updates

csv_preprocessor.py

@@ -811,10 +811,11 @@ def analyze_lp_file(path: Path) -> "LPMetrics":
         if hs_bursts:
             s, e, _ = hs_bursts[0]
             burst_volts = volts[s:e]
-            hs_amplitude_mv = round(
-                (float(np.percentile(burst_volts, 95)) -
-                 float(np.percentile(burst_volts, 5))) / 2 * 1000, 1
-            )
+            if len(burst_volts) >= 2:
+                hs_amplitude_mv = round(
+                    (float(np.percentile(burst_volts, 95)) -
+                     float(np.percentile(burst_volts, 5))) / 2 * 1000, 1
+                )
 
     # ── Warnings ─────────────────────────────────────────────────────────
     warnings = []
@@ -842,27 +843,34 @@ def analyze_lp_file(path: Path) -> "LPMetrics":
             warnings.append("No HS bursts detected after LP transition")
 
     # Flicker suspect: either the LP-low plateau is absent/short, OR the HS burst
-    # amplitude is too low (indicating the HS burst never actually started).
+    # amplitude is too low.  Two confirmed failure modes on this hardware:
     #
-    # The second condition catches the confirmed failure mode on this hardware:
-    #   LP-11 → LP-01/LP-00 preamble (normal ~342 ns) → bridge misses SoT
-    #   → driver returns to LP-11 without entering HS mode
-    #   → burst window is DC LP-11, hs_amplitude ≈ 15–30 mV (vs normal 105–122 mV).
-    # In this case lp_low_duration_ns = ~342 ns (above threshold), so the LP-low
-    # check alone produces a false negative.
+    #   A) Normal LP-low (~342–380 ns) → bridge misses SoT → returns to LP-11
+    #      Signature: lp11_to_hs fires at real LP-low end (~347 ns), hs_amplitude ≈ 15–30 mV.
+    #      Guard: lp11_to_hs >= LP_LOW_DUR_MIN_NS prevents DC-content false positives
+    #      where the ~3 ns noise spike fires the gate but HS IS present.
+    #
+    #   B) Short LP-low (50–200 ns, vs nominal ~342–380 ns) → marginal SoT timing
+    #      → HS burst starts but is weak, hs_amplitude ≈ 40–60 mV (vs normal 100–122 mV).
+    #      Signature: lp_low anomalously short, lp11_to_hs fires at noise spike (~3 ns).
+    #      The lp11_to_hs guard cannot be used here (noise spike looks the same as mode A
+    #      false positives), so LP-low duration itself gates the amplitude check.
+    #      Confirmed example: capture 0120 (lp_low=108 ns, lp11_to_hs=1.7 ns, amp=49 mV).
     #
     # Only flag DAT lane (CLK is continuous HS — LP states not expected).
-    # Guard: require lp11_to_hs_ns >= LP_LOW_DUR_MIN_NS to rule out the consistent
-    # ~3 ns noise spike at LP-11 exit.  On good captures the rolling-std gate fires
-    # at ~3 ns (hardware artifact); on confirmed flicker it fires at ~347 ns (real
-    # LP-low completes, then HS never starts → bridge returns to LP-11).
-    # Without this guard, DC-like HS data (uniform display content) produces low
-    # amplitude on otherwise good captures and causes false positives.
+    _lp_low_short = (
+        lp_low_duration_ns is not None
+        and lp_low_duration_ns < 200.0   # below this, LP-low is anomalously brief
+    )
     hs_burst_absent = (
         hs_amplitude_mv is not None
         and hs_amplitude_mv < HS_BURST_AMPLITUDE_MIN_MV
-        and lp11_to_hs_ns is not None
-        and lp11_to_hs_ns >= LP_LOW_DUR_MIN_NS
+        and (
+            # Mode A: LP-low normal, HS never started (rolling-std confirms it)
+            (lp11_to_hs_ns is not None and lp11_to_hs_ns >= LP_LOW_DUR_MIN_NS)
+            # Mode B: LP-low anomalously short + low amplitude = marginal HS launch
+            or _lp_low_short
+        )
     )
     flicker_suspect = (
         channel == "dat"