Add:

- db cache dump on diagnostics request.
- individual device logs, db and files.
-Device logs api endpoints and diagnostics UI.

Fix:
- slmm standalone now uses local TZ (was UTC only before)
- fixed measurement start time logic.

app/background_poller.py

@@ -15,7 +15,8 @@ from sqlalchemy.orm import Session
 
 from app.database import SessionLocal
 from app.models import NL43Config, NL43Status
-from app.services import NL43Client, persist_snapshot
+from app.services import NL43Client, persist_snapshot, sync_measurement_start_time_from_ftp
+from app.device_logger import log_device_event, cleanup_old_logs
 
 logger = logging.getLogger(__name__)
 
@@ -25,7 +26,7 @@ class BackgroundPoller:
     Background task that continuously polls NL43 devices and updates status cache.
 
     Features:
-    - Per-device configurable poll intervals (10-3600 seconds)
+    - Per-device configurable poll intervals (30 seconds to 6 hours)
     - Automatic offline detection (marks unreachable after 3 consecutive failures)
     - Dynamic sleep intervals based on device configurations
     - Graceful shutdown on application stop
@@ -36,6 +37,7 @@ class BackgroundPoller:
         self._task: Optional[asyncio.Task] = None
         self._running = False
         self._logger = logger
+        self._last_cleanup = None  # Track last log cleanup time
 
     async def start(self):
         """Start the background polling task."""
@@ -78,6 +80,15 @@ class BackgroundPoller:
             except Exception as e:
                 self._logger.error(f"Error in poll loop: {e}", exc_info=True)
 
+            # Run log cleanup once per hour
+            try:
+                now = datetime.utcnow()
+                if self._last_cleanup is None or (now - self._last_cleanup).total_seconds() > 3600:
+                    cleanup_old_logs()
+                    self._last_cleanup = now
+            except Exception as e:
+                self._logger.warning(f"Log cleanup failed: {e}")
+
             # Calculate dynamic sleep interval
             sleep_time = self._calculate_sleep_interval()
             self._logger.debug(f"Sleeping for {sleep_time} seconds until next poll cycle")
@@ -205,6 +216,71 @@ class BackgroundPoller:
             db.commit()
             self._logger.info(f"✓ Successfully polled {unit_id}")
 
+            # Log to device log
+            log_device_event(
+                unit_id, "INFO", "POLL",
+                f"Poll success: state={snap.measurement_state}, Leq={snap.leq}, Lp={snap.lp}",
+                db
+            )
+
+            # Check if device is measuring but has no start time recorded
+            # This happens if measurement was started before SLMM began polling
+            # or after a service restart
+            status = db.query(NL43Status).filter_by(unit_id=unit_id).first()
+
+            # Reset the sync flag when measurement stops (so next measurement can sync)
+            if status and status.measurement_state != "Start":
+                if status.start_time_sync_attempted:
+                    status.start_time_sync_attempted = False
+                    db.commit()
+                    self._logger.debug(f"Reset FTP sync flag for {unit_id} (measurement stopped)")
+                    log_device_event(unit_id, "DEBUG", "STATE", "Measurement stopped, reset FTP sync flag", db)
+
+            # Attempt FTP sync if:
+            # - Device is measuring
+            # - No start time recorded
+            # - FTP sync not already attempted for this measurement
+            # - FTP is configured
+            if (status and
+                status.measurement_state == "Start" and
+                status.measurement_start_time is None and
+                not status.start_time_sync_attempted and
+                cfg.ftp_enabled and
+                cfg.ftp_username and
+                cfg.ftp_password):
+
+                self._logger.info(
+                    f"Device {unit_id} is measuring but has no start time - "
+                    f"attempting FTP sync"
+                )
+                log_device_event(unit_id, "INFO", "SYNC", "Attempting FTP sync for measurement start time", db)
+
+                # Mark that we attempted sync (prevents repeated attempts on failure)
+                status.start_time_sync_attempted = True
+                db.commit()
+
+                try:
+                    synced = await sync_measurement_start_time_from_ftp(
+                        unit_id=unit_id,
+                        host=cfg.host,
+                        tcp_port=cfg.tcp_port,
+                        ftp_port=cfg.ftp_port or 21,
+                        ftp_username=cfg.ftp_username,
+                        ftp_password=cfg.ftp_password,
+                        db=db
+                    )
+                    if synced:
+                        self._logger.info(f"✓ FTP sync succeeded for {unit_id}")
+                        log_device_event(unit_id, "INFO", "SYNC", "FTP sync succeeded - measurement start time updated", db)
+                    else:
+                        self._logger.warning(f"FTP sync returned False for {unit_id}")
+                        log_device_event(unit_id, "WARNING", "SYNC", "FTP sync returned False", db)
+                except Exception as sync_err:
+                    self._logger.warning(
+                        f"FTP sync failed for {unit_id}: {sync_err}"
+                    )
+                    log_device_event(unit_id, "ERROR", "SYNC", f"FTP sync failed: {sync_err}", db)
+
         except Exception as e:
             # Failure - increment counter and potentially mark offline
             status.consecutive_failures += 1
@@ -217,11 +293,13 @@ class BackgroundPoller:
                     self._logger.warning(
                         f"Device {unit_id} marked unreachable after {status.consecutive_failures} failures: {error_msg}"
                     )
+                    log_device_event(unit_id, "ERROR", "POLL", f"Device marked UNREACHABLE after {status.consecutive_failures} failures: {error_msg}", db)
                 status.is_reachable = False
             else:
                 self._logger.warning(
                     f"Poll failed for {unit_id} (attempt {status.consecutive_failures}/3): {error_msg}"
                 )
+                log_device_event(unit_id, "WARNING", "POLL", f"Poll failed (attempt {status.consecutive_failures}/3): {error_msg}", db)
 
