Merge pull request 'feat: systemd auto-start for ROS2 + dashboard on Orin boot (bd-1hyn)' (#732) from sl-perception/bd-1hyn-orin-autostart into main

Extends the bd-66hx serial protocol with two new Orin→ESP32 commands:
  CMD_OTA_CHECK  (0x10): triggers gitea_ota_check_now(), responds with
    TELEM_VERSION_INFO (0x84) for Balance and IO (current + available ver).
  CMD_OTA_UPDATE (0x11): uint8 target (0=balance, 1=io, 2=both) — triggers
    uart_ota_trigger() for IO or ota_self_trigger() for Balance.
    NACK with ERR_OTA_BUSY or ERR_OTA_NO_UPDATE on failure.
New telemetry: TELEM_OTA_STATUS (0x83, target+state+progress+err),
  TELEM_VERSION_INFO (0x84, target+current[16]+available[16]).
Wires OTA stack into app_main: ota_self_health_check on boot,
  gitea_ota_init + ota_display_init after peripherals ready.
CMakeLists updated with all OTA component dependencies.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/plans/zany-hugging-oasis.md

@@ -0,0 +1,308 @@
+# Issue #469: Terrain Classification Implementation Plan
+
+## Context
+
+SaltyBot currently has good sensor infrastructure (IMU, cameras, RealSense) and a robust velocity control system with the `VelocityRamp` class. However, it lacks terrain awareness for surface type detection and speed adaptation. This feature will enable:
+
+1. **Surface detection** via IMU vibration analysis and camera texture analysis
+2. **Automatic speed adaptation** based on terrain type and roughness
+3. **Terrain logging** for mapping and future learning
+4. **Improved robot safety** by reducing speed on rough/unstable terrain
+
+## Architecture Overview
+
+The implementation follows the existing ROS2 patterns:
+
+```
+IMU/Camera Data
+    ↓
+[terrain_classifier_node]  ← New node
+    ↓
+/saltybot/terrain_state (TerrainState.msg)
+    ↓
+[terrain_speed_adapter_node]  ← New node
+    ↓
+Adjusted /cmd_vel_terrain → existing cmd_vel_bridge
+    ↓
+Speed-adapted robot motion
+
+Parallel: [terrain_mapper_node] logs data for mapping
+```
+
+## Implementation Components
+
+### 1. **Message Definition: TerrainState.msg**
+**File to create:** `jetson/ros2_ws/src/saltybot_social_msgs/msg/TerrainState.msg`
+
+Fields:
+- `std_msgs/Header header` — timestamp/frame_id
+- `uint8 terrain_type` — enum (0=unknown, 1=pavement, 2=grass, 3=gravel, 4=sand, 5=indoor)
+- `float32 roughness` — 0.0=smooth, 1.0=very rough
+- `float32 confidence` — 0.0-1.0 classification confidence
+- `float32 recommended_speed_ratio` — 0.1-1.0 (fraction of max speed)
+- `string source` — "imu_vibration" or "camera_texture" or "fused"
+
+**Update files:**
+- `jetson/ros2_ws/src/saltybot_social_msgs/CMakeLists.txt` — add TerrainState.msg to rosidl_generate_interfaces()
+- `jetson/ros2_ws/src/saltybot_social_msgs/package.xml` — no changes needed (std_msgs already a dependency)
+
+### 2. **Terrain Classifier Node**
+**File to create:** `jetson/ros2_ws/src/saltybot_bringup/saltybot_bringup/terrain_classifier_node.py`
+
+**Purpose:** Analyze IMU and camera data to classify terrain type and estimate roughness.
+
+**Subscribes to:**
+- `/camera/imu` (sensor_msgs/Imu) — RealSense IMU at 200 Hz
+- `/camera/color/image_raw` (sensor_msgs/Image) — camera RGB at 15 Hz
+
+**Publishes:**
+- `/saltybot/terrain_state` (TerrainState.msg) — at 5 Hz
+
+**Key functions:**
+- `_analyze_imu_vibration()` — FFT analysis on accel data (window: 200 samples = 1 sec)
+  - Compute power spectral density in 0-50 Hz band
+  - Extract features: peak frequency, energy distribution, RMS acceleration
+  - Roughness = normalized RMS of high-freq components (>10 Hz)
+
+- `_analyze_camera_texture()` — CNN-based texture analysis
+  - Uses MobileNetV2 pre-trained on ImageNet as feature extractor
+  - Extracts high-level texture/surface features from camera image
+  - Lightweight model (~3.5M parameters, ~50-100ms inference on Jetson)
+  - Outputs feature vector fed to classification layer
+
+- `_classify_terrain()` — decision logic
+  - Simple rule-based classifier (can be upgraded to CNN)
+  - Input: [imu_roughness, camera_texture_variance, accel_magnitude]
+  - Decision tree or thresholds to classify into 5 types
+  - Output: terrain_type, roughness, confidence
+
+**Node Parameters:**
+- `imu_window_size` (int, default 200) — samples for FFT window
+- `publish_rate_hz` (float, default 5.0)
+- `roughness_threshold` (float, default 0.3) — FFT roughness threshold
+- `terrain_timeout_s` (float, default 5.0) — how long to keep previous estimate if no new data
+
+### 3. **Speed Adapter Node**
+**File to create:** `jetson/ros2_ws/src/saltybot_bringup/saltybot_bringup/terrain_speed_adapter_node.py`
+
+**Purpose:** Adapt cmd_vel speed based on terrain state and integration with velocity ramp.
+
+**Subscribes to:**
+- `/cmd_vel` (geometry_msgs/Twist) — raw velocity commands
+- `/saltybot/terrain_state` (TerrainState.msg) — terrain classification
+
+**Publishes:**
+- `/cmd_vel_terrain` (geometry_msgs/Twist) — terrain-adapted velocity
+
+**Logic:**
+- Extract target linear velocity from cmd_vel
+- Apply terrain speed ratio: `adapted_speed = target_speed × recommended_speed_ratio`
+- Preserve angular velocity (steering not affected by terrain)
+- Publish adapted command
+
+**Node Parameters:**
+- `enable_terrain_adaptation` (bool, default true)
+- `min_speed_ratio` (float, default 0.1) — never go below 10% of requested speed
+- `debug_logging` (bool, default false)
+
+**Note:** This is a lightweight adapter. The existing `velocity_ramp_node` handles acceleration/deceleration smoothing independently.
+
+### 4. **Terrain Mapper Node** (Logging/Mapping)
+**File to create:** `jetson/ros2_ws/src/saltybot_bringup/saltybot_bringup/terrain_mapper_node.py`
+
+**Purpose:** Log terrain detections with robot pose for future mapping.
+
+**Subscribes to:**
+- `/saltybot/terrain_state` (TerrainState.msg)
+- `/odom` (nav_msgs/Odometry) — robot pose
+
+**Publishes:**
+- `/saltybot/terrain_log` (std_msgs/String) — CSV formatted log messages (optional, mainly for logging)
+
+**Logic:**
+- Store terrain observations: (timestamp, pose_x, pose_y, terrain_type, roughness, confidence)
+- Log to file: `~/.ros/terrain_map_<timestamp>.csv`
+- Resample to 1 Hz to avoid spam
+
+**Node Parameters:**
+- `log_dir` (string, default "~/.ros/")
+- `resample_rate_hz` (float, default 1.0)
+
+### 5. **Launch Configuration**
+**File to update:** `jetson/ros2_ws/src/saltybot_bringup/launch/full_stack.launch.py`
+
+Add terrain nodes:
+```python
+terrain_classifier_node = Node(
+    package='saltybot_bringup',
+    executable='terrain_classifier',
+    name='terrain_classifier',
+    parameters=[{
+        'imu_window_size': 200,
+        'publish_rate_hz': 5.0,
+    }],
+    remappings=[
+        ('/imu_in', '/camera/imu'),
+        ('/camera_in', '/camera/color/image_raw'),
+    ],
+)
+
+terrain_speed_adapter_node = Node(
+    package='saltybot_bringup',
+    executable='terrain_speed_adapter',
+    name='terrain_speed_adapter',
+    parameters=[{
+        'enable_terrain_adaptation': True,
+        'min_speed_ratio': 0.1,
+    }],
+    remappings=[
+        ('/cmd_vel_in', '/cmd_vel'),
+        ('/cmd_vel_out', '/cmd_vel_terrain'),
+    ],
+)
+
+terrain_mapper_node = Node(
+    package='saltybot_bringup',
+    executable='terrain_mapper',
+    name='terrain_mapper',
+)
+```
+
+**Update setup.py entry points:**
+```python
+'terrain_classifier = saltybot_bringup.terrain_classifier_node:main'
+'terrain_speed_adapter = saltybot_bringup.terrain_speed_adapter_node:main'
+'terrain_mapper = saltybot_bringup.terrain_mapper_node:main'
+```
+
+### 6. **Integration with Existing Stack**
+- The existing velocity ramp (`velocity_ramp_node.py`) processes `/cmd_vel_smooth` or `/cmd_vel`
+- Optionally, update cmd_vel_bridge to use `/cmd_vel_terrain` if available, else fall back to `/cmd_vel`
+- Terrain classification runs independently at 5 Hz (much slower than velocity ramping at 50 Hz)
+
+### 7. **Future CNN Enhancement**
+The current implementation uses rule-based classification with IMU FFT and camera edge detection. A future enhancement could add a lightweight CNN for texture classification (e.g., MobileNet) by:
+1. Creating a `terrain_classifier_cnn.py` with TensorFlow/ONNX model
+2. Replacing decision logic in `terrain_classifier_node.py` with CNN inference
+3. Maintaining same message interface
+
+## Implementation Tasks
+
+1. ✅ **Phase 1: Message Definition**
+   - Create `TerrainState.msg` in saltybot_social_msgs
+   - Update `CMakeLists.txt`
+
+2. ✅ **Phase 2: Terrain Classifier Node**
+   - Implement `terrain_classifier_node.py` with IMU FFT analysis
+   - Implement camera texture analysis
+   - Decision logic for classification
+
+3. ✅ **Phase 3: Speed Adapter Node**
+   - Implement `terrain_speed_adapter_node.py`
+   - Velocity command adaptation
+
+4. ✅ **Phase 4: Terrain Mapper Node**
+   - Implement `terrain_mapper_node.py` for logging
+
+5. ✅ **Phase 5: Integration**
+   - Update `full_stack.launch.py` with new nodes
+   - Update `setup.py` with entry points
+   - Test integration
+
+## Testing & Verification
+
+**Unit Tests:**
+- Test IMU FFT feature extraction with synthetic vibration data
+- Test terrain classification decision logic
+- Test speed ratio application
+- Test CSV logging format
+
+**Integration Tests:**
+- Run full stack with simulated IMU/camera data
+- Verify terrain messages published at 5 Hz
+- Verify cmd_vel_terrain adapts speeds correctly
+- Check terrain log file is created and properly formatted
+
+**Manual Testing:**
+- Drive robot on different surfaces
+- Verify terrain detection changes appropriately
+- Verify speed adaptation is smooth (no jerks from ramping)
+- Check terrain log CSV has correct format
+
+## Critical Files Summary
+
+**To Create:**
+- `jetson/ros2_ws/src/saltybot_social_msgs/msg/TerrainState.msg`
+- `jetson/ros2_ws/src/saltybot_bringup/saltybot_bringup/terrain_classifier_node.py`
+- `jetson/ros2_ws/src/saltybot_bringup/saltybot_bringup/terrain_speed_adapter_node.py`
+- `jetson/ros2_ws/src/saltybot_bringup/saltybot_bringup/terrain_mapper_node.py`
+
+**To Modify:**
+- `jetson/ros2_ws/src/saltybot_social_msgs/CMakeLists.txt` (add TerrainState.msg)
+- `jetson/ros2_ws/src/saltybot_bringup/launch/full_stack.launch.py` (add nodes)
+- `jetson/ros2_ws/src/saltybot_bringup/setup.py` (add entry points)
+
+**Key Dependencies:**
+- `numpy` — FFT analysis (already available in saltybot)
+- `scipy.signal` — Butterworth filter (optional, for smoothing)
+- `cv2` (OpenCV) — image processing (already available)
+- `tensorflow` or `tf-lite` — MobileNetV2 pre-trained model for texture CNN
+- `rclpy` — ROS2 Python client
+
+**CNN Model Details:**
+- Model: MobileNetV2 pre-trained on ImageNet
+- Input: 224×224 RGB image (downsampled from camera)
+- Output: 1280-dim feature vector from last conv layer before classification
+- Strategy: Use pre-trained features directly (transfer learning) for quick MVP, no fine-tuning needed initially
+- Alternative: Pre-trained weights can be fine-tuned on terrain image dataset in future iterations
+- Inference: ~50-100ms on Jetson Xavier (acceptable at 5 Hz publish rate)
+
+## Terrain Classification Logic (IMU + CNN Fusion)
+
+**Features extracted:**
+1. `imu_roughness` = normalized RMS of high-freq (>10 Hz) accel components (0-1)
+   - Computed from FFT power spectral density in 10-50 Hz band
+   - Reflects mechanical vibration from surface contact
+
+2. `cnn_texture_features` = 1280-dim feature vector from MobileNetV2
+   - Pre-trained features capture texture, edge, and surface characteristics
+   - Reduced to 2-3 principal components via PCA or simple aggregation
+
+3. `accel_magnitude` = RMS of total acceleration (m/s²)
+   - Helps distinguish stationary (9.81 m/s²) vs. moving
+
+**Classification approach (Version 1):**
+- Simple decision tree with IMU-dominant logic + CNN support:
+  ```
+  if imu_roughness < 0.2 and accel_magnitude < 9.8:
+      terrain = PAVEMENT  (confidence boosted if CNN agrees)
+  elif imu_roughness < 0.35 and cnn_grainy_score < 0.4:
+      terrain = GRASS
+  elif imu_roughness > 0.45 and cnn_granular_score > 0.5:
+      terrain = GRAVEL
+  elif cnn_sand_texture_score > 0.6 and imu_roughness > 0.3:
+      terrain = SAND
+  else:
+      terrain = INDOOR
+  ```
+
+- Confidence: weighted combination of IMU and CNN agreement
+- Roughness metric: `0.0 = smooth, 1.0 = very rough` derived from IMU FFT energy ratio
+
+**Speed recommendations:**
+- Pavement: 1.0 (full speed)
+- Grass: 0.8 (20% slower)
+- Gravel: 0.5 (50% slower)
+- Sand: 0.4 (60% slower)
+- Indoor: 0.7 (30% slower by default)
+
+**Future improvement:** Replace decision tree with trained classifier (Random Forest, SVM, or small Dense net) on labeled terrain dataset once collected.
+
+---
+
+This plan follows SaltyBot's established patterns:
+- Pure Python libraries for core logic (_terrain_analysis.py)
+- ROS2 node wrappers for integration
+- Parameter-based configuration in YAML
+- Message-based pub/sub architecture
+- Integration with existing velocity control pipeline

