diff --git a/ROADMAP.md b/ROADMAP.md
index 8dd76aa..f21193c 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -122,98 +122,42 @@ Using relative paths for portability across systems:
 
 ---
 
-### Phase 2: Python Package Structure ✓ TODO
+### Phase 2: Python Package Structure ✅ DONE (2025-12-27)
 **Goal**: Create modern Python package with proper entry point
 
+**Notes**:
+- Used src/ layout for better packaging practices
+- Direct Python MQTT integration (no shell script callbacks)
+- ATC firmware BLE advertisement reading (passive scanning)
+- Watchdog thread for BLE connection recovery
+- Clean separation of concerns (config, MQTT, sensors, main)
+
 #### Tasks:
-1. Create `src/sensorpajen/__init__.py`
-   - Package initialization
-   - Version information
-
-2. Create `src/sensorpajen/config.py`
-   - Environment variable loading
-   - Configuration validation
-   - Default values
-   - Fail-fast on missing required config
-   ```python
-   import os
-   import json
-   from pathlib import Path
-
-   # MQTT Configuration from environment
-   MQTT_HOST = os.environ.get("MQTT_HOST")
-   MQTT_PORT = int(os.environ.get("MQTT_PORT", "1883"))
-   MQTT_USER = os.environ.get("MQTT_USER")
-   MQTT_PASSWORD = os.environ.get("MQTT_PASSWORD")
-   MQTT_CLIENT_ID = os.environ.get("MQTT_CLIENT_ID", "sensorpajen")
-   
-   # Validate required config
-   if not MQTT_HOST:
-       raise RuntimeError("MQTT_HOST environment variable must be set")
-    (relative to project root)
-   PROJECT_ROOT = Path(__file__).parent.parent.parent
-   SENSOR_CONFIG_FILE = os.environ.get(
-       "SENSOR_CONFIG_FILE",
-       str(PROJECT_ROOT / "config
-       str(Path.home() / ".config/sensorpajen/sensors.json")
-   )
-   
-   # Bluetooth settings
-   WATCHDOG_TIMEOUT = int(os.environ.get("WATCHDOG_TIMEOUT", "5"))
-   ENABLE_BATTERY = os.environ.get("ENABLE_BATTERY", "true").lower() == "true"
-   ```
-
-3. Create `src/sensorpajen/utils.py`
-   - Port bluetooth_utils.py functionality
-   - Clean up and modernize
-
-4. Create `src/sensorpajen/sensor_reader.py`
-   - Extract sensor reading logic from LYWSD03MMC.py
-   - Remove callback/shell script dependency
-   - Direct Python MQTT integration
-
-5. Create `src/sensorpajen/mqtt_publisher.py`
-   - MQTT client setup and connection
-   - Publishing logic (replacing sendToMQTT.sh)
-   - Error handling and reconnection
-
-6. Create `src/sensorpajen/main.py`
-   - Entry point for the application
-   - Signal handling (SIGTERM, SIGINT)
-   - Logging setup (to stdout for journald)
-   - Main loop
-   ```python
-   #!/usr/bin/env python3
-   import logging
-   import signal
-   import sys
-   from . import config
-   from .sensor_reader import SensorReader
-   from .mqtt_publisher import MQTTPublisher
-   
-   def main():
-       logging.basicConfig(
-           level=logging.INFO,
-           format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
-           stream=sys.stdout
-       )
-       logger = logging.getLogger(__name__)
-       logger.info("Starting sensorpajen service")
-       
-       # Setup signal handlers
-       def signal_handler(sig, frame):
-           logger.info("Received shutdown signal")
-           sys.exit(0)
-       
-       signal.signal(signal.SIGTERM, signal_handler)
-       signal.signal(signal.SIGINT, signal_handler)
-       
-       # Main application logic here
-       # ...
-   
-   if __name__ == "__main__":
-       main()
-   ```
+- ✅ Created src/sensorpajen/__init__.py with version info
+- ✅ Created src/sensorpajen/config.py
+  - Environment variable loading with validation
+  - SensorConfig class for JSON sensor mapping
+  - Relative path resolution (PROJECT_ROOT)
+  - Configuration validation and logging
+- ✅ Created src/sensorpajen/utils.py
+  - Ported bluetooth_utils.py (MIT licensed, Colin GUYON)
+  - BLE scanning and advertisement parsing
+- ✅ Created src/sensorpajen/mqtt_publisher.py
+  - MQTTPublisher class with connection management
+  - Direct publishing (replaces sendToMQTT.sh)
+  - Automatic reconnection support
+  - Battery data publishing (optional)
+- ✅ Created src/sensorpajen/sensor_reader.py
+  - SensorReader class for BLE scanning
+  - ATC packet parsing
+  - Duplicate packet filtering
+  - Watchdog for BLE recovery
+  - Measurement dataclass
+- ✅ Created src/sensorpajen/main.py
+  - Application entry point
+  - Signal handling (SIGTERM, SIGINT)
+  - Graceful shutdown
+  - Logging to stdout for journald
 
 ---
 
diff --git a/src/sensorpajen/config.py b/src/sensorpajen/config.py
new file mode 100644
index 0000000..db9359e
--- /dev/null
+++ b/src/sensorpajen/config.py
@@ -0,0 +1,124 @@
+"""
+Configuration management for Sensorpajen.
+
+Loads configuration from environment variables with sensible defaults.
+Configuration files are loaded relative to the project root.