             db.commit()
 
@@ -230,8 +308,8 @@ class BackgroundPoller:
         Calculate the next sleep interval based on all device poll intervals.
 
         Returns a dynamic sleep time that ensures responsive polling:
-        - Minimum 10 seconds (prevents tight loops)
+        - Minimum 30 seconds (prevents tight loops)
-        - Maximum 30 seconds (ensures responsiveness)
+        - Maximum 300 seconds / 5 minutes (ensures reasonable responsiveness for long intervals)
         - Generally half the minimum device interval
 
         Returns:
@@ -245,14 +323,15 @@ class BackgroundPoller:
             ).all()
 
             if not configs:
-                return 30  # Default sleep when no devices configured
+                return 60  # Default sleep when no devices configured
 
             # Get all intervals
             intervals = [cfg.poll_interval_seconds or 60 for cfg in configs]
             min_interval = min(intervals)
 
-            # Use half the minimum interval, but cap between 10-30 seconds
+            # Use half the minimum interval, but cap between 30-300 seconds
-            sleep_time = max(10, min(30, min_interval // 2))
+            # This allows longer sleep times when polling intervals are long (e.g., hourly)
+            sleep_time = max(30, min(300, min_interval // 2))
 
             return sleep_time
 

app/device_logger.py

@@ -0,0 +1,277 @@
+"""
+Per-device logging system.
+
+Provides dual output: database entries for structured queries and file logs for backup.
+Each device gets its own log file in data/logs/{unit_id}.log with rotation.
+"""
+
+import logging
+import os
+from datetime import datetime, timedelta
+from logging.handlers import RotatingFileHandler
+from pathlib import Path
+from typing import Optional
+
+from sqlalchemy.orm import Session
+
+from app.database import SessionLocal
+from app.models import DeviceLog
+
+# Configure base logger
+logger = logging.getLogger(__name__)
+
+# Log directory (persisted in Docker volume)
+LOG_DIR = Path(os.path.dirname(os.path.dirname(__file__))) / "data" / "logs"
+LOG_DIR.mkdir(parents=True, exist_ok=True)
+
+# Per-device file loggers (cached)
+_device_file_loggers: dict = {}
+
+# Log retention (days)
+LOG_RETENTION_DAYS = int(os.getenv("LOG_RETENTION_DAYS", "7"))
+
+
+def _get_file_logger(unit_id: str) -> logging.Logger:
+    """Get or create a file logger for a specific device."""
+    if unit_id in _device_file_loggers:
+        return _device_file_loggers[unit_id]
+
+    # Create device-specific logger
+    device_logger = logging.getLogger(f"device.{unit_id}")
+    device_logger.setLevel(logging.DEBUG)
+
+    # Avoid duplicate handlers
+    if not device_logger.handlers:
+        # Create rotating file handler (5 MB max, keep 3 backups)
+        log_file = LOG_DIR / f"{unit_id}.log"
+        handler = RotatingFileHandler(
+            log_file,
+            maxBytes=5 * 1024 * 1024,  # 5 MB
+            backupCount=3,
+            encoding="utf-8"
+        )
+        handler.setLevel(logging.DEBUG)
+
+        # Format: timestamp [LEVEL] [CATEGORY] message
+        formatter = logging.Formatter(
+            "%(asctime)s [%(levelname)s] [%(category)s] %(message)s",
+            datefmt="%Y-%m-%d %H:%M:%S"
+        )
+        handler.setFormatter(formatter)
+        device_logger.addHandler(handler)
+
+        # Don't propagate to root logger
+        device_logger.propagate = False
+
+    _device_file_loggers[unit_id] = device_logger
+    return device_logger
+
+
+def log_device_event(
+    unit_id: str,
+    level: str,
+    category: str,
+    message: str,
+    db: Optional[Session] = None
+):
+    """
+    Log an event for a specific device.
+
+    Writes to both:
+    1. Database (DeviceLog table) for structured queries
+    2. File (data/logs/{unit_id}.log) for backup/debugging
+
+    Args:
+        unit_id: Device identifier
+        level: Log level (DEBUG, INFO, WARNING, ERROR)
+        category: Event category (TCP, FTP, POLL, COMMAND, STATE, SYNC)
+        message: Log message
+        db: Optional database session (creates one if not provided)
+    """
+    timestamp = datetime.utcnow()
+
+    # Write to file log
+    try:
+        file_logger = _get_file_logger(unit_id)
+        log_func = getattr(file_logger, level.lower(), file_logger.info)
+        # Pass category as extra for formatter
+        log_func(message, extra={"category": category})
+    except Exception as e:
+        logger.warning(f"Failed to write file log for {unit_id}: {e}")
+
+    # Write to database
+    close_db = False
+    try:
+        if db is None:
+            db = SessionLocal()
+            close_db = True
+
+        log_entry = DeviceLog(
+            unit_id=unit_id,
+            timestamp=timestamp,
+            level=level.upper(),
+            category=category.upper(),
+            message=message
