulations like GFSK? If
not how would I use them?

Thanks,
Roman