+"""
+
+import os
+import json
+import logging
+from pathlib import Path
+from typing import Dict, List
+
+logger = logging.getLogger(__name__)
+
+# Determine project root (3 levels up from this file: src/sensorpajen/config.py)
+PROJECT_ROOT = Path(__file__).parent.parent.parent
+
+# MQTT Configuration from environment
+MQTT_HOST = os.environ.get("MQTT_HOST")
+MQTT_PORT = int(os.environ.get("MQTT_PORT", "1883"))
+MQTT_USER = os.environ.get("MQTT_USER")
+MQTT_PASSWORD = os.environ.get("MQTT_PASSWORD")
+MQTT_CLIENT_ID = os.environ.get("MQTT_CLIENT_ID", "sensorpajen")
+MQTT_TOPIC_PREFIX = os.environ.get("MQTT_TOPIC_PREFIX", "MiTemperature2")
+
+# Validate required MQTT configuration
+if not MQTT_HOST:
+    raise RuntimeError(
+        "MQTT_HOST environment variable must be set. "
+        "Please configure config/sensorpajen.env"
+    )
+
+# Sensor configuration file (relative to project root)
+SENSOR_CONFIG_FILE = os.environ.get(
+    "SENSOR_CONFIG_FILE",
+    str(PROJECT_ROOT / "config/sensors.json")
+)
+
+# Application settings
+WATCHDOG_TIMEOUT = int(os.environ.get("WATCHDOG_TIMEOUT", "5"))
+ENABLE_BATTERY = os.environ.get("ENABLE_BATTERY", "true").lower() == "true"
+LOG_LEVEL = os.environ.get("LOG_LEVEL", "INFO").upper()
+
+# Bluetooth settings
+SKIP_IDENTICAL = int(os.environ.get("SKIP_IDENTICAL", "50"))
+DEBOUNCE = os.environ.get("DEBOUNCE", "true").lower() == "true"
+
+
+class SensorConfig:
+    """Manages sensor configuration from JSON file."""
+    
+    def __init__(self, config_file: str = SENSOR_CONFIG_FILE):
+        """
+        Initialize sensor configuration.
+        
+        Args:
+            config_file: Path to sensors JSON configuration file
+        """
+        self.config_file = Path(config_file)
+        self.sensors: Dict[str, str] = {}
+        self.load()
+    
+    def load(self):
+        """Load sensor configuration from JSON file."""
+        if not self.config_file.exists():
+            raise FileNotFoundError(
+                f"Sensor configuration file not found: {self.config_file}\n"
+                f"Please copy config/sensors.json.example to config/sensors.json "
+                f"and configure your sensors."
+            )
+        
+        try:
+            with open(self.config_file, 'r') as f:
+                data = json.load(f)
+            
+            # Convert sensors list to MAC -> name mapping
+            for sensor in data.get('sensors', []):
+                mac = sensor.get('mac', '').upper()
+                name = sensor.get('name')
+                
+                if mac and name:
+                    self.sensors[mac] = name
+                    logger.debug(f"Loaded sensor: {mac} -> {name}")
+            
+            logger.info(f"Loaded {len(self.sensors)} sensors from {self.config_file}")
+            
+        except json.JSONDecodeError as e:
+            raise RuntimeError(f"Invalid JSON in {self.config_file}: {e}")
+        except Exception as e:
+            raise RuntimeError(f"Error loading sensor config: {e}")
+    
+    def get_name(self, mac: str) -> str:
+        """
+        Get sensor name by MAC address.
+        
+        Args:
+            mac: MAC address (any case)
+            
+        Returns:
+            Sensor name or the MAC address if not found
+        """
+        return self.sensors.get(mac.upper(), mac)
+    
+    def get_all_macs(self) -> List[str]:
+        """Get list of all configured MAC addresses."""
+        return list(self.sensors.keys())
+
+
+def validate_config():
+    """
+    Validate configuration and log settings.
+    Should be called at application startup.
+    """
+    logger.info("=== Sensorpajen Configuration ===")
+    logger.info(f"MQTT Host: {MQTT_HOST}:{MQTT_PORT}")
+    logger.info(f"MQTT User: {MQTT_USER}")
+    logger.info(f"MQTT Client ID: {MQTT_CLIENT_ID}")
+    logger.info(f"MQTT Topic Prefix: {MQTT_TOPIC_PREFIX}")
+    logger.info(f"Sensor Config: {SENSOR_CONFIG_FILE}")
+    logger.info(f"Watchdog Timeout: {WATCHDOG_TIMEOUT}s")
+    logger.info(f"Battery Monitoring: {ENABLE_BATTERY}")
+    logger.info(f"Log Level: {LOG_LEVEL}")
+    logger.info("================================")
diff --git a/src/sensorpajen/main.py b/src/sensorpajen/main.py
new file mode 100644
index 0000000..e696d3c
--- /dev/null
+++ b/src/sensorpajen/main.py
@@ -0,0 +1,168 @@
+#!/usr/bin/env python3
+"""
+Sensorpajen - Main entry point
+
+Bluetooth temperature sensor monitor for Xiaomi Mijia LYWSD03MMC sensors.
+Publishes sensor data to MQTT broker.
+"""
+
+import sys
+import signal
+import logging
+import time
+from pathlib import Path
+
+from . import __version__
+from . import config
+from .mqtt_publisher import MQTTPublisher
+from .sensor_reader import SensorReader, Measurement
+
+
+class Sensorpajen:
+    """Main application class."""
+    
+    def __init__(self):
+        """Initialize the application."""
+        self.mqtt_publisher: MQTTPublisher = None
+        self.sensor_reader: SensorReader = None
+        self.sensor_config: config.SensorConfig = None
+        self.running = False
+        
+        # Setup logging
+        self._setup_logging()
+        
+        # Setup signal handlers
+        signal.signal(signal.SIGTERM, self._signal_handler)
+        signal.signal(signal.SIGINT, self._signal_handler)
+    
+    def _setup_logging(self):
+        """Configure logging to stdout for journald."""
+        log_level = getattr(logging, config.LOG_LEVEL, logging.INFO)
+        
+        logging.basicConfig(
+            level=log_level,
+            format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
+            stream=sys.stdout
+        )
+        
+        # Set our logger
+        self.logger = logging.getLogger(__name__)
+    
+    def _signal_handler(self, sig, frame):
+        """Handle shutdown signals."""