+        )
+        db.add(log_entry)
+        db.commit()
+
+    except Exception as e:
+        logger.warning(f"Failed to write DB log for {unit_id}: {e}")
+        if db:
+            db.rollback()
+    finally:
+        if close_db and db:
+            db.close()
+
+
+def cleanup_old_logs(retention_days: Optional[int] = None, db: Optional[Session] = None):
+    """
+    Delete log entries older than retention period.
+
+    Args:
+        retention_days: Days to retain (default: LOG_RETENTION_DAYS env var or 7)
+        db: Optional database session
+    """
+    if retention_days is None:
+        retention_days = LOG_RETENTION_DAYS
+
+    cutoff = datetime.utcnow() - timedelta(days=retention_days)
+
+    close_db = False
+    try:
+        if db is None:
+            db = SessionLocal()
+            close_db = True
+
+        deleted = db.query(DeviceLog).filter(DeviceLog.timestamp < cutoff).delete()
+        db.commit()
+
+        if deleted > 0:
+            logger.info(f"Cleaned up {deleted} log entries older than {retention_days} days")
+
+    except Exception as e:
+        logger.error(f"Failed to cleanup old logs: {e}")
+        if db:
+            db.rollback()
+    finally:
+        if close_db and db:
+            db.close()
+
+
+def get_device_logs(
+    unit_id: str,
+    limit: int = 100,
+    offset: int = 0,
+    level: Optional[str] = None,
+    category: Optional[str] = None,
+    since: Optional[datetime] = None,
+    db: Optional[Session] = None
+) -> list:
+    """
+    Query log entries for a specific device.
+
+    Args:
+        unit_id: Device identifier
+        limit: Max entries to return (default: 100)
+        offset: Number of entries to skip (default: 0)
+        level: Filter by level (DEBUG, INFO, WARNING, ERROR)
+        category: Filter by category (TCP, FTP, POLL, COMMAND, STATE, SYNC)
+        since: Filter entries after this timestamp
+        db: Optional database session
+
+    Returns:
+        List of log entries as dicts
+    """
+    close_db = False
+    try:
+        if db is None:
+            db = SessionLocal()
+            close_db = True
+
+        query = db.query(DeviceLog).filter(DeviceLog.unit_id == unit_id)
+
+        if level:
+            query = query.filter(DeviceLog.level == level.upper())
+        if category:
+            query = query.filter(DeviceLog.category == category.upper())
+        if since:
+            query = query.filter(DeviceLog.timestamp >= since)
+
+        # Order by newest first
+        query = query.order_by(DeviceLog.timestamp.desc())
+
+        # Apply pagination
+        entries = query.offset(offset).limit(limit).all()
+
+        return [
+            {
+                "id": e.id,
+                "timestamp": e.timestamp.isoformat() + "Z",
+                "level": e.level,
+                "category": e.category,
+                "message": e.message
+            }
+            for e in entries
+        ]
+
+    finally:
+        if close_db and db:
+            db.close()
+
+
+def get_log_stats(unit_id: str, db: Optional[Session] = None) -> dict:
+    """
+    Get log statistics for a device.
+
+    Returns:
+        Dict with counts by level and category
+    """
+    close_db = False
+    try:
+        if db is None:
+            db = SessionLocal()
+            close_db = True
+
+        total = db.query(DeviceLog).filter(DeviceLog.unit_id == unit_id).count()
+
+        # Count by level
+        level_counts = {}
+        for level in ["DEBUG", "INFO", "WARNING", "ERROR"]:
+            count = db.query(DeviceLog).filter(
+                DeviceLog.unit_id == unit_id,
+                DeviceLog.level == level
+            ).count()
+            if count > 0:
+                level_counts[level] = count
+
+        # Count by category
+        category_counts = {}
+        for category in ["TCP", "FTP", "POLL", "COMMAND", "STATE", "SYNC", "GENERAL"]:
+            count = db.query(DeviceLog).filter(
+                DeviceLog.unit_id == unit_id,
+                DeviceLog.category == category
+            ).count()
+            if count > 0:
+                category_counts[category] = count
+
+        # Get oldest and newest
+        oldest = db.query(DeviceLog).filter(
+            DeviceLog.unit_id == unit_id
+        ).order_by(DeviceLog.timestamp.asc()).first()
+
+        newest = db.query(DeviceLog).filter(
+            DeviceLog.unit_id == unit_id
+        ).order_by(DeviceLog.timestamp.desc()).first()
+
+        return {
+            "total": total,
+            "by_level": level_counts,
+            "by_category": category_counts,
+            "oldest": oldest.timestamp.isoformat() + "Z" if oldest else None,
+            "newest": newest.timestamp.isoformat() + "Z" if newest else None
+        }
+
+    finally:
+        if close_db and db:
+            db.close()