.gitea/workflows/ota-release.yml

@@ -0,0 +1,162 @@
+# .gitea/workflows/ota-release.yml
+# Gitea Actions — ESP32 OTA firmware build & release (bd-9kod)
+#
+# Triggers on signed release tags:
+#   esp32-balance/vX.Y.Z  →  builds esp32s3/balance/   (ESP32-S3 Balance board)
+#   esp32-io/vX.Y.Z       →  builds esp32s3-io/         (ESP32-S3 IO board)
+#
+# Uses the official espressif/idf Docker image for reproducible builds.
+# Attaches <app>_<version>.bin + <app>_<version>.sha256 to the Gitea release.
+# The ESP32 Balance OTA system fetches the .bin from the release asset URL.
+
+name: OTA release — build & attach firmware
+
+on:
+  push:
+    tags:
+      - "esp32-balance/v*"
+      - "esp32-io/v*"
+
+permissions:
+  contents: write
+
+jobs:
+  build-and-release:
+    name: Build ${{ github.ref_name }}
+    runs-on: ubuntu-latest
+    container:
+      image: espressif/idf:v5.2.2
+      options: --user root
+
+    steps:
+      # ── 1. Checkout ───────────────────────────────────────────────────────────
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      # ── 2. Resolve build target from tag ─────────────────────────────────────
+      # Tag format:  esp32-balance/v1.2.3  or  esp32-io/v1.2.3
+      - name: Resolve project from tag
+        id: proj
+        shell: bash
+        run: |
+          TAG="${GITHUB_REF_NAME}"
+          case "$TAG" in
+            esp32-balance/*)
+              DIR="esp32s3/balance"
+              APP="esp32s3_balance"
+              ;;
+            esp32-io/*)
+              DIR="esp32s3-io"
+              APP="esp32s3_io"
+              ;;
+            *)
+              echo "::error::Unrecognised tag prefix: ${TAG}"
+              exit 1
+              ;;
+          esac
+          VERSION="${TAG#*/}"
+          echo "dir=${DIR}"         >> "$GITHUB_OUTPUT"
+          echo "app=${APP}"         >> "$GITHUB_OUTPUT"
+          echo "version=${VERSION}" >> "$GITHUB_OUTPUT"
+          echo "tag=${TAG}"         >> "$GITHUB_OUTPUT"
+          echo "Build: ${APP} ${VERSION} from ${DIR}"
+
+      # ── 3. Build with ESP-IDF ─────────────────────────────────────────────────
+      - name: Build firmware (idf.py build)
+        shell: bash
+        run: |
+          . "${IDF_PATH}/export.sh"
+          cd "${{ steps.proj.outputs.dir }}"
+          idf.py build
+
+      # ── 4. Collect binary & generate checksum ────────────────────────────────
+      - name: Collect artifacts
+        id: art
+        shell: bash
+        run: |
+          APP="${{ steps.proj.outputs.app }}"
+          VER="${{ steps.proj.outputs.version }}"
+          BIN_SRC="${{ steps.proj.outputs.dir }}/build/${APP}.bin"
+          BIN_OUT="${APP}_${VER}.bin"
+          SHA_OUT="${APP}_${VER}.sha256"
+
+          cp "$BIN_SRC" "$BIN_OUT"
+          sha256sum "$BIN_OUT" > "$SHA_OUT"
+
+          echo "bin=${BIN_OUT}" >> "$GITHUB_OUTPUT"
+          echo "sha=${SHA_OUT}" >> "$GITHUB_OUTPUT"
+
+          echo "Binary:   ${BIN_OUT} ($(wc -c < "$BIN_OUT") bytes)"
+          echo "Checksum: $(cat "$SHA_OUT")"
+
+      # ── 5. Archive artifacts in CI workspace ─────────────────────────────────
+      - name: Upload build artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: firmware-${{ steps.proj.outputs.app }}-${{ steps.proj.outputs.version }}
+          path: |
+            ${{ steps.art.outputs.bin }}
+            ${{ steps.art.outputs.sha }}
+
+      # ── 6. Create Gitea release (if needed) & upload assets ──────────────────
+      # Uses GITHUB_TOKEN (auto-provided, contents:write from permissions block).
+      # URL-encodes the tag to handle the slash in esp32-balance/vX.Y.Z.
+      - name: Publish assets to Gitea release
+        shell: bash
+        env:
+          GITEA_URL: https://gitea.vayrette.com
+          TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          REPO: ${{ github.repository }}
+          TAG: ${{ steps.proj.outputs.tag }}
+          BIN: ${{ steps.art.outputs.bin }}
+          SHA: ${{ steps.art.outputs.sha }}
+        run: |
+          API="${GITEA_URL}/api/v1/repos/${REPO}"
+
+          # URL-encode the tag (slash in esp32-balance/vX.Y.Z must be escaped)
+          TAG_ENC=$(python3 -c "
+          import urllib.parse, sys
+          print(urllib.parse.quote(sys.argv[1], safe=''))
+          " "$TAG")
+
+          # Try to fetch an existing release for this tag
+          RELEASE=$(curl -sf \
+            -H "Authorization: token ${TOKEN}" \
+            "${API}/releases/tags/${TAG_ENC}") || true
+
+          # If no release yet, create it
+          if [ -z "$RELEASE" ]; then
+            echo "Creating release for tag: ${TAG}"
+            RELEASE=$(curl -sf \
+              -X POST \
+              -H "Authorization: token ${TOKEN}" \
+              -H "Content-Type: application/json" \
+              -d "$(python3 -c "
+          import json, sys
+          print(json.dumps({
+              'tag_name': sys.argv[1],
+              'name':     sys.argv[1],
+              'draft':    False,
+              'prerelease': False,
+          }))
+          " "$TAG")" \
+              "${API}/releases")
+          fi
+
+          RELEASE_ID=$(echo "$RELEASE" | python3 -c "
+          import sys, json; print(json.load(sys.stdin)['id'])
+          ")
+          echo "Release ID: ${RELEASE_ID}"
+
+          # Upload binary and checksum
+          for FILE in "$BIN" "$SHA"; do
+            FNAME=$(basename "$FILE")
+            echo "Uploading: ${FNAME}"
+            curl -sf \
+              -X POST \
+              -H "Authorization: token ${TOKEN}" \
+              -F "attachment=@${FILE}" \
+              "${API}/releases/${RELEASE_ID}/assets?name=${FNAME}"
+          done
+
+          echo "Published: ${BIN} + ${SHA} → release ${TAG}"

.pio/build/project.checksum

@@ -1 +1 @@
-ee8efb31f6b185f16e4d385971f1a0e3291fe5fd
+ffc01fb580c81760bdda9a672fe1212be4578e3e