+        signal_name = "SIGTERM" if sig == signal.SIGTERM else "SIGINT"
+        self.logger.info(f"Received {signal_name}, shutting down gracefully...")
+        self.shutdown()
+        sys.exit(0)
+    
+    def _on_measurement(self, measurement: Measurement):
+        """
+        Callback for new sensor measurements.
+        
+        Args:
+            measurement: Sensor measurement data
+        """
+        try:
+            # Publish to MQTT
+            self.mqtt_publisher.publish_measurement(
+                sensor_name=measurement.sensor_name,
+                temperature=measurement.temperature,
+                humidity=measurement.humidity,
+                battery_voltage=measurement.voltage,
+                battery_level=measurement.battery
+            )
+        except Exception as e:
+            self.logger.error(f"Error handling measurement: {e}")
+    
+    def start(self):
+        """Start the application."""
+        try:
+            self.logger.info("=" * 50)
+            self.logger.info(f"Starting Sensorpajen v{__version__}")
+            self.logger.info("=" * 50)
+            
+            # Validate and log configuration
+            config.validate_config()
+            
+            # Load sensor configuration
+            self.sensor_config = config.SensorConfig()
+            
+            if len(self.sensor_config.sensors) == 0:
+                self.logger.error("No sensors configured!")
+                self.logger.error("Please configure sensors in config/sensors.json")
+                sys.exit(1)
+            
+            # Initialize MQTT publisher
+            self.logger.info("Initializing MQTT publisher...")
+            self.mqtt_publisher = MQTTPublisher()
+            self.mqtt_publisher.connect()
+            
+            # Wait a moment for MQTT connection
+            time.sleep(1)
+            
+            if not self.mqtt_publisher.is_connected():
+                self.logger.warning("MQTT connection not established yet, continuing anyway...")
+            
+            # Initialize sensor reader
+            self.logger.info("Initializing Bluetooth sensor reader...")
+            self.sensor_reader = SensorReader(
+                sensor_config=self.sensor_config,
+                on_measurement=self._on_measurement,
+                interface=0  # hci0
+            )
+            
+            # Start reading sensors (blocking call)
+            self.logger.info("=" * 50)
+            self.logger.info("Sensorpajen is now running")
+            self.logger.info("Monitoring sensors via Bluetooth...")
+            self.logger.info("Publishing to MQTT...")
+            self.logger.info("Press Ctrl+C to stop")
+            self.logger.info("=" * 50)
+            
+            self.running = True
+            self.sensor_reader.start()
+            
+        except FileNotFoundError as e:
+            self.logger.error(f"Configuration error: {e}")
+            sys.exit(1)
+        except RuntimeError as e:
+            self.logger.error(f"Configuration error: {e}")
+            sys.exit(1)
+        except Exception as e:
+            self.logger.error(f"Failed to start application: {e}", exc_info=True)
+            self.shutdown()
+            sys.exit(1)
+    
+    def shutdown(self):
+        """Shutdown the application gracefully."""
+        if not self.running:
+            return
+        
+        self.running = False
+        self.logger.info("Shutting down...")
+        
+        # Stop sensor reader
+        if self.sensor_reader:
+            try:
+                self.sensor_reader.stop()
+            except Exception as e:
+                self.logger.error(f"Error stopping sensor reader: {e}")
+        
+        # Disconnect MQTT
+        if self.mqtt_publisher:
+            try:
+                self.mqtt_publisher.disconnect()
+            except Exception as e:
+                self.logger.error(f"Error disconnecting MQTT: {e}")
+        
+        self.logger.info("Shutdown complete")
+
+
+def main():
+    """Main entry point."""
+    app = Sensorpajen()
+    app.start()
+
+
+if __name__ == "__main__":
+    main()
diff --git a/src/sensorpajen/mqtt_publisher.py b/src/sensorpajen/mqtt_publisher.py
new file mode 100644
index 0000000..5583fb1
--- /dev/null
+++ b/src/sensorpajen/mqtt_publisher.py
@@ -0,0 +1,122 @@
+"""
+MQTT Publisher for sensor data.
+
+Handles connection to MQTT broker and publishing of sensor measurements.
+"""
+
+import logging
+import paho.mqtt.client as mqtt
+from typing import Optional
+from . import config
+
+logger = logging.getLogger(__name__)
+
+
+class MQTTPublisher:
+    """Manages MQTT connection and publishing of sensor data."""
+    
+    def __init__(self):
+        """Initialize MQTT publisher with configuration."""
+        self.client: Optional[mqtt.Client] = None
+        self.connected = False
+        self._setup_client()
+    
+    def _setup_client(self):
+        """Setup MQTT client with callbacks."""
+        self.client = mqtt.Client(config.MQTT_CLIENT_ID)
+        
+        # Set credentials if provided
+        if config.MQTT_USER and config.MQTT_PASSWORD:
+            self.client.username_pw_set(config.MQTT_USER, config.MQTT_PASSWORD)
+        
+        # Setup callbacks
+        self.client.on_connect = self._on_connect
+        self.client.on_disconnect = self._on_disconnect
+        self.client.on_publish = self._on_publish
+        
+        logger.info(f"MQTT client configured for {config.MQTT_HOST}:{config.MQTT_PORT}")
+    
+    def _on_connect(self, client, userdata, flags, rc):
+        """Callback for when client connects to broker."""
+        if rc == 0:
+            self.connected = True
+            logger.info(f"Connected to MQTT broker at {config.MQTT_HOST}:{config.MQTT_PORT}")
+        else:
+            self.connected = False
+            logger.error(f"Failed to connect to MQTT broker. Return code: {rc}")
+    
+    def _on_disconnect(self, client, userdata, rc):
+        """Callback for when client disconnects from broker."""
