Bug: 16-bit detect_count was reset only on power-on; increments at three
sites (ST_IDLE/ST_BUFFER simple-threshold paths and ST_CFAR_CMP) accumulate
across frames. At 178 fps with even 2-3 average detections per frame the
counter wraps in 100-180 seconds, breaking any rate-based host telemetry
or health check that reads it.
Fix: add `detect_count <= 16'd0` in ST_DONE so the counter represents
"detections this frame" instead of cumulative-since-boot. Updated $display
wording from "total detections" to "frame detections".
T13 flipped from "count keeps growing" to "identical-scene frames produce
identical counts" (the actual contract a per-frame counter must satisfy).
TB snapshots detect_count during ST_DONE because cfar_busy only goes low
on ST_IDLE entry — after the reset has fired.
Verification: tb_cfar_ca 24/24 PASS, quick regression 31/31 PASS.
Note: detect_count output port is now "live" (accumulates during frame,
0 between frames). Audit confirmed no current host telemetry consumes
this port. If future host code needs a stable last-frame total, add a
detect_count_last_frame snapshot register then.
AUDIT-C12: usb_data_interface_ft2232h had a misleading single-buffer comment
that overstated the timing slack and referenced a frame_ack_toggle CDC that
was never implemented. Re-verified actual numbers: at 178 fps the slack is
1.14 ms (20%), not "much shorter than gap". No data corruption today (write
order matches read order, addresses don't collide), but frame_complete
firing while WR_FSM is still draining the previous frame causes silent
frame drops via the missed frame_ready_toggle edge.
Fix is instrumentation, not architectural rework: add wr_done_toggle
(ft_clk -> clk CDC) on WR_DONE -> WR_IDLE, track frame_pending in clk
domain, count drops in 7-bit saturating frame_drop_count, surface in
unused upper 7 bits of status_words[5]. Host now has visibility into the
failure mode if margin ever shrinks (faster frame rate or USB bandwidth
shortfall). Replaced misleading comment with corrected timing breakdown.
AUDIT-S22: cfar_ca emits one detection per 3 cycles (THR/MUL/CMP); the
detection RMW takes 3 cycles. Match by construction today, fragile against
any CFAR speedup. Added a header comment in cfar_ca.v documenting the
dependency, and a SIMULATION-only assertion in usb_data_interface_ft2232h.v
that fires [ASSERT FAIL] AUDIT-S22 if cfar_valid arrives while RMW busy.
Catches silent-drop regressions in the test suite.
Verification: new tb_ft2232h_frame_drop.v with 5 scenarios (no drops /
stalled drops / multi-drop / recovery / saturation at 127) - 10/10 PASS.
Quick regression 31/31 PASS (was 30/30; +1 new test, 0 regressions).
FPGA — RX chain
matched_filter_multi_segment.v: drop the gratuitous /4 scaling on
DDC sign-extended input (was ddc_i[17:2] + ddc_i[1]); use
ddc_i[15:0] directly. fft_engine has INTERNAL_W=32 with
saturating 16-bit output, so full 16-bit input is safe. Restores
~12 dB of MF input dynamic range.
radar_receiver_final.v: remove latency_buffer (count-N-pulses-then-
prime FIFO that left frame 1 with all-zero ref). Replaced with
a single-FF alignment register on ref_i/ref_q that matches the
1-FF stage multi_segment ST_PROCESSING uses on adc_data.
Verified by tb/tb_rxb_fullchain_latency.v — autocorrelation peak
at bin 0 with peak/mean ~88x.
doppler_processor.v / mti_canceller.v / cfar_ca.v /
range_bin_decimator.v / radar_receiver_final.v / radar_system_top.v
/ usb_data_interface_ft2232h.v: switch port and parameter widths
from RP_NUM_RANGE_BINS / RP_RANGE_BIN_BITS (always 512 / 9-bit)
to RP_MAX_OUTPUT_BINS / RP_RANGE_BIN_WIDTH_MAX (auto-scales:
50T 512 / 9-bit, 200T 4096 / 12-bit). Unblocks 200T 20 km mode
at the RX module boundary; USB wire-protocol extension still
pending.