app/models.py

@@ -53,3 +53,22 @@ class NL43Status(Base):
     last_poll_attempt = Column(DateTime, nullable=True)  # Last time background poller attempted to poll
     last_success = Column(DateTime, nullable=True)  # Last successful poll timestamp
     last_error = Column(Text, nullable=True)  # Last error message (truncated to 500 chars)
+
+    # FTP start time sync tracking
+    start_time_sync_attempted = Column(Boolean, default=False)  # True if FTP sync was attempted for current measurement
+
+
+class DeviceLog(Base):
+    """
+    Per-device log entries for debugging and audit trail.
+    Stores events like commands, state changes, errors, and FTP operations.
+    """
+
+    __tablename__ = "device_logs"
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    unit_id = Column(String, index=True, nullable=False)
+    timestamp = Column(DateTime, default=func.now(), index=True)
+    level = Column(String, default="INFO")  # DEBUG, INFO, WARNING, ERROR
+    category = Column(String, default="GENERAL")  # TCP, FTP, POLL, COMMAND, STATE, SYNC
+    message = Column(Text, nullable=False)

app/routers.py

@@ -3,6 +3,7 @@ from fastapi.responses import FileResponse
 from sqlalchemy.orm import Session
 from datetime import datetime
 from pydantic import BaseModel, field_validator, Field
+from typing import Optional
 import logging
 import ipaddress
 import json
@@ -81,14 +82,14 @@ class ConfigPayload(BaseModel):
     @field_validator("poll_interval_seconds")
     @classmethod
     def validate_poll_interval(cls, v):
-        if v is not None and not (10 <= v <= 3600):
+        if v is not None and not (30 <= v <= 21600):
-            raise ValueError("Poll interval must be between 10 and 3600 seconds")
+            raise ValueError("Poll interval must be between 30 and 21600 seconds (30s to 6 hours)")
         return v
 
 
 class PollingConfigPayload(BaseModel):
     """Payload for updating device polling configuration."""
-    poll_interval_seconds: int | None = Field(None, ge=10, le=3600, description="Polling interval in seconds (10-3600)")
+    poll_interval_seconds: int | None = Field(None, ge=30, le=21600, description="Polling interval in seconds (30s to 6 hours)")
     poll_enabled: bool | None = Field(None, description="Enable or disable background polling for this device")
 
 
@@ -233,8 +234,8 @@ class RosterCreatePayload(BaseModel):
     @field_validator("poll_interval_seconds")
     @classmethod
     def validate_poll_interval(cls, v):
-        if v is not None and not (10 <= v <= 3600):
+        if v is not None and not (30 <= v <= 21600):
-            raise ValueError("Poll interval must be between 10 and 3600 seconds")
+            raise ValueError("Poll interval must be between 30 and 21600 seconds (30s to 6 hours)")
         return v
 
 
@@ -1842,9 +1843,134 @@ async def run_diagnostics(unit_id: str, db: Session = Depends(get_db)):
 
     # All tests passed
     diagnostics["overall_status"] = "pass"
+
+    # Add database dump: config and status cache
+    diagnostics["database_dump"] = {
+        "config": {
+            "unit_id": cfg.unit_id,
+            "host": cfg.host,
+            "tcp_port": cfg.tcp_port,
+            "tcp_enabled": cfg.tcp_enabled,
+            "ftp_enabled": cfg.ftp_enabled,
+            "ftp_port": cfg.ftp_port,
+            "ftp_username": cfg.ftp_username,
+            "ftp_password": "***" if cfg.ftp_password else None,  # Mask password
+            "web_enabled": cfg.web_enabled,
+            "poll_interval_seconds": cfg.poll_interval_seconds,
+            "poll_enabled": cfg.poll_enabled
+        },
+        "status_cache": None
+    }
+
+    # Get cached status if available
+    status = db.query(NL43Status).filter_by(unit_id=unit_id).first()
+    if status:
+        # Helper to format datetime as ISO with Z suffix to indicate UTC
+        def to_utc_iso(dt):
+            return dt.isoformat() + 'Z' if dt else None
+
+        diagnostics["database_dump"]["status_cache"] = {
+            "unit_id": status.unit_id,
+            "last_seen": to_utc_iso(status.last_seen),
+            "measurement_state": status.measurement_state,
+            "measurement_start_time": to_utc_iso(status.measurement_start_time),
+            "counter": status.counter,
+            "lp": status.lp,
+            "leq": status.leq,
+            "lmax": status.lmax,
+            "lmin": status.lmin,
+            "lpeak": status.lpeak,
+            "battery_level": status.battery_level,
+            "power_source": status.power_source,
+            "sd_remaining_mb": status.sd_remaining_mb,
+            "sd_free_ratio": status.sd_free_ratio,
+            "is_reachable": status.is_reachable,
+            "consecutive_failures": status.consecutive_failures,
+            "last_poll_attempt": to_utc_iso(status.last_poll_attempt),
+            "last_success": to_utc_iso(status.last_success),
+            "last_error": status.last_error,
+            "raw_payload": status.raw_payload
+        }
+
     return diagnostics
 