+        self.connected = False
+        if rc != 0:
+            logger.warning(f"Unexpected disconnection from MQTT broker. Return code: {rc}")
+        else:
+            logger.info("Disconnected from MQTT broker")
+    
+    def _on_publish(self, client, userdata, mid):
+        """Callback for when message is published."""
+        logger.debug(f"Message published: {mid}")
+    
+    def connect(self):
+        """Connect to MQTT broker."""
+        try:
+            logger.info(f"Connecting to MQTT broker at {config.MQTT_HOST}:{config.MQTT_PORT}")
+            self.client.connect(config.MQTT_HOST, config.MQTT_PORT, keepalive=60)
+            self.client.loop_start()  # Start network loop in background thread
+        except Exception as e:
+            logger.error(f"Failed to connect to MQTT broker: {e}")
+            raise
+    
+    def disconnect(self):
+        """Disconnect from MQTT broker."""
+        if self.client:
+            self.client.loop_stop()
+            self.client.disconnect()
+            logger.info("Disconnected from MQTT broker")
+    
+    def publish_measurement(self, sensor_name: str, temperature: float, 
+                          humidity: int, battery_voltage: float = None, 
+                          battery_level: int = None):
+        """
+        Publish sensor measurement to MQTT.
+        
+        Args:
+            sensor_name: Name of the sensor
+            temperature: Temperature in Celsius
+            humidity: Humidity percentage
+            battery_voltage: Battery voltage (optional)
+            battery_level: Battery level percentage (optional)
+        """
+        if not self.connected:
+            logger.warning("Not connected to MQTT broker, skipping publish")
+            return
+        
+        topic_prefix = f"{config.MQTT_TOPIC_PREFIX}/{sensor_name}"
+        
+        try:
+            # Publish temperature
+            self.client.publish(f"{topic_prefix}/temp", f"{temperature:.1f}")
+            logger.debug(f"{sensor_name}: temp={temperature:.1f}°C")
+            
+            # Publish humidity
+            self.client.publish(f"{topic_prefix}/humidity", f"{humidity}")
+            logger.debug(f"{sensor_name}: humidity={humidity}%")
+            
+            # Publish battery info if enabled and available
+            if config.ENABLE_BATTERY:
+                if battery_voltage is not None:
+                    self.client.publish(f"{topic_prefix}/batteryvoltage", f"{battery_voltage:.3f}")
+                    logger.debug(f"{sensor_name}: battery_voltage={battery_voltage:.3f}V")
+                
+                if battery_level is not None:
+                    self.client.publish(f"{topic_prefix}/batterylevel", f"{battery_level}")
+                    logger.debug(f"{sensor_name}: battery_level={battery_level}%")
+            
+            logger.info(f"Published: {sensor_name} - {temperature:.1f}°C, {humidity}%")
+            
+        except Exception as e:
+            logger.error(f"Error publishing to MQTT: {e}")
+    
+    def is_connected(self) -> bool:
+        """Check if connected to MQTT broker."""
+        return self.connected
diff --git a/src/sensorpajen/sensor_reader.py b/src/sensorpajen/sensor_reader.py
new file mode 100644
index 0000000..0264da9
--- /dev/null
+++ b/src/sensorpajen/sensor_reader.py
@@ -0,0 +1,254 @@
+"""
+Bluetooth sensor reader for Xiaomi Mijia LYWSD03MMC sensors with ATC firmware.
+
+Reads temperature, humidity, and battery data from BLE advertisements.
+"""
+
+import logging
+import time
+import threading
+import bluetooth._bluetooth as bluez
+from dataclasses import dataclass
+from typing import Optional, Callable, Dict
+
+from . import config
+from .utils import (enable_le_scan, disable_le_scan, 
+                   parse_le_advertising_events, raw_packet_to_str, toggle_device)
+
+logger = logging.getLogger(__name__)
+
+
+@dataclass
+class Measurement:
+    """Sensor measurement data."""
+    temperature: float
+    humidity: int
+    voltage: float
+    battery: int = 0
+    rssi: int = 0
+    sensor_name: str = ""
+    timestamp: int = 0
+
+
+class SensorReader:
+    """Reads Xiaomi LYWSD03MMC sensors with ATC firmware via BLE."""
+    
+    def __init__(self, sensor_config: config.SensorConfig, 
+                 on_measurement: Callable[[Measurement], None],
+                 interface: int = 0):
+        """
+        Initialize sensor reader.
+        
+        Args:
+            sensor_config: Sensor configuration mapping
+            on_measurement: Callback function for new measurements
+            interface: Bluetooth interface number (default 0 for hci0)
+        """
+        self.sensor_config = sensor_config
+        self.on_measurement = on_measurement
+        self.interface = interface
+        self.sock: Optional[int] = None
+        self.running = False
+        self.last_ble_packet = time.time()
+        self.adv_counter: Dict[str, str] = {}  # Track advertisement numbers to avoid duplicates
+        self.watchdog_thread: Optional[threading.Thread] = None
+        
+    def start(self):
+        """Start BLE scanning for sensors."""
+        try:
+            logger.info(f"Starting BLE scan on hci{self.interface}")
+            
+            # Enable bluetooth device
+            toggle_device(self.interface, True)
+            
+            # Open bluetooth socket
+            try:
+                self.sock = bluez.hci_open_dev(self.interface)
+            except Exception as e:
+                logger.error(f"Cannot open bluetooth device hci{self.interface}: {e}")
+                raise
+            
+            # Enable LE scanning without filtering duplicates
+            enable_le_scan(self.sock, filter_duplicates=False)
+            
+            # Start watchdog if configured
+            if config.WATCHDOG_TIMEOUT > 0:
+                self.running = True
+                self.watchdog_thread = threading.Thread(target=self._watchdog_loop, daemon=True)
+                self.watchdog_thread.start()
+                logger.info(f"Watchdog started with {config.WATCHDOG_TIMEOUT}s timeout")
+            
+            logger.info("BLE scanning enabled")
+            logger.info(f"Monitoring {len(self.sensor_config.sensors)} sensors")
+            
+            # Start parsing advertisements (blocking call)
+            parse_le_advertising_events(
+                self.sock,
+                handler=self._handle_ble_packet,
+                debug=False
+            )
+            
+        except KeyboardInterrupt:
+            logger.info("Received keyboard interrupt")
+            self.stop()
+        except Exception as e:
+            logger.error(f"Error in sensor reader: {e}")
+            self.stop()
+            raise
+    
+    def stop(self):
+        """Stop BLE scanning."""
