New pm3py/lf/fsk.py — a function-for-function Python port of the Proxmark FSK
stack (firmware/common/lfdemod.c): fsk_wave_demod (count samples between 0->1
transitions: short wave = fc/8, long = fc/10) + aggregate_bits (runs -> clock-
resolution bits) = fskdemod, plus preamble_search, HIDdemodFSK, detectAWID hooks.
Ported to track the C reference (and thus real-tag output), not reinvented.
protocols.decode_hid: FSK2a + Manchester -> Wiegand. Format is told by frame
structure, not parity alone — the 26-bit H10301 wire frame carries a 0x20 header
at bit 37 + a sentinel 1 at bit 26 (per firmware add_HID_preamble); the 37-bit
H10304 frame is header-less (37-bit Manchester count, no 0x20). Each candidate is
still parity-validated by re-encoding through the shipped HIDProxTag, so a false
alignment can't slip through. Added to the identify decoder chain after EM4100.
Synthetic HID tests build the real add_HID_preamble framing (header+sentinel for
26-bit, bare 37-bit) and render fc/8/fc/10 square waves, so a green test means the
demod inverts what a real HID card / PM3 sim emits. Full suite 1232 green.
AWID (96-bit) framing decode + PSK/Indala + biphase/FDX-B queued next.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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