AUTONOMOUS_ARMING.md

@@ -0,0 +1,148 @@
+# Autonomous Arming (Issue #512)
+
+## Overview
+The robot can now be armed and operated autonomously from the Jetson without requiring an RC transmitter. The RC receiver (ELRS) is now optional and serves as an override/kill-switch rather than a requirement.
+
+## Arming Sources
+
+### Jetson Autonomous Arming
+- Command: `A\n` (single byte 'A' followed by newline)
+<<<<<<< HEAD
+- Sent via USB CDC to the ESP32 BALANCE firmware
+=======
+- Sent via USB Serial (CH343) to the ESP32-S3 firmware
+>>>>>>> 291dd68 (feat: remove all STM32/Mamba/BlackPill references — ESP32-S3 only)
+- Robot arms after ARMING_HOLD_MS (~500ms) safety hold period
+- Works even when RC is not connected or not armed
+
+### RC Arming (Optional Override)
+- Command: CH5 switch on ELRS transmitter
+- When RC is connected and armed, robot can be armed via RC
+- RC and Jetson can both request arming independently
+
+## Safety Features
+
+### Maintained from Original Design
+1. **Arming Hold Timer** — 500ms hold before motors enable (prevents accidental arming)
+2. **Tilt Safety** — Robot must be within ±10° level to arm
+3. **IMU Calibration** — Gyro must be calibrated before arming
+4. **Remote E-Stop Override** — `safety_remote_estop_active()` blocks all arming
+
+### New for Autonomous Operation
+1. **RC Kill Switch** (CH5 OFF when RC connected)
+   - Triggers emergency stop (motor cutoff) instead of disarm
+   - Allows Jetson-armed robots to remain armed when RC disconnects
+   - Maintains safety of kill switch for emergency situations
+
+2. **RC Failsafe**
+   - If RC signal is lost after being established, robot disarms (500ms timeout)
+   - Prevents runaway if RC connection drops during flight
+   - USB-only mode (no RC ever connected) is unaffected
+
+3. **Jetson Timeout** (200ms heartbeat)
+   - Jetson must send heartbeat (H command) every 500ms
+   - Prevents autonomous runaway if Jetson crashes/loses connection
+   - Handled by `jetson_cmd_is_active()` checks
+
+## Command Protocol
+
+<<<<<<< HEAD
+### From Jetson to ESP32 BALANCE (USB CDC)
+=======
+### From Jetson to ESP32-S3 (USB Serial (CH343))
+>>>>>>> 291dd68 (feat: remove all STM32/Mamba/BlackPill references — ESP32-S3 only)
+```
+A           — Request arm (triggers safety hold, then motors enable)
+D           — Request disarm (immediate motor stop)
+E           — Emergency stop (immediate motor cutoff, latched)
+Z           — Clear emergency stop latch
+H           — Heartbeat (refresh timeout timer, every 500ms)
+C<spd>,<str> — Drive command: speed, steer (also refreshes heartbeat)
+```
+
+<<<<<<< HEAD
+### From ESP32 BALANCE to Jetson (USB CDC)
+=======
+### From ESP32-S3 to Jetson (USB Serial (CH343))
+>>>>>>> 291dd68 (feat: remove all STM32/Mamba/BlackPill references — ESP32-S3 only)
+Motor commands are gated by `bal.state == BALANCE_ARMED`:
+- When ARMED: Motor commands sent every 20ms (50 Hz)
+- When DISARMED: Zero sent every 20ms (prevents ESC timeout)
+
+## Arming State Machine
+
+```
+DISARMED
+  ↓
+  +-- Jetson sends 'A' OR RC CH5 rises (with conditions met)
+      ↓
+      safety_arm_start() called
+      (arm hold timer starts)
+      ↓
+      Wait ARMING_HOLD_MS
+      ↓
+      safety_arm_ready() returns true
+      ↓
+      balance_arm() called
+      ARMED ← (motors now respond to commands)
+
+ARMED
+  ↓
+  +-- Jetson sends 'D' → balance_disarm()
+  +-- RC CH5 falls AND RC still alive → balance_disarm()
+  +-- RC signal lost (failsafe) → balance_disarm()
+  +-- Tilt fault detected → immediate motor stop
+  +-- RC kill switch (CH5 OFF) → emergency stop (not disarm)
+```
+
+## RC Override Priority
+
+When RC is connected and active:
+- **Steer channel**: Blended with Jetson via `mode_manager` (per active mode)
+- **Kill switch**: RC CH5 OFF triggers emergency stop (overrides everything)
+- **Failsafe**: RC signal loss triggers disarm (prevents runaway)
+
+When RC is disconnected:
+- Robot operates under Jetson commands alone
+- Emergency stop remains available via 'E' command from Jetson
+- No automatic mode change; mission continues autonomously
+
+## Testing Checklist
+
+- [ ] Jetson can arm robot without RC (send 'A' command)
+- [ ] Robot motors respond to Jetson drive commands when armed
+- [ ] Robot disarms on Jetson 'D' command
+- [ ] RC kill switch (CH5 OFF) triggers emergency stop without disarming
+- [ ] Robot can be re-armed after RC kill switch via Jetson 'A' command
+- [ ] RC failsafe still works (500ms signal loss = disarm)
+- [ ] Jetson heartbeat timeout works (500ms without H/C = motors zero)
+- [ ] Tilt fault still triggers immediate stop
+- [ ] IMU calibration required before arm
+- [ ] Arming hold timer (500ms) enforced
+
+## Migration from RC-Only
+
+### Old Workflow (ELRS-Required)
+1. Power on robot
+2. Arm via RC CH5
+3. Send speed/steer commands via RC
+4. Disarm via RC CH5
+
+### New Workflow (Autonomous)
+1. Power on robot
+2. Send heartbeat 'H' every 500ms from Jetson
+3. When ready to move, send 'A' command (wait 500ms)
+4. Send drive commands 'C<spd>,<str>' every ≤200ms
+5. When done, send 'D' command to disarm
+
+### New Workflow (RC + Autonomous Mixed)
+1. Power on robot, bring up RC
+2. Jetson sends heartbeat 'H'
+3. Arm via RC CH5 OR Jetson 'A' (both valid)
+4. Control via RC sticks OR Jetson drive commands (blended)
+5. Emergency kill: RC CH5 OFF (emergency stop) OR Jetson 'E'
+6. Disarm: RC CH5 OFF then ON, OR Jetson 'D'
+
+## References
+- Issue #512: Remove ELRS arm requirement
+- Files: `/src/main.c` (arming logic), `/lib/USB_CDC/src/usbd_cdc_if.c` (CDC commands)

CLAUDE.md

@@ -1,17 +1,36 @@
 # SaltyLab Firmware — Agent Playbook
 
 ## Project
-Self-balancing two-wheeled robot: STM32F722 flight controller, hoverboard hub motors, Jetson Nano for AI/SLAM.
+<<<<<<< HEAD
+**SAUL-TEE** — 4-wheel wagon (870×510×550 mm, 23 kg).
+Two ESP32-S3 boards + Jetson Orin via CAN. Full spec: `docs/SAUL-TEE-SYSTEM-REFERENCE.md`
+
+| Board | Role |
+|-------|------|
+| **ESP32-S3 BALANCE** | QMI8658 IMU, PID balance, CAN→VESC (L:68 / R:56), GC9A01 LCD (Waveshare Touch LCD 1.28) |
+| **ESP32-S3 IO** | TBS Crossfire RC, ELRS failover, BTS7960 motors, NFC/baro/ToF, WS2812 |
+| **Jetson Orin** | AI/SLAM, CANable2 USB→CAN, cmds 0x300–0x303, telemetry 0x400–0x401 |
+
+> **Legacy:** `src/` and `include/` = archived STM32 HAL — do not extend. New firmware in `esp32/`.
+=======
+Self-balancing two-wheeled robot: ESP32-S3 ESP32-S3 BALANCE, hoverboard hub motors, Jetson Orin Nano Super for AI/SLAM.
+>>>>>>> 291dd68 (feat: remove all STM32/Mamba/BlackPill references — ESP32-S3 only)
 
 ## Team
 | Agent | Role | Focus |
 |-------|------|-------|
-| **sl-firmware** | Embedded Firmware Lead | STM32 HAL, USB CDC debugging, SPI/UART, PlatformIO, DFU bootloader |
+<<<<<<< HEAD
+| **sl-firmware** | Embedded Firmware Lead | ESP32-S3, ESP-IDF, QMI8658, CAN/UART protocol, BTS7960 |
+| **sl-controls** | Control Systems Engineer | PID tuning, IMU fusion, balance loop, safety |
+| **sl-perception** | Perception / SLAM Engineer | Jetson Orin, RealSense D435i, RPLIDAR, ROS2, Nav2 |
+=======
+| **sl-firmware** | Embedded Firmware Lead | ESP-IDF, USB Serial (CH343) debugging, SPI/UART, PlatformIO, DFU bootloader |
 | **sl-controls** | Control Systems Engineer | PID tuning, IMU sensor fusion, real-time control loops, safety systems |
-| **sl-perception** | Perception / SLAM Engineer | Jetson Nano, RealSense D435i, RPLIDAR, ROS2, Nav2 |
+| **sl-perception** | Perception / SLAM Engineer | Jetson Orin Nano Super, RealSense D435i, RPLIDAR, ROS2, Nav2 |
+>>>>>>> 291dd68 (feat: remove all STM32/Mamba/BlackPill references — ESP32-S3 only)
 
 ## Status
-USB CDC TX bug resolved (PR #10 — DCache MPU non-cacheable region + IWDG ordering fix).
+USB Serial (CH343) TX bug resolved (PR #10 — DCache MPU non-cacheable region + IWDG ordering fix).
 
 ## Repo Structure
 - `projects/saltybot/SALTYLAB.md` — Design doc
@@ -29,11 +48,11 @@ USB CDC TX bug resolved (PR #10 — DCache MPU non-cacheable region + IWDG order
 | `saltyrover-dev` | Integration — rover variant |
 | `saltytank` | Stable — tracked tank variant |
 | `saltytank-dev` | Integration — tank variant |
-| `main` | Shared code only (IMU drivers, USB CDC, balance core, safety) |
+| `main` | Shared code only (IMU drivers, USB Serial (CH343), balance core, safety) |
 
 ### Rules
 - Agents branch FROM `<variant>-dev` and PR back TO `<variant>-dev`
-- Shared/infrastructure code (IMU drivers, USB CDC, balance core, safety) goes in `main`
+- Shared/infrastructure code (IMU drivers, USB Serial (CH343), balance core, safety) goes in `main`
 - Variant-specific code (motor topology, kinematics, config) goes in variant branches
 - Stable branches get promoted from `-dev` after review and hardware testing
 - **Current SaltyLab team** works against `saltylab-dev`

TEAM.md

@@ -1,12 +1,22 @@
 # SaltyLab — Ideal Team
 
 ## Project
-Self-balancing two-wheeled robot using a drone flight controller (STM32F722), hoverboard hub motors, and eventually a Jetson Nano for AI/SLAM.
+<<<<<<< HEAD
+**SAUL-TEE** — 4-wheel wagon (870×510×550 mm, 23 kg).
+Two ESP32-S3 boards (BALANCE + IO) + Jetson Orin. See `docs/SAUL-TEE-SYSTEM-REFERENCE.md`.
+
+## Current Status
+- **Hardware:** ESP32-S3 BALANCE (Waveshare Touch LCD 1.28, CH343 USB) + ESP32-S3 IO (bare devkit, JTAG USB)
+- **Firmware:** ESP-IDF/PlatformIO target; legacy `src/` STM32 HAL archived
+- **Comms:** UART 460800 baud inter-board; CANable2 USB→CAN for Orin; CAN 500 kbps to VESCs (L:68 / R:56)
+=======
+Self-balancing two-wheeled robot using a drone ESP32-S3 BALANCE (ESP32-S3), hoverboard hub motors, and eventually a Jetson Orin Nano Super for AI/SLAM.
 
 ## Current Status
 - **Hardware:** Assembled — FC, motors, ESC, IMU, battery, RC all on hand
-- **Firmware:** Balance PID + hoverboard ESC protocol written, but blocked by USB CDC bug
-- **Blocker:** USB CDC TX stops working when peripheral inits (SPI/UART/GPIO) are added alongside USB OTG FS — see `USB_CDC_BUG.md`
+- **Firmware:** Balance PID + hoverboard ESC protocol written, but blocked by USB Serial (CH343) bug
+- **Blocker:** USB Serial (CH343) TX stops working when peripheral inits (SPI/UART/GPIO) are added alongside USB on ESP32-S3 — see `legacy/stm32/USB_CDC_BUG.md` for historical context
+>>>>>>> 291dd68 (feat: remove all STM32/Mamba/BlackPill references — ESP32-S3 only)
 
 ---
 
@@ -14,18 +24,30 @@ Self-balancing two-wheeled robot using a drone flight controller (STM32F722), ho
 
 ### 1. Embedded Firmware Engineer (Lead)
 **Must-have:**
-- Deep STM32 HAL experience (F7 series specifically)
+<<<<<<< HEAD
+- Deep ESP32 (Arduino/ESP-IDF) or STM32 HAL experience
 - USB OTG FS / CDC ACM debugging (TxState, endpoint management, DMA conflicts)
-- SPI + UART + USB coexistence on STM32
-- PlatformIO or bare-metal STM32 toolchain
+- SPI + UART + USB coexistence on ESP32
+- PlatformIO or bare-metal ESP32 toolchain
 - DFU bootloader implementation
+=======
+- Deep ESP-IDF experience (ESP32-S3 specifically)
+- USB Serial (CH343) / UART debugging on ESP32-S3
+- SPI + UART + USB coexistence on ESP32-S3
+- ESP-IDF / Arduino-ESP32 toolchain
+- OTA firmware update implementation
+>>>>>>> 291dd68 (feat: remove all STM32/Mamba/BlackPill references — ESP32-S3 only)
 
 **Nice-to-have:**
-- Betaflight/iNav/ArduPilot codebase familiarity
+- ESP32-S3 peripheral coexistence (SPI + UART + USB)
 - PID control loop tuning for balance robots
 - FOC motor control (hoverboard ESC protocol)
 
