pre uc480 integration

left_off.md

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+# Session summary — scan timeout & geometry fixes
+
+## Bug fixed: oscilloscope timeout on first row
+
+**File:** `hardware/tektronix_base.py` — `transfer_fastframe()` (~line 1414)
+
+The scope was configured for N frames but only triggered on fewer (e.g. 57 of 58) because
+the stage decelerates before the last laser pulse. `transfer_fastframe` looped using
+`get_fastframe_count()` (the configured maximum), so the final `read_raw()` call blocked
+waiting for data that never came and timed out.
+
+**Fix:** replaced `get_fastframe_count()` with a live query:
+```python
+acquired = int(self.query("ACQuire:NUMFRAMESACQuired?"))
+```
+The loop now reads exactly as many frames as the scope actually captured.
+
+---
+
+## Scan geometry overhaul
+
+**File:** `sc3_aui_app.py`
+
+### Constants added (near line 71)
+```python
+LASER_FREQ_HZ = 2000.0          # fixed laser pulse frequency
+SCAN_RAMP_MM  = v² / (2a)       # ≈ 3.33 mm  (100² / 2×1500)
+```
+`SCAN_RAMP_MM` is the distance the stage needs to accelerate from rest to full scan
+velocity, or decelerate back to rest.
+
+### `_run_scan()` changes
+- `points_per_row` now uses `LASER_FREQ_HZ` instead of the param-supplied `laser_freq`.
+- Pre-scan X position is `x_start - SCAN_RAMP_MM` so the stage arrives at `x_start`
+  already at full velocity (TRIGOUT_MAXV fires at the right place).
+- Scan move ends at `x_start + x_delta + SCAN_RAMP_MM` so the stage doesn't begin
+  decelerating until after the last data point.
+
+### Travel-limit guards added (before any hardware interaction)
+Raises `ValueError` with an actionable message if the extended move would exceed the
+stage limits baked into the driver (`bbd20x.py`: X 0–110 mm, Y 0–75 mm):
+- `x_start - SCAN_RAMP_MM < 0`
+- `x_start + x_delta + SCAN_RAMP_MM > 110`
+- any Y row position outside 0–75 mm
+
+Error messages tell the user exactly how many mm to adjust.
+
+---
+
+## What to check / next steps
+- Verify `ACQuire:NUMFRAMESACQuired?` is the correct query string for the specific scope
+  model in use (MDO/MSO series assumed; confirm against programmer manual).
+- `LASER_FREQ_HZ = 2000.0` is a temporary constant — wire it to the UI param when ready.
+- Confirm `SCAN_RAMP_MM` matches observed stage behaviour; if the BBD202 velocity profile
+  is not perfectly triangular the empirical ramp may differ slightly from v²/2a.