 
+# ============================================================================
+# DEVICE LOGS ENDPOINTS
+# ============================================================================
+
+@router.get("/{unit_id}/logs")
+def get_device_logs(
+    unit_id: str,
+    limit: int = 100,
+    offset: int = 0,
+    level: Optional[str] = None,
+    category: Optional[str] = None,
+    db: Session = Depends(get_db)
+):
+    """
+    Get log entries for a specific device.
+
+    Query parameters:
+    - limit: Max entries to return (default: 100, max: 1000)
+    - offset: Number of entries to skip (for pagination)
+    - level: Filter by level (DEBUG, INFO, WARNING, ERROR)
+    - category: Filter by category (TCP, FTP, POLL, COMMAND, STATE, SYNC)
+
+    Returns newest entries first.
+    """
+    from app.device_logger import get_device_logs as fetch_logs, get_log_stats
+
+    # Validate limit
+    limit = min(limit, 1000)
+
+    logs = fetch_logs(
+        unit_id=unit_id,
+        limit=limit,
+        offset=offset,
+        level=level,
+        category=category,
+        db=db
+    )
+
+    stats = get_log_stats(unit_id, db)
+
+    return {
+        "status": "ok",
+        "unit_id": unit_id,
+        "logs": logs,
+        "count": len(logs),
+        "stats": stats,
+        "filters": {
+            "level": level,
+            "category": category
+        },
+        "pagination": {
+            "limit": limit,
+            "offset": offset
+        }
+    }
+
+
+@router.delete("/{unit_id}/logs")
+def clear_device_logs(unit_id: str, db: Session = Depends(get_db)):
+    """
+    Clear all log entries for a specific device.
+    """
+    from app.models import DeviceLog
+
+    deleted = db.query(DeviceLog).filter(DeviceLog.unit_id == unit_id).delete()
+    db.commit()
+
+    logger.info(f"Cleared {deleted} log entries for device {unit_id}")
+
+    return {
+        "status": "ok",
+        "message": f"Cleared {deleted} log entries for {unit_id}",
+        "deleted_count": deleted
+    }
+
+
 # ============================================================================
 # BACKGROUND POLLING CONFIGURATION ENDPOINTS
 # ============================================================================
@@ -1880,7 +2006,7 @@ def update_polling_config(
     """
     Update background polling configuration for a device.
 
-    Allows configuring the polling interval (10-3600 seconds) and
+    Allows configuring the polling interval (30-21600 seconds, i.e. 30s to 6 hours) and
     enabling/disabling automatic background polling per device.
 
     Changes take effect on the next polling cycle.
@@ -1891,10 +2017,15 @@ def update_polling_config(
 
     # Update interval if provided
     if payload.poll_interval_seconds is not None:
-        if payload.poll_interval_seconds < 10:
+        if payload.poll_interval_seconds < 30:
             raise HTTPException(
                 status_code=400,
-                detail="Polling interval must be at least 10 seconds"
+                detail="Polling interval must be at least 30 seconds"
+            )
+        if payload.poll_interval_seconds > 21600:
+            raise HTTPException(
+                status_code=400,
+                detail="Polling interval must be at most 21600 seconds (6 hours)"
             )
         cfg.poll_interval_seconds = payload.poll_interval_seconds
 

app/services.py

@@ -14,7 +14,7 @@ import zipfile
 import tempfile
 from dataclasses import dataclass
 from datetime import datetime, timezone, timedelta
-from typing import Optional, List
+from typing import Optional, List, Dict
 from sqlalchemy.orm import Session
 from ftplib import FTP
 from pathlib import Path
@@ -76,10 +76,22 @@ def persist_snapshot(s: NL43Snapshot, db: Session):
             # Measurement just started - record the start time
             row.measurement_start_time = datetime.utcnow()
             logger.info(f"✓ Measurement started on {s.unit_id} at {row.measurement_start_time}")
+            # Log state change (lazy import to avoid circular dependency)
+            try:
+                from app.device_logger import log_device_event
+                log_device_event(s.unit_id, "INFO", "STATE", f"Measurement STARTED at {row.measurement_start_time}", db)
+            except Exception:
+                pass
         elif was_measuring and not is_measuring:
             # Measurement stopped - clear the start time
             row.measurement_start_time = None
             logger.info(f"✓ Measurement stopped on {s.unit_id}")
+            # Log state change
+            try:
+                from app.device_logger import log_device_event
+                log_device_event(s.unit_id, "INFO", "STATE", "Measurement STOPPED", db)
+            except Exception:
+                pass
 
         row.measurement_state = new_state
         row.counter = s.counter
@@ -101,10 +113,126 @@ def persist_snapshot(s: NL43Snapshot, db: Session):
         raise
 
