report sensor freshness in captures

docs/axis-validation-2026-08-16.md

@@ -54,5 +54,7 @@ in firmware.
 - Earlier side-to-side orientation changes were Y-dominant, confirming the
   remaining gyro axis.
 
-The mounted sensor axes and the firmware's enclosure-frame mapping are
+The mounted sensor axes and the firmware's enclosure-frame axis assignments are
-consistent.
+consistent. These tests established the dominant gyro axis but did not establish
+gyro polarity; directed positive and negative rotations remain part of the
+calibration pass.

tools/capture_serial.py

@@ -30,6 +30,15 @@ EXPECTED_COLUMNS = [
     "loop_overrun_count",
 ]
 
+ACCEL_STATUS_INDEX = EXPECTED_COLUMNS.index("accel_int_source")
+GYRO_STATUS_INDEX = EXPECTED_COLUMNS.index("gyro_status")
+LOOP_OVERRUN_INDEX = EXPECTED_COLUMNS.index("loop_overrun_count")
+
+ACCEL_DATA_READY_MASK = 0x80
+ACCEL_OVERRUN_MASK = 0x01
+GYRO_DATA_READY_MASK = 0x08
+GYRO_OVERRUN_MASK = 0x80
+
 
 def parse_args() -> argparse.Namespace:
     parser = argparse.ArgumentParser()
@@ -85,6 +94,11 @@ def main() -> int:
     timing_anomaly_count = 0
     ignored_line_count = 0
     rejected_record_count = 0
+    accel_stale_count = 0
+    accel_overrun_count = 0
+    gyro_stale_count = 0
+    gyro_overrun_count = 0
+    final_loop_overrun_count = 0
     previous_sequence = None
     previous_timestamp_us = None
     print(f"Recording {port} to {output}; press Ctrl-C to stop", flush=True)
@@ -123,6 +137,19 @@ def main() -> int:
 
                 sequence = values[0]
                 timestamp_us = values[1]
+                accel_status = values[ACCEL_STATUS_INDEX]
+                gyro_status = values[GYRO_STATUS_INDEX]
+                final_loop_overrun_count = values[LOOP_OVERRUN_INDEX]
+
+                if not accel_status & ACCEL_DATA_READY_MASK:
+                    accel_stale_count += 1
+                if accel_status & ACCEL_OVERRUN_MASK:
+                    accel_overrun_count += 1
+                if not gyro_status & GYRO_DATA_READY_MASK:
+                    gyro_stale_count += 1
+                if gyro_status & GYRO_OVERRUN_MASK:
+                    gyro_overrun_count += 1
+
                 if previous_sequence is not None:
                     expected_sequence = (previous_sequence + 1) & 0xFFFFFFFF
                     if sequence != expected_sequence:
@@ -159,6 +186,13 @@ def main() -> int:
         f"saved {output}",
         flush=True,
     )
+    print(
+        f"Status totals: accel_stale={accel_stale_count}, "
+        f"accel_overrun={accel_overrun_count}, gyro_stale={gyro_stale_count}, "
+        f"gyro_overrun={gyro_overrun_count}, "
+        f"acquisition_loop_overruns={final_loop_overrun_count}",
+        flush=True,
+    )
     return 0