[Discuss-gnuradio] Modulation/Demodulation Blocks' Function details

[Frederick Lee]

Hi GNURadio community,

I'm looking into how the modulation and demodulation blocks work. Specifically the BPSK mod and demod blocks. Here is a list of the files I looked through and the location:

generic_mod_demod.py - */gr-digital/python
modulation_utils.py - */gr-digital/python
bpsk.py - */gr-digital/python
digital_constellation.h - */gr-digital/include
digital_constellation.cc - */gr-digital/lib
digital_swig.py - */build/gr-digital/swig

gr_phase_modulator_fc.h - */gnuradio-core/src/lib/general
gr_phase_modulator_fc.cc - */gnuradio-core/src/lib/general

digital_gmskmod_bc.h - */gr-digital/include
digital_gmskmod_bc.cc - */gr-digital/lib

gr_diff_encoder_bb.h - */gnuradio-core/src/lib/general        for differntialBPSK
gr_diff_encoder_bb.cc - */gnuradio-core/src/lib/general        for differntialBPSK

gr_unpack_k_bits_bb.h - */gnuradio-core/src/lib/general
gr_unpack_k_bits_bb.cc - */gnuradio-core/src/lib/general

Are there any other files I should look at the get an understanding what happens to the bits?

In the generic_mod_demod.py file, I come across functions like

digital.map_bb(mod_codes.invert_code(self._constellation.pre_diff_code()))

and I find the function map_bb in the digital_swig.py file. But the only code there is

return _digital_swig.map_bb(*args, **kwargs)

I can't find anything on _digital_swig no matter where I look. _digital_swig was set to something at the beginning of the file, but I couldn't understand it. Can someone tell me where to look to find the source code for the _digital_swig.maps_bb() and the _digital_swig.pfb_clock_sync_ccf() functions?

Also another thing I've been wondering is why is there the DIGITAL_API in some lines. For example,
class DIGITAL_API digital_constellation : public boost::enable_shared_from_this<digital_constellation>
What is the point of DIGITAL_API?

Thanks a lot,
Frederick