-**Why:** The immediate blocker is a USB peripheral conflict. Need someone who's debugged STM32 USB issues before — this is not a software logic bug, it's a hardware peripheral interaction issue.
+<<<<<<< HEAD
+**Why:** The immediate blocker is a USB peripheral conflict. Need someone who's debugged STM32 USB issues before — ESP32 firmware for the balance loop and I/O needs to be written from scratch.
+=======
+**Why:** The immediate blocker is a USB peripheral conflict on ESP32-S3. Need someone who's debugged ESP32-S3 USB Serial (CH343) issues before — this is not a software logic bug, it's a hardware peripheral interaction issue.
+>>>>>>> 291dd68 (feat: remove all STM32/Mamba/BlackPill references — ESP32-S3 only)
 
 ### 2. Control Systems / Robotics Engineer
 **Must-have:**
@@ -43,7 +65,7 @@ Self-balancing two-wheeled robot using a drone flight controller (STM32F722), ho
 
 ### 3. Perception / SLAM Engineer (Phase 2)
 **Must-have:**
-- Jetson Nano / NVIDIA Jetson platform
+- Jetson Orin Nano Super / NVIDIA Jetson platform
 - Intel RealSense D435i depth camera
 - RPLIDAR integration
 - SLAM (ORB-SLAM3, RTAB-Map, or similar)
@@ -54,19 +76,23 @@ Self-balancing two-wheeled robot using a drone flight controller (STM32F722), ho
 - Obstacle avoidance
 - Nav2 stack
 
-**Why:** Phase 2 goal is autonomous navigation. Jetson Nano with RealSense + RPLIDAR for indoor mapping and person following.
+**Why:** Phase 2 goal is autonomous navigation. Jetson Orin Nano Super with RealSense + RPLIDAR for indoor mapping and person following.
 
 ---
 
 ## Hardware Reference
 | Component | Details |
 |-----------|---------|
-| FC | MAMBA F722S (STM32F722RET6, MPU6000) |
+<<<<<<< HEAD
+| FC | ESP32 BALANCE (ESP32RET6, MPU6000) |
+=======
+| FC | ESP32-S3 BALANCE (ESP32-S3RET6, QMI8658) |
+>>>>>>> 291dd68 (feat: remove all STM32/Mamba/BlackPill references — ESP32-S3 only)
 | Motors | 2x 8" pneumatic hoverboard hub motors |
 | ESC | Hoverboard ESC (EFeru FOC firmware) |
 | Battery | 36V pack |
 | RC | BetaFPV ELRS 2.4GHz TX + RX |
-| AI Brain | Jetson Nano + Noctua fan |
+| AI Brain | Jetson Orin Nano Super + Noctua fan |
 | Depth | Intel RealSense D435i |
 | LIDAR | RPLIDAR A1M8 |
 | Spare IMUs | BNO055, MPU6050 |
@@ -74,4 +100,4 @@ Self-balancing two-wheeled robot using a drone flight controller (STM32F722), ho
 ## Repo
 - Gitea: https://gitea.vayrette.com/seb/saltylab-firmware
 - Design doc: `projects/saltybot/SALTYLAB.md`
-- Bug doc: `USB_CDC_BUG.md`
+- Bug doc: `legacy/stm32/USB_CDC_BUG.md` (archived — STM32 era)

USB_CDC_BUG.md

@@ -1,44 +0,0 @@
-# USB CDC TX Bug — 2026-02-28
-
-## Problem
-Balance firmware produces no USB CDC output. Minimal "hello" test firmware works fine.
-
-## What Works
-- **Test firmware** (just sends `{"hello":N}` at 10Hz after 3s delay): **DATA FLOWS**
-- USB enumeration works in both cases (port appears as `/dev/cu.usbmodemSALTY0011`)
-- DFU reboot via RTC backup register works (Betaflight-proven pattern)
-
-## What Doesn't Work
-- **Balance firmware**: port opens, no data ever arrives
-- Tried: removing init transmit, 3s boot delay, TxState recovery, DTR detection, streaming flags
-- None of it helps
-
-## Key Difference Between Working & Broken
-- **Working test**: main.c only includes USB CDC headers, HAL, string, stdio
-- **Balance firmware**: includes icm42688.h, bmp280.h, balance.h, hoverboard.h, config.h, status.h
-- Balance firmware inits SPI1 (IMU), USART2 (hoverboard), GPIO (LEDs, buzzer)
-- Likely culprit: **peripheral init (SPI/UART/GPIO) is interfering with USB OTG FS**
-
-## Suspected Root Cause
-One of the additional peripheral inits (SPI1 for IMU, USART2 for hoverboard ESC, or GPIO for status LEDs) is likely conflicting with the USB OTG FS peripheral — either a clock conflict, GPIO pin conflict, or interrupt priority issue.
-
-## Hardware
-- MAMBA F722S FC (STM32F722RET6)
-- Betaflight target: DIAT-MAMBAF722_2022B
-- IMU: MPU6000 on SPI1 (PA4/PA5/PA6/PA7)
-- USB: OTG FS (PA11/PA12)
-- Hoverboard ESC: USART2 (PA2/PA3)
-- LEDs: PC14, PC15
-- Buzzer: PB2
-
-## Files
-- PlatformIO project: `~/Projects/saltylab-firmware/` on mbpm4 (192.168.87.40)
-- Working test: was in src/main.c (replaced with balance code)
-- Balance main.c backup: src/main.c.bak
-- CDC implementation: lib/USB_CDC/src/usbd_cdc_if.c
-
-## To Debug
-1. Add peripherals one at a time to the test firmware to find which one breaks CDC TX
-2. Check for GPIO pin conflicts with USB OTG FS (PA11/PA12)
-3. Check interrupt priorities — USB OTG FS IRQ might be getting starved
-4. Check if DCache (disabled via SCB_DisableDCache) is needed for USB DMA

android/build.gradle

@@ -0,0 +1,46 @@
+plugins {
+    id 'com.android.application'
+    id 'kotlin-android'
+}
+
+android {
+    compileSdk 34
+    namespace 'com.saltylab.uwbtag'
+
+    defaultConfig {
+        applicationId "com.saltylab.uwbtag"
+        minSdk 26
+        targetSdk 34
+        versionCode 1
+        versionName "1.0"
+    }
+
+    buildTypes {
+        release {
+            minifyEnabled false
+        }
+    }
+
+    buildFeatures {
+        viewBinding true
+    }
+
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_17
+        targetCompatibility JavaVersion.VERSION_17
+    }
+
+    kotlinOptions {
+        jvmTarget = '17'
+    }
+}
+
+dependencies {
+    implementation 'androidx.core:core-ktx:1.12.0'
+    implementation 'androidx.appcompat:appcompat:1.6.1'
+    implementation 'com.google.android.material:material:1.11.0'
+    implementation 'androidx.recyclerview:recyclerview:1.3.2'
+    implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.7.0'
+    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3'
+    implementation 'com.google.code.gson:gson:2.10.1'
+}

android/src/main/AndroidManifest.xml

@@ -0,0 +1,37 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <!-- BLE permissions (API 31+) -->
+    <uses-permission android:name="android.permission.BLUETOOTH_SCAN"
+        android:usesPermissionFlags="neverForLocation" />
+    <uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
+    <uses-permission android:name="android.permission.BLUETOOTH_ADVERTISE" />
+
+    <!-- Legacy BLE (API < 31) -->
+    <uses-permission android:name="android.permission.BLUETOOTH"
+        android:maxSdkVersion="30" />
+    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"
+        android:maxSdkVersion="30" />
+    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"
+        android:maxSdkVersion="30" />
+
+    <uses-feature android:name="android.hardware.bluetooth_le" android:required="true" />
+
+    <application
+        android:allowBackup="true"
+        android:label="UWB Tag Config"
+        android:theme="@style/Theme.MaterialComponents.DayNight.DarkActionBar">
+
+        <activity
+            android:name=".UwbTagBleActivity"
+            android:exported="true"
+            android:launchMode="singleTop">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+
+    </application>
+
+</manifest>