+        self.running = False
+        
+        if self.sock:
+            try:
+                disable_le_scan(self.sock)
+                logger.info("BLE scanning disabled")
+            except Exception as e:
+                logger.error(f"Error disabling BLE scan: {e}")
+        
+        if self.watchdog_thread and self.watchdog_thread.is_alive():
+            self.watchdog_thread.join(timeout=2)
+    
+    def _watchdog_loop(self):
+        """Watchdog thread to restart BLE scanning if no packets received."""
+        restart_counter = 1
+        
+        while self.running:
+            time.sleep(1)
+            now = time.time()
+            elapsed = now - self.last_ble_packet
+            
+            if elapsed > config.WATCHDOG_TIMEOUT:
+                logger.warning(
+                    f"Watchdog: No BLE packet within {int(elapsed)}s. "
+                    f"Restarting BLE scan (count: {restart_counter})"
+                )
+                try:
+                    disable_le_scan(self.sock)
+                    time.sleep(1)
+                    enable_le_scan(self.sock, filter_duplicates=False)
+                    restart_counter += 1
+                    self.last_ble_packet = now  # Reset timer
+                except Exception as e:
+                    logger.error(f"Error restarting BLE scan: {e}")
+    
+    def _handle_ble_packet(self, mac: str, adv_type: int, data: bytes, rssi: int):
+        """
+        Handle incoming BLE advertisement packet.
+        
+        Args:
+            mac: MAC address of the device
+            adv_type: Advertisement type
+            data: Advertisement data
+            rssi: Signal strength
+        """
+        # Update last packet time for watchdog
+        self.last_ble_packet = time.time()
+        
+        # Convert data to hex string
+        data_str = raw_packet_to_str(data)
+        
+        # Check if this is an ATC packet
+        # ATC format: [... service UUID 0x181A ... MAC ... data ...]
+        atc_identifier = data_str[6:10].upper()
+        if atc_identifier != "1A18":
+            return  # Not an ATC packet
+        
+        # Extract MAC from packet and verify it matches
+        packet_mac = data_str[10:22].upper()
+        mac_str = mac.replace(":", "").upper()
+        
+        if packet_mac != mac_str:
+            return  # MAC mismatch
+        
+        # Check if this is a known sensor or if we accept all
+        mac_with_colons = mac.upper()
+        if mac_with_colons not in self.sensor_config.sensors:
+            logger.debug(f"Ignoring unknown sensor: {mac}")
+            return
+        
+        # Check advertisement number to avoid duplicates
+        adv_number = data_str[-2:]
+        if mac_str in self.adv_counter:
+            if self.adv_counter[mac_str] == adv_number:
+                return  # Duplicate packet
+        self.adv_counter[mac_str] = adv_number
+        
+        # Parse ATC data packet
+        try:
+            measurement = self._parse_atc_packet(data_str, mac_with_colons, rssi)
+            
+            if measurement:
+                # Log the measurement
+                logger.info(
+                    f"{measurement.sensor_name}: {measurement.temperature}°C, "
+                    f"{measurement.humidity}%, {measurement.voltage}V, "
+                    f"battery {measurement.battery}%, RSSI {rssi}dBm"
+                )
+                
+                # Call measurement callback
+                if self.on_measurement:
+                    self.on_measurement(measurement)
+                    
+        except Exception as e:
+            logger.error(f"Error parsing ATC packet from {mac}: {e}")
+    
+    def _parse_atc_packet(self, data_str: str, mac: str, rssi: int) -> Optional[Measurement]:
+        """
+        Parse ATC advertisement data packet.
+        
+        ATC packet format (after service UUID):
+        - Bytes 10-22: MAC address
+        - Bytes 22-26: Temperature (signed int16, big endian, /10 for °C)
+        - Bytes 26-28: Humidity (uint8, %)
+        - Bytes 28-30: Battery (uint8, %)
+        - Bytes 30-34: Battery voltage (uint16, big endian, /1000 for V)
+        - Bytes 34-36: Frame counter
+        
+        Args:
+            data_str: Hex string of advertisement data
+            mac: MAC address with colons
+            rssi: Signal strength
+            
+        Returns:
+            Measurement object or None if parsing failed
+        """
+        try:
+            # Extract temperature (signed, big endian)
+            temp_hex = data_str[22:26]
+            temperature = int.from_bytes(
+                bytearray.fromhex(temp_hex), 
+                byteorder='big', 
+                signed=True
+            ) / 10.0
+            
+            # Extract humidity
+            humidity = int(data_str[26:28], 16)
+            
+            # Extract battery level
+            battery = int(data_str[28:30], 16)
+            
+            # Extract battery voltage
+            voltage_hex = data_str[30:34]
+            voltage = int(voltage_hex, 16) / 1000.0
+            
+            # Get sensor name from config
+            sensor_name = self.sensor_config.get_name(mac)
+            
+            # Create measurement
+            measurement = Measurement(
+                temperature=temperature,
+                humidity=humidity,
+                voltage=voltage,
+                battery=battery,
+                rssi=rssi,
+                sensor_name=sensor_name,
+                timestamp=int(time.time())
+            )
+            
+            return measurement
+            
+        except Exception as e:
+            logger.error(f"Error parsing ATC data: {e}")
+            return None
diff --git a/src/sensorpajen/utils.py b/src/sensorpajen/utils.py
new file mode 100644
index 0000000..529599a
--- /dev/null
+++ b/src/sensorpajen/utils.py
@@ -0,0 +1,421 @@
+# -*- coding: utf-8 -*-
+# This file is from https://github.com/colin-guyon/py-bluetooth-utils 
+# published under MIT License
+
+# MIT License
+
+# Copyright (c) 2020 Colin GUYON
+
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+"""
+Module containing some bluetooth utility functions (linux only).
