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https://github.com/NawfalMotii79/PLFM_RADAR.git
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Jason
c30be89dbe
Adds tb/cosim/fpga_reference.py: numpy/scipy implementation of NCO,
FFT, matched filter, and Doppler. Unlike fpga_model.py — which is a
bit-exact PORT of the RTL (same NCO_SINE_LUT, same twiddle .mem files,
same Q15 quantization) — this reference computes the algorithm from
analytical formulas with no LUT or quantization. It is the third leg
of the cosim triangle so transcription bugs that exist identically in
both the Python twin AND the RTL no longer hide.
Adds tb/cosim/compare_independent.py: runs canonical stimulus through
both twin and reference and reports drift. Bytewise LUT spot-checks
(NCO_SINE_LUT, fft_twiddle_16.mem, fft_twiddle_2048.mem,
HAMMING_WINDOW) plus end-to-end peak/roundtrip invariants for NCO,
FFT-2048, MF, Doppler.
Findings (12/13 drift checks pass):
* NCO_SINE_LUT, fft_twiddle_16.mem, fft_twiddle_2048.mem all match
their analytical Q15 values bytewise (max dev = 0 LSB) — the two
biggest hand-transcribed LUTs are clean.
* HAMMING_WINDOW [FAIL] — max 740 LSB drift from documented formula
0.54-0.46*cos(2*pi*n/15) at n=5 (LUT=25971, ideal=25231). The
same wrong values appear in fpga_model.HAMMING_WINDOW and
doppler_processor.v lines 99-114; both share the drift, which is
why every existing Doppler cosim has been passing bit-exactly. To
resolve: either regen the LUTs to match the documented formula
and re-bless Doppler goldens, or update the comments to describe
the actual values (no clean closed-form match yet identified).
Not wired into run_regression.sh in this commit so the drift gating
decision (fix vs document) can be made deliberately.