android/src/main/kotlin/com/saltylab/uwbtag/UwbTagBleActivity.kt

@@ -0,0 +1,444 @@
+package com.saltylab.uwbtag
+
+import android.Manifest
+import android.annotation.SuppressLint
+import android.bluetooth.*
+import android.bluetooth.le.*
+import android.content.Context
+import android.content.pm.PackageManager
+import android.os.Build
+import android.os.Bundle
+import android.os.Handler
+import android.os.Looper
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.Button
+import android.widget.TextView
+import android.widget.Toast
+import androidx.appcompat.app.AppCompatActivity
+import androidx.core.app.ActivityCompat
+import androidx.core.content.ContextCompat
+import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.RecyclerView
+import com.google.android.material.card.MaterialCardView
+import com.google.android.material.switchmaterial.SwitchMaterial
+import com.google.android.material.textfield.TextInputEditText
+import com.google.gson.Gson
+import com.saltylab.uwbtag.databinding.ActivityUwbTagBleBinding
+import java.util.UUID
+
+// ---------------------------------------------------------------------------
+// GATT service / characteristic UUIDs
+// ---------------------------------------------------------------------------
+private val SERVICE_UUID     = UUID.fromString("12345678-1234-5678-1234-56789abcdef0")
+private val CHAR_CONFIG_UUID = UUID.fromString("12345678-1234-5678-1234-56789abcdef1") // read/write JSON config
+private val CHAR_STATUS_UUID = UUID.fromString("12345678-1234-5678-1234-56789abcdef2") // notify: tag status string
+private val CHAR_BATT_UUID   = UUID.fromString("12345678-1234-5678-1234-56789abcdef3") // notify: battery %
+private val CCCD_UUID        = UUID.fromString("00002902-0000-1000-8000-00805f9b34fb")
+
+// BLE scan timeout
+private const val SCAN_TIMEOUT_MS = 15_000L
+
+// Permissions request code
+private const val REQ_PERMISSIONS = 1001
+
+// ---------------------------------------------------------------------------
+// Data model
+// ---------------------------------------------------------------------------
+data class TagConfig(
+    val tag_name: String = "UWB_TAG_0001",
+    val sleep_timeout_s: Int = 300,
+    val display_brightness: Int = 50,
+    val uwb_channel: Int = 9,
+    val ranging_interval_ms: Int = 100,
+    val battery_report: Boolean = true
+)
+
+data class ScannedDevice(
+    val name: String,
+    val address: String,
+    var rssi: Int,
+    val device: BluetoothDevice
+)
+
+// ---------------------------------------------------------------------------
+// RecyclerView adapter for scanned devices
+// ---------------------------------------------------------------------------
+class DeviceAdapter(
+    private val onConnect: (ScannedDevice) -> Unit
+) : RecyclerView.Adapter<DeviceAdapter.VH>() {
+
+    private val items = mutableListOf<ScannedDevice>()
+
+    fun update(device: ScannedDevice) {
+        val idx = items.indexOfFirst { it.address == device.address }
+        if (idx >= 0) {
+            items[idx] = device
+            notifyItemChanged(idx)
+        } else {
+            items.add(device)
+            notifyItemInserted(items.size - 1)
+        }
+    }
+
+    fun clear() {
+        items.clear()
+        notifyDataSetChanged()
+    }
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): VH {
+        val view = LayoutInflater.from(parent.context)
+            .inflate(R.layout.item_ble_device, parent, false)
+        return VH(view)
+    }
+
+    override fun onBindViewHolder(holder: VH, position: Int) = holder.bind(items[position])
+    override fun getItemCount() = items.size
+
+    inner class VH(view: View) : RecyclerView.ViewHolder(view) {
+        private val tvName    = view.findViewById<TextView>(R.id.tvDeviceName)
+        private val tvAddress = view.findViewById<TextView>(R.id.tvDeviceAddress)
+        private val tvRssi    = view.findViewById<TextView>(R.id.tvRssi)
+        private val btnConn   = view.findViewById<Button>(R.id.btnConnect)
+
+        fun bind(item: ScannedDevice) {
+            tvName.text    = item.name
+            tvAddress.text = item.address
+            tvRssi.text    = "${item.rssi} dBm"
+            btnConn.setOnClickListener { onConnect(item) }
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Activity
+// ---------------------------------------------------------------------------
+@SuppressLint("MissingPermission") // permissions checked at runtime before any BLE call
+class UwbTagBleActivity : AppCompatActivity() {
+
+    private lateinit var binding: ActivityUwbTagBleBinding
+    private val gson = Gson()
+    private val mainHandler = Handler(Looper.getMainLooper())
+
+    // BLE
+    private val btManager by lazy { getSystemService(Context.BLUETOOTH_SERVICE) as BluetoothManager }
+    private val btAdapter by lazy { btManager.adapter }
+    private var bleScanner: BluetoothLeScanner? = null
+    private var gatt: BluetoothGatt? = null
+    private var configChar: BluetoothGattCharacteristic? = null
+    private var statusChar: BluetoothGattCharacteristic? = null
+    private var battChar: BluetoothGattCharacteristic? = null
+    private var isScanning = false
+
+    private val deviceAdapter = DeviceAdapter(onConnect = ::connectToDevice)
+
+    // ---------------------------------------------------------------------------
+    // Lifecycle
+    // ---------------------------------------------------------------------------
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        binding = ActivityUwbTagBleBinding.inflate(layoutInflater)
+        setContentView(binding.root)
+        setSupportActionBar(binding.toolbar)
+
+        binding.rvDevices.layoutManager = LinearLayoutManager(this)
+        binding.rvDevices.adapter = deviceAdapter
+
+        binding.btnScan.setOnClickListener {
+            if (isScanning) stopScan() else startScanIfPermitted()
+        }
+        binding.btnDisconnect.setOnClickListener { disconnectGatt() }
+        binding.btnReadConfig.setOnClickListener { readConfig() }
+        binding.btnWriteConfig.setOnClickListener { writeConfig() }
+
+        requestBlePermissions()
+    }
+
+    override fun onDestroy() {
+        super.onDestroy()
+        stopScan()
+        disconnectGatt()
+    }
+
+    // ---------------------------------------------------------------------------
+    // Permissions
+    // ---------------------------------------------------------------------------
+    private fun requestBlePermissions() {
+        val needed = mutableListOf<String>()
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
+            if (!hasPermission(Manifest.permission.BLUETOOTH_SCAN))
+                needed += Manifest.permission.BLUETOOTH_SCAN
+            if (!hasPermission(Manifest.permission.BLUETOOTH_CONNECT))
+                needed += Manifest.permission.BLUETOOTH_CONNECT
+        } else {
+            if (!hasPermission(Manifest.permission.ACCESS_FINE_LOCATION))
+                needed += Manifest.permission.ACCESS_FINE_LOCATION
+        }
+        if (needed.isNotEmpty()) {
+            ActivityCompat.requestPermissions(this, needed.toTypedArray(), REQ_PERMISSIONS)
+        }
+    }
+
+    private fun hasPermission(perm: String) =
+        ContextCompat.checkSelfPermission(this, perm) == PackageManager.PERMISSION_GRANTED
+
+    override fun onRequestPermissionsResult(
+        requestCode: Int, permissions: Array<out String>, grantResults: IntArray
+    ) {
+        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
+        if (requestCode == REQ_PERMISSIONS &&
+            grantResults.any { it != PackageManager.PERMISSION_GRANTED }) {
+            toast("BLE permissions required")
+        }
+    }
+
+    // ---------------------------------------------------------------------------
+    // BLE Scan
+    // ---------------------------------------------------------------------------
+    private fun startScanIfPermitted() {
+        if (btAdapter?.isEnabled != true) { toast("Bluetooth is off"); return }
+        bleScanner = btAdapter.bluetoothLeScanner
+        val filter = ScanFilter.Builder()
+            .setDeviceNamePattern("UWB_TAG_.*".toRegex().toPattern())
+            .build()
+        val settings = ScanSettings.Builder()
+            .setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY)
+            .build()
+        deviceAdapter.clear()
+        bleScanner?.startScan(listOf(filter), settings, scanCallback)
+        isScanning = true
+        binding.btnScan.text = "Stop"
+        binding.tvScanStatus.text = "Scanning…"
+        mainHandler.postDelayed({ stopScan() }, SCAN_TIMEOUT_MS)
+    }
+
+    private fun stopScan() {
+        bleScanner?.stopScan(scanCallback)
+        isScanning = false
+        binding.btnScan.text = "Scan"
+        binding.tvScanStatus.text = "Scan stopped"
+    }
+
+    private val scanCallback = object : ScanCallback() {
+        override fun onScanResult(callbackType: Int, result: ScanResult) {
+            val name = result.device.name ?: return
+            if (!name.startsWith("UWB_TAG_")) return
+            val dev = ScannedDevice(
+                name    = name,
+                address = result.device.address,
+                rssi    = result.rssi,
+                device  = result.device
+            )
+            mainHandler.post { deviceAdapter.update(dev) }
+        }
+
+        override fun onScanFailed(errorCode: Int) {
+            mainHandler.post {
+                binding.tvScanStatus.text = "Scan failed (code $errorCode)"
+                isScanning = false
+                binding.btnScan.text = "Scan"
+            }
+        }
+    }
+
+    // ---------------------------------------------------------------------------
+    // GATT Connection
+    // ---------------------------------------------------------------------------
+    private fun connectToDevice(scanned: ScannedDevice) {
+        stopScan()
+        binding.tvScanStatus.text = "Connecting to ${scanned.name}…"
+        gatt = scanned.device.connectGatt(this, false, gattCallback, BluetoothDevice.TRANSPORT_LE)
+    }
+
+    private fun disconnectGatt() {
+        gatt?.disconnect()
+        gatt?.close()
+        gatt = null
+        configChar = null
+        statusChar = null
+        battChar = null
+        mainHandler.post {
+            binding.cardConfig.visibility = View.GONE
+            binding.tvScanStatus.text = "Disconnected"
+        }
+    }
+
+    private val gattCallback = object : BluetoothGattCallback() {
+
+        override fun onConnectionStateChange(g: BluetoothGatt, status: Int, newState: Int) {
+            when (newState) {
+                BluetoothProfile.STATE_CONNECTED -> {
+                    mainHandler.post { binding.tvScanStatus.text = "Connected — discovering services…" }
+                    g.discoverServices()
+                }
+                BluetoothProfile.STATE_DISCONNECTED -> {
+                    mainHandler.post {
+                        binding.cardConfig.visibility = View.GONE
+                        binding.tvScanStatus.text = "Disconnected"
+                        toast("Tag disconnected")
+                    }
+                    gatt?.close()
+                    gatt = null
+                }
+            }
+        }
+
+        override fun onServicesDiscovered(g: BluetoothGatt, status: Int) {
+            if (status != BluetoothGatt.GATT_SUCCESS) {
+                mainHandler.post { toast("Service discovery failed") }
+                return
+            }
+            val service = g.getService(SERVICE_UUID)
+            if (service == null) {
+                mainHandler.post { toast("UWB config service not found on tag") }
+                return
+            }
+            configChar = service.getCharacteristic(CHAR_CONFIG_UUID)
+            statusChar = service.getCharacteristic(CHAR_STATUS_UUID)
+            battChar   = service.getCharacteristic(CHAR_BATT_UUID)
+
+            // Subscribe to status notifications
+            statusChar?.let { enableNotifications(g, it) }
+            battChar?.let   { enableNotifications(g, it) }
+
+            // Initial config read
+            configChar?.let { g.readCharacteristic(it) }
+
+            mainHandler.post {
+                val devName = g.device.name ?: g.device.address
+                binding.tvConnectedName.text = "Connected: $devName"
+                binding.cardConfig.visibility = View.VISIBLE
+                binding.tvScanStatus.text = "Connected to $devName"
+            }
+        }
+
+        override fun onCharacteristicRead(
+            g: BluetoothGatt,
+            characteristic: BluetoothGattCharacteristic,
+            status: Int
+        ) {
+            if (status != BluetoothGatt.GATT_SUCCESS) return
+            if (characteristic.uuid == CHAR_CONFIG_UUID) {
+                val json = characteristic.value?.toString(Charsets.UTF_8) ?: return
+                val cfg = runCatching { gson.fromJson(json, TagConfig::class.java) }.getOrNull() ?: return
+                mainHandler.post { populateFields(cfg) }
+            }
+        }
+
+        // API 33+ callback
+        override fun onCharacteristicRead(
+            g: BluetoothGatt,
+            characteristic: BluetoothGattCharacteristic,
+            value: ByteArray,
+            status: Int
+        ) {
+            if (status != BluetoothGatt.GATT_SUCCESS) return
+            if (characteristic.uuid == CHAR_CONFIG_UUID) {
+                val json = value.toString(Charsets.UTF_8)
+                val cfg = runCatching { gson.fromJson(json, TagConfig::class.java) }.getOrNull() ?: return
+                mainHandler.post { populateFields(cfg) }
+            }
+        }
+
+        override fun onCharacteristicWrite(
+            g: BluetoothGatt,
+            characteristic: BluetoothGattCharacteristic,
+            status: Int
+        ) {
+            val msg = if (status == BluetoothGatt.GATT_SUCCESS) "Config written" else "Write failed ($status)"
+            mainHandler.post { toast(msg) }
+        }
+
+        override fun onCharacteristicChanged(
+            g: BluetoothGatt,
+            characteristic: BluetoothGattCharacteristic
+        ) {
+            val value = characteristic.value ?: return
+            handleNotification(characteristic.uuid, value)
+        }
+
+        // API 33+ callback
+        override fun onCharacteristicChanged(
+            g: BluetoothGatt,
+            characteristic: BluetoothGattCharacteristic,
+            value: ByteArray
+        ) {
+            handleNotification(characteristic.uuid, value)
+        }
+    }
+
+    // ---------------------------------------------------------------------------
+    // Notification helpers
+    // ---------------------------------------------------------------------------
+    private fun enableNotifications(g: BluetoothGatt, char: BluetoothGattCharacteristic) {
+        g.setCharacteristicNotification(char, true)
+        val descriptor = char.getDescriptor(CCCD_UUID) ?: return
+        descriptor.value = BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE
+        g.writeDescriptor(descriptor)
+    }
+
+    private fun handleNotification(uuid: UUID, value: ByteArray) {
+        val text = value.toString(Charsets.UTF_8)
+        mainHandler.post {
+            when (uuid) {
+                CHAR_STATUS_UUID -> binding.tvTagStatus.text = "Status: $text"
+                CHAR_BATT_UUID   -> {
+                    val pct = text.toIntOrNull() ?: return@post
+                    binding.tvTagStatus.text = binding.tvTagStatus.text.toString()
+                        .replace(Regex("\\| Batt:.*"), "")
+                        .trimEnd() + " | Batt: $pct%"
+                }
+            }
+        }
+    }
+
+    // ---------------------------------------------------------------------------
+    // Config read / write
+    // ---------------------------------------------------------------------------
+    private fun readConfig() {
+        val g = gatt ?: run { toast("Not connected"); return }
+        val c = configChar ?: run { toast("Config char not found"); return }
+        g.readCharacteristic(c)
+    }
+
+    private fun writeConfig() {
+        val g = gatt ?: run { toast("Not connected"); return }
+        val c = configChar ?: run { toast("Config char not found"); return }
+        val cfg = buildConfigFromFields()
+        val json = gson.toJson(cfg)
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+            g.writeCharacteristic(c, json.toByteArray(Charsets.UTF_8),
+                BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT)
+        } else {
+            @Suppress("DEPRECATION")
+            c.value = json.toByteArray(Charsets.UTF_8)
+            @Suppress("DEPRECATION")
+            g.writeCharacteristic(c)
+        }
+    }
+
+    // ---------------------------------------------------------------------------
+    // UI helpers
+    // ---------------------------------------------------------------------------
+    private fun populateFields(cfg: TagConfig) {
+        binding.etTagName.setText(cfg.tag_name)
+        binding.etSleepTimeout.setText(cfg.sleep_timeout_s.toString())
+        binding.etBrightness.setText(cfg.display_brightness.toString())
+        binding.etUwbChannel.setText(cfg.uwb_channel.toString())
+        binding.etRangingInterval.setText(cfg.ranging_interval_ms.toString())
+        binding.switchBatteryReport.isChecked = cfg.battery_report
+    }
+
+    private fun buildConfigFromFields() = TagConfig(
+        tag_name           = binding.etTagName.text?.toString() ?: "UWB_TAG_0001",
+        sleep_timeout_s    = binding.etSleepTimeout.text?.toString()?.toIntOrNull() ?: 300,
+        display_brightness = binding.etBrightness.text?.toString()?.toIntOrNull() ?: 50,
+        uwb_channel        = binding.etUwbChannel.text?.toString()?.toIntOrNull() ?: 9,
+        ranging_interval_ms = binding.etRangingInterval.text?.toString()?.toIntOrNull() ?: 100,
+        battery_report     = binding.switchBatteryReport.isChecked
+    )
+
+    private fun toast(msg: String) =
+        Toast.makeText(this, msg, Toast.LENGTH_SHORT).show()
+}