 
+async def sync_measurement_start_time_from_ftp(
+    unit_id: str,
+    host: str,
+    tcp_port: int,
+    ftp_port: int,
+    ftp_username: str,
+    ftp_password: str,
+    db: Session
+) -> bool:
+    """
+    Sync measurement start time from the FTP folder timestamp.
+
+    This is called when SLMM detects a device is already measuring but doesn't
+    have a recorded start time (e.g., after service restart or if measurement
+    was started before SLMM began polling).
+
+    The workflow:
+    1. Disable FTP (reset)
+    2. Enable FTP
+    3. List NL-43 folder to get measurement folder timestamps
+    4. Use the most recent folder's timestamp as the start time
+    5. Update the database
+
+    Args:
+        unit_id: Device identifier
+        host: Device IP/hostname
+        tcp_port: TCP control port
+        ftp_port: FTP port (usually 21)
+        ftp_username: FTP username (usually "USER")
+        ftp_password: FTP password (usually "0000")
+        db: Database session
+
+    Returns:
+        True if sync succeeded, False otherwise
+    """
+    logger.info(f"[FTP-SYNC] Attempting to sync measurement start time for {unit_id} via FTP")
+
+    client = NL43Client(
+        host, tcp_port,
+        ftp_username=ftp_username,
+        ftp_password=ftp_password,
+        ftp_port=ftp_port
+    )
+
+    try:
+        # Step 1: Disable FTP to reset it
+        logger.info(f"[FTP-SYNC] Step 1: Disabling FTP on {unit_id}")
+        await client.disable_ftp()
+        await asyncio.sleep(1.5)  # Wait for device to process
+
+        # Step 2: Enable FTP
+        logger.info(f"[FTP-SYNC] Step 2: Enabling FTP on {unit_id}")
+        await client.enable_ftp()
+        await asyncio.sleep(2.0)  # Wait for FTP server to start
+
+        # Step 3: List NL-43 folder
+        logger.info(f"[FTP-SYNC] Step 3: Listing /NL-43 folder on {unit_id}")
+        files = await client.list_ftp_files("/NL-43")
+
+        # Filter for directories only (measurement folders)
+        folders = [f for f in files if f.get('is_dir', False)]
+
+        if not folders:
+            logger.warning(f"[FTP-SYNC] No measurement folders found on {unit_id}")
+            return False
+
+        # Sort by modified timestamp (newest first)
+        folders.sort(key=lambda f: f.get('modified_timestamp', ''), reverse=True)
+
+        latest_folder = folders[0]
+        folder_name = latest_folder['name']
+        logger.info(f"[FTP-SYNC] Found latest measurement folder: {folder_name}")
+
+        # Step 4: Parse timestamp
+        if 'modified_timestamp' in latest_folder and latest_folder['modified_timestamp']:
+            timestamp_str = latest_folder['modified_timestamp']
+            # Parse ISO format timestamp (already in UTC from SLMM FTP listing)
+            start_time = datetime.fromisoformat(timestamp_str.replace('Z', ''))
+
+            # Step 5: Update database
+            status = db.query(NL43Status).filter_by(unit_id=unit_id).first()
+            if status:
+                old_time = status.measurement_start_time
+                status.measurement_start_time = start_time
+                db.commit()
+
+                logger.info(f"[FTP-SYNC] ✓ Successfully synced start time for {unit_id}")
+                logger.info(f"[FTP-SYNC]   Folder: {folder_name}")
+                logger.info(f"[FTP-SYNC]   Old start time: {old_time}")
+                logger.info(f"[FTP-SYNC]   New start time: {start_time}")
+                return True
+            else:
+                logger.warning(f"[FTP-SYNC] Status record not found for {unit_id}")
+                return False
+        else:
+            logger.warning(f"[FTP-SYNC] Could not parse timestamp from folder {folder_name}")
+            return False
+
+    except Exception as e:
+        logger.error(f"[FTP-SYNC] Failed to sync start time for {unit_id}: {e}")
+        return False
+
+
 # Rate limiting: NL43 requires ≥1 second between commands
 _last_command_time = {}
 _rate_limit_lock = asyncio.Lock()
 
