nx_bfsk.nx

nx_bfsk.nx -- Binary Frequency Shift Keying modem. Apparatus substrate piece between the codec layer (bytes) and the radio layer (samples). Integer-only, Q10 phase, square-wave reference signals for fully-bits-up correlator demodulation. Doctrinal stance: this is the primitive that lets NishiVoice frames modulate onto an HF carrier driving a ground dipole, or onto a UHF carrier driving a chirp-spread-spectrum mesh. No external DSP library; the modulator IS the math; the demod IS the math. Math (public domain since Hartley 1928): bit 0 -> N samples of a square wave at frequency f0 bit 1 -> N samples of a square wave at frequency f1 demod -> correlate received samples against reference square wave at f0 and f1; pick whichever correlation is larger. Phase accumulator is Q10 (1024 units per period), so phase_inc_q10 for frequency f at sample rate fs = round(f * 1024 / fs). At fs= 8000 and f0=1200, phase_inc_0 = 154; at f1=2200, phase_inc_1=282. genealogy_id: hartley_1928_modulation + bell_202_1962_fsk_audio + nx_voice_codec_v1_q10 lineage_id: nishi_bfsk_q10