radar_receiver_final.v: doppler_frame_done_prev reset value 0 -> 1
to prevent false done pulse on cycle 1 when level signal is
HIGH at reset.
matched_filter_processing_chain.v: delete the broken `ifdef
SIMULATION inline behavioural FFT (482 lines removed). It
produced wrong-bin peaks and 100-1000x weak magnitudes. Chain
now uses production fft_engine.v + frequency_matched_filter.v
in both iverilog and Vivado. Iverilog tests are ~38x slower per
chain pass but produce correct results. Misleading "OK with
Xilinx IP" comments at three test sites updated since the FFT
is in-house, not an IP placeholder.
FPGA — testbenches
tb/tb_rxb_latency_measure.v (new): measures chain internal pipeline
depth (~2057 cycles, chirp-agnostic).
tb/tb_rxb_fullchain_latency.v (new): full-chain autocorrelation
verification — drives ddc with the same chirp samples the loader
serves as ref, finds peak position and peak/mean.
tb/tb_matched_filter_processing_chain.v: wait timeouts bumped
50000 -> 500000 cycles to accommodate production FFT pipeline.
MCU
main.cpp checkSystemHealthStatus: latch system_emergency_state on
the error_count > 10 path so the SAFE-MODE blink loop in main()
actually engages (was bypassed because predicate was false).
main.cpp: move FPGA reset BEFORE the if(PowerAmplifier) block so
adar_tr_x is driven LOW (RX commanded externally) before PA Vdd
reaches 22 V. Old reset block at the original location removed.
main.cpp MX_GPIO_Init: add GPIO_PIN_12 (FPGA reset) to the
explicit WritePin(LOW) list so the safe initial state is no
longer implicit.
main.cpp checkSystemHealth: rate-limit ADAR1000
verifyDeviceCommunication (HAL_Delay 1ms x 4 devices = 4 ms
blocking SPI burst per main-loop iteration) from every-loop to
every 2 s. readTemperature stays per-loop so over-temp
detection latency is unchanged.
USBHandler.cpp processSettingsData: dispatch threshold bumped
74 -> 82 (matches parser minimum); buffer drained after parse
attempt (slide remaining bytes left) so a false END find no
longer sticks the buffer until 256-byte overflow.
GUI
radar_protocol.py: NUM_RANGE_BINS 64 -> 512 (matches FPGA
RP_NUM_RANGE_BINS); NUM_CELLS 2048 -> 16384.
radar_protocol.py _ingest_sample: honor FPGA frame_start bit for
resync after a USB drop; capture range_profile[rbin] once per
range bin at dbin == 0 (FPGA emits the same range_i/range_q for
all 32 Doppler cells of a given range bin; previous accumulator
inflated the profile 32x).
v7/models.py RadarSettings: range_resolution 24 -> 6 m (matches
c/(2*100MHz)*4); max_distance and coverage_radius 1536 -> 3072 m;
map_size 2000 -> 4000.
v7/models.py WaveformConfig: n_range_bins 64 -> 512, fft_size
1024 -> 2048, decimation_factor 16 -> 4.
GUI_V65_Tk.py: _RANGE_PER_BIN math and stale "~24 m / ~1536 m"
comments updated.
test_v7.py: assertion values updated to match new defaults.
Tests
test_ddc_cosim_fuzz.py: remove unused os/tempfile imports, wrap
three long lines for ruff E501 compliance.
Split ST_CFAR_THR into two pipeline stages (THR + MUL) to fix Build 23
timing violation (WNS = -0.309 ns). The combinational path from
leading_sum through GO/SO cross-multiply into alpha*noise DSP was too
long for 10 ns.
New pipeline:
ST_CFAR_THR: register noise_sum_comb (mode select + cross-multiply)
ST_CFAR_MUL: compute alpha * noise_sum_reg in DSP
ST_CFAR_CMP: compare + update window (unchanged)
3 cycles per CUT instead of 2 (~85 us vs 70 us per frame, negligible).
All detection results identical: 23/23 CFAR standalone, 22/22 full
regression, 3/3 real-data co-sim (5137/5137 exact match) PASS.
Jason