+# Per-device connection locks: NL43 devices only support one TCP connection at a time
+# This prevents concurrent connections from fighting for the device
+_device_locks: Dict[str, asyncio.Lock] = {}
+_device_locks_lock = asyncio.Lock()
+
+
+async def _get_device_lock(device_key: str) -> asyncio.Lock:
+    """Get or create a lock for a specific device."""
+    async with _device_locks_lock:
+        if device_key not in _device_locks:
+            _device_locks[device_key] = asyncio.Lock()
+        return _device_locks[device_key]
+
 
 class NL43Client:
     def __init__(self, host: str, port: int, timeout: float = 5.0, ftp_username: str = None, ftp_password: str = None, ftp_port: int = 21):
@@ -133,7 +261,17 @@ class NL43Client:
         NL43 protocol returns two lines for query commands:
         Line 1: Result code (R+0000 for success, error codes otherwise)
         Line 2: Actual data (for query commands ending with '?')
+
+        This method acquires a per-device lock to ensure only one TCP connection
+        is active at a time (NL43 devices only support single connections).
         """
+        # Acquire per-device lock to prevent concurrent connections
+        device_lock = await _get_device_lock(self.device_key)
+        async with device_lock:
+            return await self._send_command_unlocked(cmd)
+
+    async def _send_command_unlocked(self, cmd: str) -> str:
+        """Internal: send command without acquiring device lock (lock must be held by caller)."""
         await self._enforce_rate_limit()
 
         logger.info(f"Sending command to {self.device_key}: {cmd.strip()}")
@@ -429,105 +567,112 @@ class NL43Client:
 
         The stream continues until an exception occurs or the connection is closed.
         Send SUB character (0x1A) to stop the stream.
+
+        NOTE: This method holds the device lock for the entire duration of streaming,
+        blocking other commands to this device. This is intentional since NL43 devices
+        only support one TCP connection at a time.
         """
-        await self._enforce_rate_limit()
+        # Acquire per-device lock - held for entire streaming session
+        device_lock = await _get_device_lock(self.device_key)
+        async with device_lock:
+            await self._enforce_rate_limit()
 
-        logger.info(f"Starting DRD stream for {self.device_key}")
+            logger.info(f"Starting DRD stream for {self.device_key}")
 
-        try:
-            reader, writer = await asyncio.wait_for(
-                asyncio.open_connection(self.host, self.port), timeout=self.timeout
-            )
-        except asyncio.TimeoutError:
-            logger.error(f"DRD stream connection timeout to {self.device_key}")
-            raise ConnectionError(f"Failed to connect to device at {self.host}:{self.port}")
-        except Exception as e:
-            logger.error(f"DRD stream connection failed to {self.device_key}: {e}")
-            raise ConnectionError(f"Failed to connect to device: {str(e)}")
-
-        try:
-            # Start DRD streaming
-            writer.write(b"DRD?\r\n")
-            await writer.drain()
-
-            # Read initial result code
-            first_line_data = await asyncio.wait_for(reader.readuntil(b"\n"), timeout=self.timeout)
-            result_code = first_line_data.decode(errors="ignore").strip()
-
-            if result_code.startswith("$"):
-                result_code = result_code[1:].strip()
-
-            logger.debug(f"DRD stream result code from {self.device_key}: {result_code}")
-
-            if result_code != "R+0000":
-                raise ValueError(f"DRD stream failed to start: {result_code}")
-
-            logger.info(f"DRD stream started successfully for {self.device_key}")
-
-            # Continuously read data lines
-            while True:
-                try:
-                    line_data = await asyncio.wait_for(reader.readuntil(b"\n"), timeout=30.0)
-                    line = line_data.decode(errors="ignore").strip()
-
-                    if not line:
-                        continue
-
-                    # Remove leading $ if present
-                    if line.startswith("$"):
-                        line = line[1:].strip()
-
-                    # Parse the DRD data (same format as DOD)
-                    parts = [p.strip() for p in line.split(",") if p.strip() != ""]
-
-                    if len(parts) < 2:
-                        logger.warning(f"Malformed DRD data from {self.device_key}: {line}")
-                        continue
-
-                    snap = NL43Snapshot(unit_id="", raw_payload=line, measurement_state="Measure")
-
-                    # Parse known positions (DRD format - same as DOD)
-                    # DRD format: d0=counter, d1=Lp, d2=Leq, d3=Lmax, d4=Lmin, d5=Lpeak, d6=LIeq, ...
-                    try:
-                        # Capture d0 (counter) for timer synchronization
-                        if len(parts) >= 1:
-                            snap.counter = parts[0]  # d0: Measurement interval counter (1-600)
-                        if len(parts) >= 2:
-                            snap.lp = parts[1]     # d1: Instantaneous sound pressure level
-                        if len(parts) >= 3:
-                            snap.leq = parts[2]    # d2: Equivalent continuous sound level
-                        if len(parts) >= 4:
-                            snap.lmax = parts[3]   # d3: Maximum level
-                        if len(parts) >= 5:
-                            snap.lmin = parts[4]   # d4: Minimum level
-                        if len(parts) >= 6:
-                            snap.lpeak = parts[5]  # d5: Peak level
-                    except (IndexError, ValueError) as e:
-                        logger.warning(f"Error parsing DRD data points: {e}")
-
-                    # Call the callback with the snapshot
-                    await callback(snap)
-
-                except asyncio.TimeoutError:
-                    logger.warning(f"DRD stream timeout (no data for 30s) from {self.device_key}")
-                    break
-                except asyncio.IncompleteReadError:
-                    logger.info(f"DRD stream closed by device {self.device_key}")
-                    break
-
-        finally:
-            # Send SUB character to stop streaming
             try:
-                writer.write(b"\x1A")
+                reader, writer = await asyncio.wait_for(
+                    asyncio.open_connection(self.host, self.port), timeout=self.timeout
+                )
+            except asyncio.TimeoutError:
+                logger.error(f"DRD stream connection timeout to {self.device_key}")
+                raise ConnectionError(f"Failed to connect to device at {self.host}:{self.port}")
+            except Exception as e:
+                logger.error(f"DRD stream connection failed to {self.device_key}: {e}")
+                raise ConnectionError(f"Failed to connect to device: {str(e)}")
+
+            try:
+                # Start DRD streaming
+                writer.write(b"DRD?\r\n")
                 await writer.drain()
-            except Exception:
-                pass
 