android/src/main/res/layout/activity_uwb_tag_ble.xml

@@ -0,0 +1,238 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical">
+
+    <androidx.appcompat.widget.Toolbar
+        android:id="@+id/toolbar"
+        android:layout_width="match_parent"
+        android:layout_height="?attr/actionBarSize"
+        android:background="?attr/colorPrimary"
+        android:elevation="4dp"
+        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
+        app:title="UWB Tag BLE Config" />
+
+    <!-- Scan controls -->
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="horizontal"
+        android:padding="12dp"
+        android:gravity="center_vertical">
+
+        <Button
+            android:id="@+id/btnScan"
+            style="@style/Widget.MaterialComponents.Button"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="Scan" />
+
+        <TextView
+            android:id="@+id/tvScanStatus"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_weight="1"
+            android:layout_marginStart="12dp"
+            android:text="Tap Scan to find UWB tags"
+            android:textAppearance="@style/TextAppearance.MaterialComponents.Body2" />
+
+    </LinearLayout>
+
+    <!-- Scan results list -->
+    <TextView
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:paddingHorizontal="12dp"
+        android:text="Nearby Tags"
+        android:textAppearance="@style/TextAppearance.MaterialComponents.Subtitle1"
+        android:textStyle="bold" />
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/rvDevices"
+        android:layout_width="match_parent"
+        android:layout_height="0dp"
+        android:layout_weight="1"
+        android:padding="8dp"
+        android:clipToPadding="false" />
+
+    <!-- Connected device config panel -->
+    <com.google.android.material.card.MaterialCardView
+        android:id="@+id/cardConfig"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_margin="8dp"
+        android:visibility="gone"
+        app:cardElevation="4dp">
+
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:orientation="vertical"
+            android:padding="12dp">
+
+            <LinearLayout
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:orientation="horizontal"
+                android:gravity="center_vertical">
+
+                <TextView
+                    android:id="@+id/tvConnectedName"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_weight="1"
+                    android:text="Connected: —"
+                    android:textAppearance="@style/TextAppearance.MaterialComponents.Subtitle1"
+                    android:textStyle="bold" />
+
+                <Button
+                    android:id="@+id/btnDisconnect"
+                    style="@style/Widget.MaterialComponents.Button.OutlinedButton"
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:text="Disconnect" />
+
+            </LinearLayout>
+
+            <!-- tag_name -->
+            <com.google.android.material.textfield.TextInputLayout
+                style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox.Dense"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="8dp"
+                android:hint="Tag Name">
+                <com.google.android.material.textfield.TextInputEditText
+                    android:id="@+id/etTagName"
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:inputType="text" />
+            </com.google.android.material.textfield.TextInputLayout>
+
+            <!-- sleep_timeout_s and uwb_channel (row) -->
+            <LinearLayout
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:orientation="horizontal"
+                android:layout_marginTop="4dp">
+
+                <com.google.android.material.textfield.TextInputLayout
+                    style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox.Dense"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_weight="1"
+                    android:layout_marginEnd="4dp"
+                    android:hint="Sleep Timeout (s)">
+                    <com.google.android.material.textfield.TextInputEditText
+                        android:id="@+id/etSleepTimeout"
+                        android:layout_width="match_parent"
+                        android:layout_height="wrap_content"
+                        android:inputType="number" />
+                </com.google.android.material.textfield.TextInputLayout>
+
+                <com.google.android.material.textfield.TextInputLayout
+                    style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox.Dense"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_weight="1"
+                    android:layout_marginStart="4dp"
+                    android:hint="UWB Channel">
+                    <com.google.android.material.textfield.TextInputEditText
+                        android:id="@+id/etUwbChannel"
+                        android:layout_width="match_parent"
+                        android:layout_height="wrap_content"
+                        android:inputType="number" />
+                </com.google.android.material.textfield.TextInputLayout>
+
+            </LinearLayout>
+
+            <!-- display_brightness and ranging_interval_ms (row) -->
+            <LinearLayout
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:orientation="horizontal"
+                android:layout_marginTop="4dp">
+
+                <com.google.android.material.textfield.TextInputLayout
+                    style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox.Dense"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_weight="1"
+                    android:layout_marginEnd="4dp"
+                    android:hint="Brightness (0-100)">
+                    <com.google.android.material.textfield.TextInputEditText
+                        android:id="@+id/etBrightness"
+                        android:layout_width="match_parent"
+                        android:layout_height="wrap_content"
+                        android:inputType="number" />
+                </com.google.android.material.textfield.TextInputLayout>
+
+                <com.google.android.material.textfield.TextInputLayout
+                    style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox.Dense"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_weight="1"
+                    android:layout_marginStart="4dp"
+                    android:hint="Ranging Interval (ms)">
+                    <com.google.android.material.textfield.TextInputEditText
+                        android:id="@+id/etRangingInterval"
+                        android:layout_width="match_parent"
+                        android:layout_height="wrap_content"
+                        android:inputType="number" />
+                </com.google.android.material.textfield.TextInputLayout>
+
+            </LinearLayout>
+
+            <!-- battery_report toggle -->
+            <com.google.android.material.switchmaterial.SwitchMaterial
+                android:id="@+id/switchBatteryReport"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="8dp"
+                android:text="Battery Reporting" />
+
+            <!-- Action buttons -->
+            <LinearLayout
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:orientation="horizontal"
+                android:layout_marginTop="8dp">
+
+                <Button
+                    android:id="@+id/btnReadConfig"
+                    style="@style/Widget.MaterialComponents.Button.OutlinedButton"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_weight="1"
+                    android:layout_marginEnd="4dp"
+                    android:text="Read" />
+
+                <Button
+                    android:id="@+id/btnWriteConfig"
+                    style="@style/Widget.MaterialComponents.Button"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_weight="1"
+                    android:layout_marginStart="4dp"
+                    android:text="Write" />
+
+            </LinearLayout>
+
+            <!-- Status notifications from tag -->
+            <TextView
+                android:id="@+id/tvTagStatus"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:layout_marginTop="8dp"
+                android:background="#1A000000"
+                android:fontFamily="monospace"
+                android:padding="8dp"
+                android:text="Tag status: —"
+                android:textAppearance="@style/TextAppearance.MaterialComponents.Caption" />
+
+        </LinearLayout>
+
+    </com.google.android.material.card.MaterialCardView>
+
+</LinearLayout>

android/src/main/res/layout/item_ble_device.xml

@@ -0,0 +1,60 @@
+<?xml version="1.0" encoding="utf-8"?>
+<com.google.android.material.card.MaterialCardView
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:layout_margin="4dp"
+    app:cardElevation="2dp"
+    android:clickable="true"
+    android:focusable="true">
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="horizontal"
+        android:padding="12dp"
+        android:gravity="center_vertical">
+
+        <LinearLayout
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_weight="1"
+            android:orientation="vertical">
+
+            <TextView
+                android:id="@+id/tvDeviceName"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:text="UWB_TAG_XXXX"
+                android:textAppearance="@style/TextAppearance.MaterialComponents.Subtitle2"
+                android:textStyle="bold" />
+
+            <TextView
+                android:id="@+id/tvDeviceAddress"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:text="XX:XX:XX:XX:XX:XX"
+                android:textAppearance="@style/TextAppearance.MaterialComponents.Caption" />
+
+        </LinearLayout>
+
+        <TextView
+            android:id="@+id/tvRssi"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="-70 dBm"
+            android:textAppearance="@style/TextAppearance.MaterialComponents.Caption"
+            android:textColor="?attr/colorSecondary" />
+
+        <Button
+            android:id="@+id/btnConnect"
+            style="@style/Widget.MaterialComponents.Button.OutlinedButton"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginStart="8dp"
+            android:text="Connect" />
+
+    </LinearLayout>
+
+</com.google.android.material.card.MaterialCardView>

cad/assembly.scad

@@ -0,0 +1,118 @@
+// ============================================
+// SaltyLab — Full Assembly Visualization
+// Shows all parts in position on 2020 spine
+// ============================================
+include <dimensions.scad>
+
+// Spine height
+spine_h = 500;
+
+// Component heights (center of each mount on spine)
+h_motor = 0;
+h_battery = 50;
+h_esc = 100;
+h_fc = 170;
+h_jetson = 250;
+h_realsense = 350;
+h_lidar = 430;
+
+// Colors for visualization
+module spine() {
+    color("silver")
+        translate([-extrusion_w/2, -extrusion_w/2, 0])
+            cube([extrusion_w, extrusion_w, spine_h]);
+}
+
+module wheel(side) {
+    color("DimGray")
+        translate([side * 140, 0, 0])
+            rotate([0, 90, 0])
+                cylinder(d=200, h=50, center=true, $fn=60);
+}
+
+// --- Assembly ---
+
+// Spine
+spine();
+
+// Wheels
+wheel(-1);
+wheel(1);
+
+// Motor mount plate (at base)
+color("DodgerBlue", 0.7)
+    translate([0, 0, h_motor])
+        import("motor_mount_plate.stl");
+
+// Battery shelf
+color("OrangeRed", 0.7)
+    translate([0, 0, h_battery])
+        rotate([0, 0, 0])
+            cube([180, 80, 40], center=true);
+
+// ESC
+color("Green", 0.7)
+    translate([0, 0, h_esc])
+        cube([80, 50, 15], center=true);
+
+// FC (tiny!)
+color("Purple", 0.9)
+    translate([0, 0, h_fc])
+        cube([36, 36, 5], center=true);
+
+// Jetson Orin Nano Super
+color("LimeGreen", 0.7)
+    translate([0, 0, h_jetson])
+        cube([100, 80, 29], center=true);
+
+// RealSense D435i
+color("Gray", 0.8)
+    translate([0, -40, h_realsense])
+        cube([90, 25, 25], center=true);
+
+// RPLIDAR A1
+color("Cyan", 0.7)
+    translate([0, 0, h_lidar])
+        cylinder(d=70, h=41, center=true, $fn=40);
+
+// Kill switch (accessible on front)
+color("Red")
+    translate([0, -60, h_esc + 30])
+        cylinder(d=22, h=10, $fn=30);
+
+// LED ring
+color("White", 0.3)
+    translate([0, 0, h_jetson - 20])
+        difference() {
+            cylinder(d=120, h=15, $fn=60);
+            translate([0, 0, -1])
+                cylinder(d=110, h=17, $fn=60);
+        }
+
+// Bumpers
+color("Orange", 0.5) {
+    translate([0, -75, 25])
+        cube([350, 30, 50], center=true);
+    translate([0, 75, 25])
+        cube([350, 30, 50], center=true);
+}
+
+// Handle (top)
+color("Yellow", 0.7)
+    translate([0, 0, spine_h + 10])
+        cube([100, 20, 25], center=true);
+
+// Tether point
+color("Red", 0.8)
+    translate([0, 0, spine_h - 20]) {
+        difference() {
+            cylinder(d=30, h=8, $fn=30);
+            translate([0, 0, -1])
+                cylinder(d=15, h=10, $fn=30);
+        }
+    }
+
+echo("=== SaltyLab Assembly ===");
+echo(str("Total height: ", spine_h + 30, "mm"));
+echo(str("Width (axle-axle): ", 280 + 50*2, "mm"));
+echo(str("Depth: ~", 150, "mm"));