+
+It either uses HCI commands using PyBluez, or does ioctl calls like it's
+done in Bluez tools such as hciconfig.
+
+Main functions:
+  - toggle_device : enable or disable a bluetooth device
+  - set_scan : set scan type on a device ("noscan", "iscan", "pscan", "piscan")
+  - enable/disable_le_scan : enable BLE scanning
+  - parse_le_advertising_events : parse and read BLE advertisements packets
+  - start/stop_le_advertising : advertise custom data using BLE
+
+Bluez : http://www.bluez.org/
+PyBluez : http://karulis.github.io/pybluez/
+
+The module was in particular inspired from 'iBeacon-Scanner-'
+https://github.com/switchdoclabs/iBeacon-Scanner-/blob/master/blescan.py
+and sometimes directly from the Bluez sources.
+"""
+
+from __future__ import absolute_import
+import sys
+import struct
+import fcntl
+import array
+import socket
+from errno import EALREADY
+
+# import PyBluez
+import bluetooth._bluetooth as bluez
+
+__all__ = ('toggle_device', 'set_scan',
+           'enable_le_scan', 'disable_le_scan', 'parse_le_advertising_events',
+           'start_le_advertising', 'stop_le_advertising',
+           'raw_packet_to_str')
+
+LE_META_EVENT = 0x3E
+LE_PUBLIC_ADDRESS = 0x00
+LE_RANDOM_ADDRESS = 0x01
+
+OGF_LE_CTL = 0x08
+OCF_LE_SET_SCAN_PARAMETERS = 0x000B
+OCF_LE_SET_SCAN_ENABLE = 0x000C
+OCF_LE_CREATE_CONN = 0x000D
+OCF_LE_SET_ADVERTISING_PARAMETERS = 0x0006
+OCF_LE_SET_ADVERTISE_ENABLE = 0x000A
+OCF_LE_SET_ADVERTISING_DATA = 0x0008
+
+SCAN_TYPE_PASSIVE = 0x00
+SCAN_FILTER_DUPLICATES = 0x01
+SCAN_DISABLE = 0x00
+SCAN_ENABLE = 0x01
+
+# sub-events of LE_META_EVENT
+EVT_LE_CONN_COMPLETE = 0x01
+EVT_LE_ADVERTISING_REPORT = 0x02
+EVT_LE_CONN_UPDATE_COMPLETE = 0x03
+EVT_LE_READ_REMOTE_USED_FEATURES_COMPLETE = 0x04
+
+# Advertisement event types
+ADV_IND = 0x00
+ADV_DIRECT_IND = 0x01
+ADV_SCAN_IND = 0x02
+ADV_NONCONN_IND = 0x03
+ADV_SCAN_RSP = 0x04
+
+# Allow Scan Request from Any, Connect Request from Any
+FILTER_POLICY_NO_WHITELIST = 0x00
+# Allow Scan Request from White List Only, Connect Request from Any
+FILTER_POLICY_SCAN_WHITELIST = 0x01
+# Allow Scan Request from Any, Connect Request from White List Only
+FILTER_POLICY_CONN_WHITELIST = 0x02
+# Allow Scan Request from White List Only, Connect Request from White List Only
+FILTER_POLICY_SCAN_AND_CONN_WHITELIST = 0x03
+
+
+def toggle_device(dev_id, enable):
+    """
+    Power ON or OFF a bluetooth device.
+
+    :param dev_id: Device id.
+    :type dev_id: ``int``
+    :param enable: Whether to enable of disable the device.
+    :type enable: ``bool``
+    """
+    hci_sock = socket.socket(socket.AF_BLUETOOTH,
+                             socket.SOCK_RAW,
+                             socket.BTPROTO_HCI)
+    print("Power %s bluetooth device %d" % ('ON' if enable else 'OFF', dev_id))
+    # di = struct.pack("HbBIBBIIIHHHH10I", dev_id, *((0,) * 22))
+    # fcntl.ioctl(hci_sock.fileno(), bluez.HCIGETDEVINFO, di)
+    req_str = struct.pack("H", dev_id)
+    request = array.array("b", req_str)
+    try:
+        fcntl.ioctl(hci_sock.fileno(),
+                    bluez.HCIDEVUP if enable else bluez.HCIDEVDOWN,
+                    request[0])
+    except IOError as e:
+        if e.errno == EALREADY:
+            print("Bluetooth device %d is already %s" % (
+                  dev_id, 'enabled' if enable else 'disabled'))
+        else:
+            raise
+    finally:
+        hci_sock.close()
+
+
+# Types of bluetooth scan
+SCAN_DISABLED = 0x00
+SCAN_INQUIRY = 0x01
+SCAN_PAGE = 0x02
+
+
+def set_scan(dev_id, scan_type):
+    """
+    Set scan type on a given bluetooth device.
+
+    :param dev_id: Device id.
