Add

csv_preprocessor.py

@@ -55,6 +55,12 @@ LP_LOW_HS_ONSET_MARGIN_NS = 20.0  # ns
 # LP-low plateau below this → SoT sequence too brief for receiver to detect → flicker risk
 FLICKER_LP_LOW_MAX_NS = 50.0  # ns
 
+# Mode G: LP-low significantly shorter than the baseline seen on this hardware.
+# Normal LP-low (THS_PREPARE + THS_ZERO + preamble HS-0 symbols) measures ~379–380 ns.
+# Flicker-associated short LP-low values cluster at 34–194 ns (confirmed: cap 27 at 108 ns).
+# The gap between 194 and 379 ns is unambiguous — 250 ns splits the populations cleanly.
+LP_LOW_FLICKER_THRESHOLD_NS = 250.0  # ns — below this, LP-low is suspiciously short
+
 # CLK lane LP-00 minimum for SN65DSI83 CLK lane lock (TCLK_PREPARE + TCLK_ZERO ≥ 300 ns)
 CLK_LP_LOW_MIN_NS = 300.0
 
@@ -69,10 +75,13 @@ HS_BURST_AMPLITUDE_MIN_MV = 40.0  # mV — below this, no real HS burst is prese
 # Measures fraction of post-LP-low window (100 ns margin, 3 µs look-ahead) where rolling_std
 # exceeds HS_OSC_STD_V.  With dynamic video at 432 Mbps DDR each bit spans ~4.6 ns; transitions
 # (~1 ns) fire the 1 ns rolling window ~20% of the time → healthy HS → osc_frac ≈ 0.14–0.22.
-# Blanking/control packets carry uniform data → osc_frac ≈ 0.00–0.02 (confirmed NOT flicker).
-# Partial or transient HS dropout sits between these bands → suspicious → send to Claude.
+# Static solid-colour content (e.g. FF 33 BB repeating) has fewer bit transitions, so healthy
+# osc_frac is lower: ~0.11–0.17.  Blanking/control packets → osc_frac ≈ 0.00–0.02 (normal).
+# Confirmed partial/transient HS dropout (Apr-23, cap 0105): osc_frac = 0.079.
+# Suspicious zone must sit below the lowest healthy static-pink value (~0.11) and above true
+# dropout values (~0.04–0.08).  Threshold set to 0.10 to give clear separation.
 HS_OSC_FRACTION_SUSPICIOUS_LO = 0.04   # below this: dead HS — blanking / control (normal)
-HS_OSC_FRACTION_SUSPICIOUS_HI = 0.13   # above this: healthy HS; between bands → flag
+HS_OSC_FRACTION_SUSPICIOUS_HI = 0.10   # above this: healthy HS; between bands → flag
 
 
 # Mode A minimum amplitude: LP-11-return edge artifacts produce near-zero amplitude in the
@@ -809,6 +818,9 @@ class LPMetrics:
                          + (f"  avg {self.hs_burst_dur_ns:.0f} ns" if self.hs_burst_dur_ns else ""))
         if self.hs_amplitude_mv is not None:
             lines.append(f"  HS amplitude    : {self.hs_amplitude_mv:.0f} mV (single-ended p-p/2)")
+        if self.hs_osc_fraction is not None:
+            lines.append(f"  HS osc fraction : {self.hs_osc_fraction:.4f}  "
+                         f"(suspicious {HS_OSC_FRACTION_SUSPICIOUS_LO:.2f}–{HS_OSC_FRACTION_SUSPICIOUS_HI:.2f})")
         if self.flicker_suspect:
             if not self.lp_transition_valid and not self.lp11_voltage_v:
                 lines.append(
@@ -823,6 +835,20 @@ class LPMetrics:
                     f"(amplitude {self.hs_amplitude_mv:.0f} mV < {HS_BURST_AMPLITUDE_MIN_MV:.0f} mV, "
                     f"lp11_to_hs={self.lp11_to_hs_ns:.0f} ns) ***"
                 )
+            elif (self.hs_osc_fraction is not None
+                    and HS_OSC_FRACTION_SUSPICIOUS_LO < self.hs_osc_fraction < HS_OSC_FRACTION_SUSPICIOUS_HI):
+                lines.append(
+                    f"  *** FLICKER SUSPECT: partial HS dropout "
+                    f"(osc_frac={self.hs_osc_fraction:.4f} in suspicious "
+                    f"{HS_OSC_FRACTION_SUSPICIOUS_LO:.2f}–{HS_OSC_FRACTION_SUSPICIOUS_HI:.2f} zone) ***"
+                )
+            elif (self.lp_low_duration_ns is not None
+                    and self.lp_low_duration_ns < LP_LOW_FLICKER_THRESHOLD_NS):
+                lines.append(
+                    f"  *** FLICKER SUSPECT: short LP-low "
+                    f"({self.lp_low_duration_ns:.0f} ns vs ~380 ns normal — "
+                    f"bridge may miss SoT) ***"
+                )
             else:
                 lines.append(
                     f"  *** FLICKER SUSPECT: LP-low plateau absent or < {FLICKER_LP_LOW_MAX_NS:.0f} ns ***"
@@ -1066,6 +1092,14 @@ def analyze_lp_file(path: Path) -> "LPMetrics":
         and hs_osc_fraction is not None
         and HS_OSC_FRACTION_SUSPICIOUS_LO < hs_osc_fraction < HS_OSC_FRACTION_SUSPICIOUS_HI
     )
+    # Mode G: LP-low plateau present but much shorter than the ~380 ns baseline.
+    # Indicates insufficient THS_PREPARE+THS_ZERO (or preamble) for the bridge to lock
+    # the data lane SoT — the bridge likely misses the first few pixels of the line.
+    mode_g_short_lp_low = (
+        lp_transition_valid
+        and lp_low_duration_ns is not None
+        and lp_low_duration_ns < LP_LOW_FLICKER_THRESHOLD_NS
+    )
     flicker_suspect = (
         channel == "dat"
         and (
@@ -1076,6 +1110,7 @@ def analyze_lp_file(path: Path) -> "LPMetrics":
                     lp_low_duration_ns is None
                     or hs_burst_absent
                     or mode_f_partial_hs
+                    or mode_g_short_lp_low
                 )
             )
         )