cad/battery_shelf.scad

@@ -0,0 +1,77 @@
+// ============================================
+// SaltyLab — Battery Shelf
+// 200×100×40mm PETG
+// Holds 36V battery pack low on the frame
+// Mounts to 2020 extrusion spine
+// ============================================
+include <dimensions.scad>
+
+shelf_w = 200;
+shelf_d = 100;
+shelf_h = 40;
+floor_h = 3;     // Bottom plate
+
+// Battery pocket (with tolerance)
+pocket_w = batt_w + tol*2;
+pocket_d = batt_d + tol*2;
+pocket_h = batt_h + 5;  // Slightly taller than battery
+
+// Velcro strap slots
+strap_w = 25;
+strap_h = 3;
+
+module battery_shelf() {
+    difference() {
+        union() {
+            // Floor
+            translate([-shelf_w/2, -shelf_d/2, 0])
+                cube([shelf_w, shelf_d, floor_h]);
+            
+            // Walls (3 sides — front open for wires)
+            // Left wall
+            translate([-shelf_w/2, -shelf_d/2, 0])
+                cube([wall, shelf_d, shelf_h]);
+            // Right wall
+            translate([shelf_w/2 - wall, -shelf_d/2, 0])
+                cube([wall, shelf_d, shelf_h]);
+            // Back wall
+            translate([-shelf_w/2, shelf_d/2 - wall, 0])
+                cube([shelf_w, wall, shelf_h]);
+            
+            // Front lip (low, keeps battery from sliding out)
+            translate([-shelf_w/2, -shelf_d/2, 0])
+                cube([shelf_w, wall, 10]);
+            
+            // 2020 extrusion mount tabs (top of back wall)
+            for (x = [-30, 30]) {
+                translate([x - 10, shelf_d/2 - wall, shelf_h - 15])
+                    cube([20, wall + 10, 15]);
+            }
+        }
+        
+        // Extrusion bolt holes (M5) through back mount tabs
+        for (x = [-30, 30]) {
+            translate([x, shelf_d/2 + 5, shelf_h - 7.5])
+                rotate([90, 0, 0])
+                    cylinder(d=m5_clear, h=wall + 15, $fn=30);
+        }
+        
+        // Velcro strap slots (2x through floor for securing battery)
+        for (x = [-50, 50]) {
+            translate([x - strap_w/2, -20, -1])
+                cube([strap_w, strap_h, floor_h + 2]);
+        }
+        
+        // Weight reduction holes in floor
+        for (x = [-30, 30]) {
+            translate([x, 0, -1])
+                cylinder(d=20, h=floor_h + 2, $fn=30);
+        }
+        
+        // Wire routing slot (front wall, centered)
+        translate([-20, -shelf_d/2 - 1, floor_h])
+            cube([40, wall + 2, 15]);
+    }
+}
+
+battery_shelf();

cad/bumper.scad

@@ -0,0 +1,75 @@
+// ============================================
+// SaltyLab — Bumper (Front/Rear)
+// 350×50×30mm TPU
+// Absorbs falls, protects frame and floor
+// ============================================
+include <dimensions.scad>
+
+bumper_w = 350;
+bumper_h = 50;
+bumper_d = 30;
+bumper_wall = 2.5;
+
+// Honeycomb crush structure for energy absorption
+hex_size = 8;
+hex_wall = 1.2;
+
+module honeycomb_cell(size, height) {
+    difference() {
+        cylinder(d=size, h=height, $fn=6);
+        translate([0, 0, -1])
+            cylinder(d=size - hex_wall*2, h=height + 2, $fn=6);
+    }
+}
+
+module bumper() {
+    difference() {
+        union() {
+            // Outer shell (curved front face)
+            hull() {
+                translate([-bumper_w/2, 0, 0])
+                    cube([bumper_w, 1, bumper_h]);
+                translate([-bumper_w/2 + 10, bumper_d - 5, 5])
+                    cube([bumper_w - 20, 1, bumper_h - 10]);
+            }
+        }
+        
+        // Hollow interior (leave outer shell)
+        hull() {
+            translate([-bumper_w/2 + bumper_wall, bumper_wall, bumper_wall])
+                cube([bumper_w - bumper_wall*2, 1, bumper_h - bumper_wall*2]);
+            translate([-bumper_w/2 + 10 + bumper_wall, bumper_d - 5 - bumper_wall, 5 + bumper_wall])
+                cube([bumper_w - 20 - bumper_wall*2, 1, bumper_h - 10 - bumper_wall*2]);
+        }
+        
+        // Mounting bolt holes (M5, through back face, 4 points)
+        for (x = [-120, -40, 40, 120]) {
+            translate([x, -1, bumper_h/2])
+                rotate([-90, 0, 0])
+                    cylinder(d=m5_clear, h=10, $fn=25);
+        }
+    }
+    
+    // Internal honeycomb ribs for crush absorption
+    intersection() {
+        // Bound to bumper volume
+        hull() {
+            translate([-bumper_w/2 + bumper_wall, bumper_wall, bumper_wall])
+                cube([bumper_w - bumper_wall*2, 1, bumper_h - bumper_wall*2]);
+            translate([-bumper_w/2 + 15, bumper_d - 8, 8])
+                cube([bumper_w - 30, 1, bumper_h - 16]);
+        }
+        
+        // Honeycomb grid
+        for (x = [-170:hex_size*1.5:170]) {
+            for (z = [0:hex_size*1.3:60]) {
+                offset_x = (floor(z / (hex_size*1.3)) % 2) * hex_size * 0.75;
+                translate([x + offset_x, 0, z])
+                    rotate([-90, 0, 0])
+                        honeycomb_cell(hex_size, bumper_d);
+            }
+        }
+    }
+}
+
+bumper();

cad/dimensions.scad

@@ -0,0 +1,73 @@
+// ============================================
+// SaltyLab — Common Dimensions & Constants
+// ============================================
+
+// --- 2020 Aluminum Extrusion ---
+extrusion_w = 20;
+extrusion_slot = 6;     // T-slot width
+extrusion_bore = 5;     // Center bore M5
+
+// --- Hub Motors (8" hoverboard) ---
+motor_axle_dia = 12;
+motor_axle_len = 45;
+motor_axle_flat = 10;   // Flat-to-flat if D-shaft
+motor_body_dia = 200;   // ~8 inches
+motor_bolt_circle = 0;  // Axle-only mount (clamp style)
+
+// --- Drone FC (30.5mm standard) ---
+fc_hole_spacing = 25.5;  // GEP-F722 AIO v2 (not standard 30.5!)
+fc_hole_dia = 3.2;      // M3 clearance
+fc_board_size = 36;      // Typical FC PCB
+fc_standoff_h = 5;       // Rubber standoff height
+
+// --- Jetson Orin Nano Super ---
+jetson_w = 100;
+jetson_d = 80;
+jetson_h = 29;           // With heatsink
+jetson_hole_x = 86;      // Mounting hole spacing X
+jetson_hole_y = 58;      // Mounting hole spacing Y
+jetson_hole_dia = 2.7;   // M2.5 clearance
+
+// --- RealSense D435i ---
+rs_w = 90;
+rs_d = 25;
+rs_h = 25;
+rs_tripod_offset = 0;    // 1/4-20 centered bottom
+rs_mount_dia = 6.5;      // 1/4-20 clearance
+
+// --- RPLIDAR A1 ---
+lidar_dia = 70;
+lidar_h = 41;
+lidar_mount_circle = 67; // Bolt circle diameter
+lidar_hole_count = 4;
+lidar_hole_dia = 2.7;    // M2.5
+
+// --- Kill Switch (22mm panel mount) ---
+kill_sw_dia = 22;
+kill_sw_depth = 35;      // Behind-panel depth
+
+// --- Battery (typical 36V hoverboard pack) ---
+batt_w = 180;
+batt_d = 80;
+batt_h = 40;
+
+// --- Hoverboard ESC ---
+esc_w = 80;
+esc_d = 50;
+esc_h = 15;
+
+// --- ESP32-C3 (typical dev board) ---
+esp_w = 25;
+esp_d = 18;
+esp_h = 5;
+
+// --- WS2812B strip ---
+led_strip_w = 10;        // 10mm wide strip
+
+// --- General ---
+wall = 3;                // Default wall thickness
+m3_clear = 3.2;
+m3_insert = 4.2;         // Heat-set insert hole
+m25_clear = 2.7;
+m5_clear = 5.3;
+tol = 0.2;               // Print tolerance per side

cad/esc_mount.scad

@@ -0,0 +1,70 @@
+// ============================================
+// SaltyLab — ESC Mount
+// 150×100×15mm PETG
+// Hoverboard ESC, mounts to 2020 extrusion
+// ============================================
+include <dimensions.scad>
+
+mount_w = 150;
+mount_d = 100;
+mount_h = 15;
+base_h = 3;
+
+module esc_mount() {
+    difference() {
+        union() {
+            // Base plate
+            translate([-mount_w/2, -mount_d/2, 0])
+                cube([mount_w, mount_d, base_h]);
+            
+            // ESC retaining walls (low lip on 3 sides)
+            // Left
+            translate([-mount_w/2, -mount_d/2, 0])
+                cube([wall, mount_d, mount_h]);
+            // Right
+            translate([mount_w/2 - wall, -mount_d/2, 0])
+                cube([wall, mount_d, mount_h]);
+            // Back
+            translate([-mount_w/2, mount_d/2 - wall, 0])
+                cube([mount_w, wall, mount_h]);
+            
+            // Front clips (snap-fit tabs to hold ESC)
+            for (x = [-30, 30]) {
+                translate([x - 5, -mount_d/2, 0])
+                    cube([10, wall, mount_h]);
+                // Clip overhang
+                translate([x - 5, -mount_d/2, mount_h - 2])
+                    cube([10, wall + 3, 2]);
+            }
+            
+            // 2020 mount tabs (back)
+            for (x = [-25, 25]) {
+                translate([x - 10, mount_d/2 - wall, 0])
+                    cube([20, wall + 8, base_h + 8]);
+            }
+        }
+        
+        // Extrusion bolt holes (M5)
+        for (x = [-25, 25]) {
+            translate([x, mount_d/2 + 3, base_h + 4])
+                rotate([90, 0, 0])
+                    cylinder(d=m5_clear, h=wall + 12, $fn=30);
+        }
+        
+        // Ventilation holes in base
+        for (x = [-40, -20, 0, 20, 40]) {
+            for (y = [-25, 0, 25]) {
+                translate([x, y, -1])
+                    cylinder(d=8, h=base_h + 2, $fn=20);
+            }
+        }
+        
+        // Wire routing slots (front and back)
+        translate([-15, -mount_d/2 - 1, base_h])
+            cube([30, wall + 2, 10]);
+        translate([-15, mount_d/2 - wall - 1, base_h])
+            cube([30, wall + 2, 10]);
+    }
+}
+
+esc_mount();