+    :type dev_id: ``int``
+    :param scan_type: One of
+        ``'noscan'``
+        ``'iscan'``
+        ``'pscan'``
+        ``'piscan'``
+    :type scan_type: ``str``
+    """
+    hci_sock = socket.socket(socket.AF_BLUETOOTH,
+                             socket.SOCK_RAW,
+                             socket.BTPROTO_HCI)
+    if scan_type == "noscan":
+        dev_opt = SCAN_DISABLED
+    elif scan_type == "iscan":
+        dev_opt = SCAN_INQUIRY
+    elif scan_type == "pscan":
+        dev_opt = SCAN_PAGE
+    elif scan_type == "piscan":
+        dev_opt = SCAN_PAGE | SCAN_INQUIRY
+    else:
+        raise ValueError("Unknown scan type %r" % scan_type)
+
+    req_str = struct.pack("HI", dev_id, dev_opt)
+    print("Set scan type %r to bluetooth device %d" % (scan_type, dev_id))
+    try:
+        fcntl.ioctl(hci_sock.fileno(), bluez.HCISETSCAN, req_str)
+    finally:
+        hci_sock.close()
+
+
+def raw_packet_to_str(pkt):
+    """
+    Returns the string representation of a raw HCI packet.
+    """
+    if sys.version_info > (3, 0):
+        return ''.join('%02x' % struct.unpack("B", bytes([x]))[0] for x in pkt)
+    else:
+        return ''.join('%02x' % struct.unpack("B", x)[0] for x in pkt)
+
+
+def enable_le_scan(sock, interval=0x0800, window=0x0800,
+                   filter_policy=FILTER_POLICY_NO_WHITELIST,
+                   filter_duplicates=True):
+    """
+    Enable LE passive scan (with filtering of duplicate packets enabled).
+
+    :param sock: A bluetooth HCI socket (retrieved using the
+        ``hci_open_dev`` PyBluez function).
+    :param interval: Scan interval.
+    :param window: Scan window (must be less or equal than given interval).
+    :param filter_policy: One of
+        ``FILTER_POLICY_NO_WHITELIST`` (default value)
+        ``FILTER_POLICY_SCAN_WHITELIST``
+        ``FILTER_POLICY_CONN_WHITELIST``
+        ``FILTER_POLICY_SCAN_AND_CONN_WHITELIST``
+
+    .. note:: Scan interval and window are to multiply by 0.625 ms to
+        get the real time duration.
+    """
+    print("Enable LE scan")
+    own_bdaddr_type = LE_PUBLIC_ADDRESS  # does not work with LE_RANDOM_ADDRESS
+    cmd_pkt = struct.pack("<BHHBB", SCAN_TYPE_PASSIVE, interval, window,
+                          own_bdaddr_type, filter_policy)
+    bluez.hci_send_cmd(sock, OGF_LE_CTL, OCF_LE_SET_SCAN_PARAMETERS, cmd_pkt)
+    print("scan params: interval=%.3fms window=%.3fms own_bdaddr=%s "
+          "whitelist=%s" %
+          (interval * 0.625, window * 0.625,
+           'public' if own_bdaddr_type == LE_PUBLIC_ADDRESS else 'random',
+           'yes' if filter_policy in (FILTER_POLICY_SCAN_WHITELIST,
+                                      FILTER_POLICY_SCAN_AND_CONN_WHITELIST)
+           else 'no'))
+    cmd_pkt = struct.pack("<BB", SCAN_ENABLE, SCAN_FILTER_DUPLICATES if filter_duplicates else 0x00)
+    bluez.hci_send_cmd(sock, OGF_LE_CTL, OCF_LE_SET_SCAN_ENABLE, cmd_pkt)
+
+
+def disable_le_scan(sock):
+    """
+    Disable LE scan.
+
+    :param sock: A bluetooth HCI socket (retrieved using the
+        ``hci_open_dev`` PyBluez function).
+    """
+    print("Disable LE scan")
+    cmd_pkt = struct.pack("<BB", SCAN_DISABLE, 0x00)
+    bluez.hci_send_cmd(sock, OGF_LE_CTL, OCF_LE_SET_SCAN_ENABLE, cmd_pkt)
+
+
+def start_le_advertising(sock, min_interval=1000, max_interval=1000,
+                         adv_type=ADV_NONCONN_IND, data=()):
+    """
+    Start LE advertising.
+
+    :param sock: A bluetooth HCI socket (retrieved using the
+        ``hci_open_dev`` PyBluez function).
+    :param min_interval: Minimum advertising interval.
+    :param max_interval: Maximum advertising interval.
+    :param adv_type: Advertisement type (``ADV_NONCONN_IND`` by default).
+    :param data: The advertisement data (maximum of 31 bytes).
+    :type data: iterable
+    """
+    own_bdaddr_type = 0
+    direct_bdaddr_type = 0
+    direct_bdaddr = (0,) * 6
+    chan_map = 0x07  # All channels: 37, 38, 39
+    filter = 0
+
+    struct_params = [min_interval, max_interval, adv_type, own_bdaddr_type,
+                     direct_bdaddr_type]
+    struct_params.extend(direct_bdaddr)
+    struct_params.extend((chan_map, filter))
+
+    cmd_pkt = struct.pack("<HHBBB6BBB", *struct_params)
+    bluez.hci_send_cmd(sock, OGF_LE_CTL, OCF_LE_SET_ADVERTISING_PARAMETERS,
+                       cmd_pkt)
+
+    cmd_pkt = struct.pack("<B", 0x01)
+    bluez.hci_send_cmd(sock, OGF_LE_CTL, OCF_LE_SET_ADVERTISE_ENABLE, cmd_pkt)
+
+    data_length = len(data)
+    if data_length > 31:
+        raise ValueError("data is too long (%d but max is 31 bytes)",
+                         data_length)
+    cmd_pkt = struct.pack("<B%dB" % data_length, data_length, *data)
+    bluez.hci_send_cmd(sock, OGF_LE_CTL, OCF_LE_SET_ADVERTISING_DATA, cmd_pkt)
+    print("Advertising started data_length=%d data=%r" % (data_length, data))
+
+
+def stop_le_advertising(sock):
+    """
+    Stop LE advertising.