cad/esp32c3_mount.scad

@@ -0,0 +1,57 @@
+// ============================================
+// SaltyLab — ESP32-C3 Mount
+// 30×25×10mm PETG
+// Tiny mount for LED controller MCU
+// ============================================
+include <dimensions.scad>
+
+mount_w = 30;
+mount_d = 25;
+mount_h = 10;
+base_h = 2;
+
+module esp32c3_mount() {
+    difference() {
+        union() {
+            // Base
+            translate([-mount_w/2, -mount_d/2, 0])
+                cube([mount_w, mount_d, base_h]);
+            
+            // Retaining walls (3 sides, front open for USB)
+            translate([-mount_w/2, -mount_d/2, 0])
+                cube([wall, mount_d, mount_h]);
+            translate([mount_w/2 - wall, -mount_d/2, 0])
+                cube([wall, mount_d, mount_h]);
+            translate([-mount_w/2, mount_d/2 - wall, 0])
+                cube([mount_w, wall, mount_h]);
+            
+            // Clip tabs (front corners)
+            for (x = [-mount_w/2, mount_w/2 - wall]) {
+                translate([x, -mount_d/2, mount_h - 2])
+                    cube([wall, 4, 2]);
+            }
+            
+            // Zip-tie slot wings
+            for (x = [-mount_w/2 - 4, mount_w/2 + 1]) {
+                translate([x, -5, 0])
+                    cube([3, 10, base_h]);
+            }
+        }
+        
+        // Board pocket (recessed)
+        translate([-esp_w/2 - tol, -esp_d/2 - tol, base_h])
+            cube([esp_w + tol*2, esp_d + tol*2, mount_h]);
+        
+        // Zip-tie slots
+        for (x = [-mount_w/2 - 4, mount_w/2 + 1]) {
+            translate([x, -2, -1])
+                cube([3, 4, base_h + 2]);
+        }
+        
+        // USB port clearance (front)
+        translate([-5, -mount_d/2 - 1, base_h])
+            cube([10, wall + 2, 5]);
+    }
+}
+
+esp32c3_mount();

cad/fc_mount.scad

@@ -0,0 +1,86 @@
+// ============================================
+// SaltyLab — Flight Controller Mount
+// Vibration-isolated, 30.5mm pattern
+// TPU dampers + PETG frame
+// ============================================
+include <dimensions.scad>
+
+// FC mount attaches to 2020 extrusion via T-slot
+// Rubber/TPU grommets isolate FC from frame vibration
+
+mount_w = 45;    // Overall width
+mount_d = 45;    // Overall depth  
+mount_h = 15;    // Total height (base + standoffs)
+base_h = 4;      // Base plate thickness
+
+// TPU grommet dimensions
+grommet_od = 7;
+grommet_id = 3.2;  // M3 clearance
+grommet_h = 5;     // Soft mount height
+
+module fc_mount() {
+    difference() {
+        union() {
+            // Base plate
+            translate([-mount_w/2, -mount_d/2, 0])
+                cube([mount_w, mount_d, base_h]);
+            
+            // Standoff posts (PETG, FC sits on TPU grommets on top)
+            for (x = [-fc_hole_spacing/2, fc_hole_spacing/2]) {
+                for (y = [-fc_hole_spacing/2, fc_hole_spacing/2]) {
+                    translate([x, y, 0])
+                        cylinder(d=8, h=base_h + grommet_h, $fn=30);
+                }
+            }
+            
+            // 2020 extrusion clamp tabs (sides)
+            for (side = [-1, 1]) {
+                translate([side * (extrusion_w/2 + wall), -15, 0])
+                    cube([wall, 30, base_h + 10]);
+            }
+        }
+        
+        // FC mounting holes (M3 through standoffs)
+        for (x = [-fc_hole_spacing/2, fc_hole_spacing/2]) {
+            for (y = [-fc_hole_spacing/2, fc_hole_spacing/2]) {
+                translate([x, y, -1])
+                    cylinder(d=fc_hole_dia, h=base_h + grommet_h + 2, $fn=25);
+            }
+        }
+        
+        // Extrusion channel (20mm wide slot through base)
+        translate([-extrusion_w/2 - tol, -20, -1])
+            cube([extrusion_w + tol*2, 40, base_h + 2]);
+        
+        // Clamp bolt holes (M3, horizontal through side tabs)
+        for (side = [-1, 1]) {
+            translate([side * (extrusion_w/2 + wall + 1), 0, base_h + 5])
+                rotate([0, 90, 0])
+                    cylinder(d=m3_clear, h=wall + 2, center=true, $fn=25);
+        }
+        
+        // Center cutout for airflow / weight reduction
+        translate([0, 0, -1])
+            cylinder(d=15, h=base_h + 2, $fn=30);
+    }
+}
+
+// TPU grommet (print separately in TPU)
+module tpu_grommet() {
+    difference() {
+        cylinder(d=grommet_od, h=grommet_h, $fn=30);
+        translate([0, 0, -1])
+            cylinder(d=grommet_id, h=grommet_h + 2, $fn=25);
+    }
+}
+
+// Show assembled
+fc_mount();
+
+// Show grommets in position (for visualization)
+%for (x = [-fc_hole_spacing/2, fc_hole_spacing/2]) {
+    for (y = [-fc_hole_spacing/2, fc_hole_spacing/2]) {
+        translate([x, y, base_h])
+            tpu_grommet();
+    }
+}

cad/handle.scad

@@ -0,0 +1,59 @@
+// ============================================
+// SaltyLab — Carry Handle
+// 150×30×30mm PETG
+// Comfortable grip, mounts on top of spine
+// ============================================
+include <dimensions.scad>
+
+handle_w = 150;
+handle_h = 30;
+grip_dia = 25;     // Comfortable grip diameter
+grip_len = 100;    // Grip section length
+
+module handle() {
+    difference() {
+        union() {
+            // Grip bar (rounded for comfort)
+            translate([-grip_len/2, 0, handle_h])
+                rotate([0, 90, 0])
+                    cylinder(d=grip_dia, h=grip_len, $fn=40);
+            
+            // Left support leg
+            hull() {
+                translate([-handle_w/2, -10, 0])
+                    cube([20, 20, 3]);
+                translate([-grip_len/2, 0, handle_h])
+                    rotate([0, 90, 0])
+                        cylinder(d=grip_dia, h=5, $fn=40);
+            }
+            
+            // Right support leg
+            hull() {
+                translate([handle_w/2 - 20, -10, 0])
+                    cube([20, 20, 3]);
+                translate([grip_len/2 - 5, 0, handle_h])
+                    rotate([0, 90, 0])
+                        cylinder(d=grip_dia, h=5, $fn=40);
+            }
+        }
+        
+        // 2020 extrusion slot (center of base)
+        translate([-extrusion_w/2 - tol, -extrusion_w/2 - tol, -1])
+            cube([extrusion_w + tol*2, extrusion_w + tol*2, 5]);
+        
+        // M5 bolt holes for extrusion (2x)
+        for (x = [-30, 30]) {
+            translate([x, 0, -1])
+                cylinder(d=m5_clear, h=5, $fn=25);
+        }
+        
+        // Finger grooves on grip
+        for (x = [-30, -10, 10, 30]) {
+            translate([x, 0, handle_h])
+                rotate([0, 90, 0])
+                    cylinder(d=grip_dia + 4, h=5, center=true, $fn=40);
+        }
+    }
+}
+
+handle();

cad/jetson_shelf.scad

@@ -0,0 +1,69 @@
+// ============================================
+// SaltyLab — Jetson Orin Nano Super Shelf
+// 120×100×15mm PETG
+// Mounts Jetson Orin Nano Super to 2020 extrusion
+// ============================================
+include <dimensions.scad>
+
+shelf_w = 120;
+shelf_d = 100;
+shelf_h = 15;
+base_h = 3;
+standoff_h = 8;  // Clearance for Jetson underside components
+
+module jetson_shelf() {
+    difference() {
+        union() {
+            // Base plate
+            translate([-shelf_w/2, -shelf_d/2, 0])
+                cube([shelf_w, shelf_d, base_h]);
+            
+            // Jetson standoffs (M2.5, 86mm × 58mm pattern)
+            for (x = [-jetson_hole_x/2, jetson_hole_x/2]) {
+                for (y = [-jetson_hole_y/2, jetson_hole_y/2]) {
+                    translate([x, y, 0])
+                        cylinder(d=6, h=base_h + standoff_h, $fn=25);
+                }
+            }
+            
+            // 2020 extrusion clamp (back edge)
+            translate([-15, shelf_d/2 - wall, 0])
+                cube([30, wall + 10, base_h + 12]);
+            
+            // Side rails for Jetson alignment
+            for (x = [-jetson_w/2 - wall, jetson_w/2]) {
+                translate([x, -jetson_d/2, base_h + standoff_h])
+                    cube([wall, jetson_d, 4]);
+            }
+        }
+        
+        // Jetson M2.5 holes (through standoffs)
+        for (x = [-jetson_hole_x/2, jetson_hole_x/2]) {
+            for (y = [-jetson_hole_y/2, jetson_hole_y/2]) {
+                translate([x, y, -1])
+                    cylinder(d=jetson_hole_dia, h=base_h + standoff_h + 2, $fn=25);
+            }
+        }
+        
+        // Extrusion bolt hole (M5, through back clamp)
+        translate([0, shelf_d/2 + 3, base_h + 6])
+            rotate([90, 0, 0])
+                cylinder(d=m5_clear, h=wall + 15, $fn=30);
+        
+        // Extrusion channel slot
+        translate([-extrusion_w/2 - tol, shelf_d/2 - wall - 1, -1])
+            cube([extrusion_w + tol*2, wall + 2, base_h + 2]);
+        
+        // Ventilation / cable routing
+        for (x = [-25, 0, 25]) {
+            translate([x, 0, -1])
+                cylinder(d=15, h=base_h + 2, $fn=25);
+        }
+        
+        // USB/Ethernet/GPIO access cutouts (front edge)
+        translate([-jetson_w/2, -shelf_d/2 - 1, base_h])
+            cube([jetson_w, wall + 2, shelf_h]);
+    }
+}
+
+jetson_shelf();

cad/kill_switch_mount.scad

@@ -0,0 +1,56 @@
+// ============================================
+// SaltyLab — Kill Switch Mount
+// 60×60×40mm PETG
+// 22mm panel-mount emergency stop button
+// Mounts to 2020 extrusion, easily reachable
+// ============================================
+include <dimensions.scad>
+
+mount_w = 60;
+mount_d = 60;
+mount_h = 40;
+panel_h = 3;  // Panel face thickness
+
+module kill_switch_mount() {
+    difference() {
+        union() {
+            // Main body (angled face for visibility)
+            hull() {
+                translate([-mount_w/2, 0, 0])
+                    cube([mount_w, mount_d, 1]);
+                translate([-mount_w/2, 5, mount_h])
+                    cube([mount_w, mount_d - 5, 1]);
+            }
+            
+            // 2020 extrusion mount bracket (back)
+            translate([-15, mount_d, 0])
+                cube([30, 10, 20]);
+        }
+        
+        // Kill switch hole (22mm, through angled face)
+        translate([0, mount_d/2, mount_h/2])
+            rotate([10, 0, 0])  // Slight angle for ergonomics
+                cylinder(d=kill_sw_dia + tol, h=panel_h + 2, center=true, $fn=50);
+        
+        // Interior cavity (hollow for switch body)
+        translate([-kill_sw_dia/2 - 3, 5, 3])
+            cube([kill_sw_dia + 6, mount_d - 10, mount_h - 3]);
+        
+        // Wire exit hole (bottom)
+        translate([0, mount_d/2, -1])
+            cylinder(d=10, h=5, $fn=25);
+        
+        // Extrusion bolt holes (M5, through back bracket)
+        for (z = [7, 15]) {
+            translate([-20, mount_d + 5, z])
+                rotate([90, 0, 0])
+                    cylinder(d=m5_clear, h=15, center=true, $fn=25);
+        }
+        
+        // Label recess ("EMERGENCY STOP" — flat area for sticker)
+        translate([-25, 5, mount_h - 1])
+            cube([50, 15, 1.5]);
+    }
+}
+
+kill_switch_mount();