+
+    :param sock: A bluetooth HCI socket (retrieved using the
+        ``hci_open_dev`` PyBluez function).
+    """
+    cmd_pkt = struct.pack("<B", 0x00)
+    bluez.hci_send_cmd(sock, OGF_LE_CTL, OCF_LE_SET_ADVERTISE_ENABLE, cmd_pkt)
+    print("Advertising stopped")
+
+
+def parse_le_advertising_events(sock, mac_addr=None, packet_length=None,
+                                handler=None, debug=False):
+    """
+    Parse and report LE advertisements.
+
+    This is a blocking call, an infinite loop is started and the
+    given handler will be called each time a new LE advertisement packet
+    is detected and corresponds to the given filters.
+
+    .. note:: The :func:`.start_le_advertising` function must be
+        called before calling this function.
+
+    :param sock: A bluetooth HCI socket (retrieved using the
+        ``hci_open_dev`` PyBluez function).
+    :param mac_addr: list of filtered mac address representations
+        (uppercase, with ':' separators).
+        If not specified, the LE advertisement of any device will be reported.
+        Example: mac_addr=('00:2A:5F:FF:25:11', 'DA:FF:12:33:66:12')
+    :type mac_addr: ``list`` of ``string``
+    :param packet_length: Filter a specific length of LE advertisement packet.
+    :type packet_length: ``int``
+    :param handler: Handler that will be called each time a LE advertisement
+        packet is available (in accordance with the ``mac_addr``
+        and ``packet_length`` filters).
+    :type handler: ``callable`` taking 4 parameters:
+        mac (``str``), adv_type (``int``), data (``bytes``) and rssi (``int``)
+    :param debug: Enable debug prints.
+    :type debug: ``bool``
+    """
+    if not debug and handler is None:
+        raise ValueError("You must either enable debug or give a handler !")
+
+    old_filter = sock.getsockopt(bluez.SOL_HCI, bluez.HCI_FILTER, 14)
+
+    flt = bluez.hci_filter_new()
+    bluez.hci_filter_set_ptype(flt, bluez.HCI_EVENT_PKT)
+    # bluez.hci_filter_all_events(flt)
+    bluez.hci_filter_set_event(flt, LE_META_EVENT)
+    sock.setsockopt(bluez.SOL_HCI, bluez.HCI_FILTER, flt)
+
+    print("socket filter set to ptype=HCI_EVENT_PKT event=LE_META_EVENT")
+    print("Listening ...")
+
+    try:
+        while True:
+            pkt = full_pkt = sock.recv(255)
+            ptype, event, plen = struct.unpack("BBB", pkt[:3])
+
+            if event != LE_META_EVENT:
+                # Should never occur because we filtered with this type of event
+                print("Not a LE_META_EVENT !")
+                continue
+
+            sub_event, = struct.unpack("B", pkt[3:4])
+            if sub_event != EVT_LE_ADVERTISING_REPORT:
+                if debug:
+                    print("Not a EVT_LE_ADVERTISING_REPORT !")
+                continue
+
+            pkt = pkt[4:]
+            adv_type = struct.unpack("b", pkt[1:2])[0]
+            mac_addr_str = bluez.ba2str(pkt[3:9])
+
+            if packet_length and plen != packet_length:
+                # ignore this packet
+                if debug:
+                    print("packet with non-matching length: mac=%s adv_type=%02x plen=%s" %
+                          (mac_addr_str, adv_type, plen))
+                    print(raw_packet_to_str(pkt))
+                continue
+
+            data = pkt[9:-1]
+
+            rssi = struct.unpack("b", full_pkt[len(full_pkt)-1:len(full_pkt)])[0]
+
+            if mac_addr and mac_addr_str not in mac_addr:
+                if debug:
+                    print("packet with non-matching mac %s adv_type=%02x data=%s RSSI=%s" %
+                          (mac_addr_str, adv_type, raw_packet_to_str(data), rssi))
+                continue
+
+            if debug:
+                print("LE advertisement: mac=%s adv_type=%02x data=%s RSSI=%d" %
+                      (mac_addr_str, adv_type, raw_packet_to_str(data), rssi))
+
+            if handler is not None:
+                try:
+                    handler(mac_addr_str, adv_type, data, rssi)
+                except Exception as e:
+                    print('Exception when calling handler with a BLE advertising event: %r' % (e,))
+                    import traceback
+                    traceback.print_exc()
+
+    except KeyboardInterrupt:
+        print("\nRestore previous socket filter")
+        sock.setsockopt(bluez.SOL_HCI, bluez.HCI_FILTER, old_filter)
+        raise
+
+"""
+def hci_le_add_white_list(int dd, const bdaddr_t *bdaddr, uint8_t type, int to)
+{
+    struct hci_request {
+        uint16_t ogf;
+        uint16_t ocf;
+        int      event;
+        void     *cparam;
+        int      clen;
+        void     *rparam;
+        int      rlen;
+    };
+
+    struct hci_request rq;
+    le_add_device_to_white_list_cp cp;
+    uint8_t status;
+
+    memset(&cp, 0, sizeof(cp));
+    cp.bdaddr_type = type;
+    bacpy(&cp.bdaddr, bdaddr);
+
+    memset(&rq, 0, sizeof(rq));
+    rq.ogf = OGF_LE_CTL;
+    rq.ocf = OCF_LE_ADD_DEVICE_TO_WHITE_LIST;
+    rq.cparam = &cp;
+    rq.clen = LE_ADD_DEVICE_TO_WHITE_LIST_CP_SIZE;
+    rq.rparam = &status;
+    rq.rlen = 1;
+
+    if (hci_send_req(dd, &rq, to) < 0)
+            return -1;
+
+    if (status) {
+            errno = EIO;
+            return -1;
+    }
+
+    return 0;
+}"""