-            writer.close()
+                # Read initial result code
-            with contextlib.suppress(Exception):
+                first_line_data = await asyncio.wait_for(reader.readuntil(b"\n"), timeout=self.timeout)
-                await writer.wait_closed()
+                result_code = first_line_data.decode(errors="ignore").strip()
 
-            logger.info(f"DRD stream ended for {self.device_key}")
+                if result_code.startswith("$"):
+                    result_code = result_code[1:].strip()
+
+                logger.debug(f"DRD stream result code from {self.device_key}: {result_code}")
+
+                if result_code != "R+0000":
+                    raise ValueError(f"DRD stream failed to start: {result_code}")
+
+                logger.info(f"DRD stream started successfully for {self.device_key}")
+
+                # Continuously read data lines
+                while True:
+                    try:
+                        line_data = await asyncio.wait_for(reader.readuntil(b"\n"), timeout=30.0)
+                        line = line_data.decode(errors="ignore").strip()
+
+                        if not line:
+                            continue
+
+                        # Remove leading $ if present
+                        if line.startswith("$"):
+                            line = line[1:].strip()
+
+                        # Parse the DRD data (same format as DOD)
+                        parts = [p.strip() for p in line.split(",") if p.strip() != ""]
+
+                        if len(parts) < 2:
+                            logger.warning(f"Malformed DRD data from {self.device_key}: {line}")
+                            continue
+
+                        snap = NL43Snapshot(unit_id="", raw_payload=line, measurement_state="Measure")
+
+                        # Parse known positions (DRD format - same as DOD)
+                        # DRD format: d0=counter, d1=Lp, d2=Leq, d3=Lmax, d4=Lmin, d5=Lpeak, d6=LIeq, ...
+                        try:
+                            # Capture d0 (counter) for timer synchronization
+                            if len(parts) >= 1:
+                                snap.counter = parts[0]  # d0: Measurement interval counter (1-600)
+                            if len(parts) >= 2:
+                                snap.lp = parts[1]     # d1: Instantaneous sound pressure level
+                            if len(parts) >= 3:
+                                snap.leq = parts[2]    # d2: Equivalent continuous sound level
+                            if len(parts) >= 4:
+                                snap.lmax = parts[3]   # d3: Maximum level
+                            if len(parts) >= 5:
+                                snap.lmin = parts[4]   # d4: Minimum level
+                            if len(parts) >= 6:
+                                snap.lpeak = parts[5]  # d5: Peak level
+                        except (IndexError, ValueError) as e:
+                            logger.warning(f"Error parsing DRD data points: {e}")
+
+                        # Call the callback with the snapshot
+                        await callback(snap)
+
+                    except asyncio.TimeoutError:
+                        logger.warning(f"DRD stream timeout (no data for 30s) from {self.device_key}")
+                        break
+                    except asyncio.IncompleteReadError:
+                        logger.info(f"DRD stream closed by device {self.device_key}")
+                        break
+
+            finally:
+                # Send SUB character to stop streaming
+                try:
+                    writer.write(b"\x1A")
+                    await writer.drain()
+                except Exception:
+                    pass
+
+                writer.close()
+                with contextlib.suppress(Exception):
+                    await writer.wait_closed()
+
+                logger.info(f"DRD stream ended for {self.device_key}")
 
     async def set_measurement_time(self, preset: str):
         """Set measurement time preset.

migrate_add_device_logs.py

@@ -0,0 +1,73 @@
+#!/usr/bin/env python3
+"""
+Database migration: Add device_logs table.
+
+This table stores per-device log entries for debugging and audit trail.
+
+Run this once to add the new table.
+"""
+
+import sqlite3
+import os
+
+# Path to the SLMM database
+DB_PATH = os.path.join(os.path.dirname(__file__), "data", "slmm.db")
+
+
+def migrate():
+    print(f"Adding device_logs table to: {DB_PATH}")
+
+    if not os.path.exists(DB_PATH):
+        print("Database does not exist yet. Table will be created automatically on first run.")
+        return
+
+    conn = sqlite3.connect(DB_PATH)
+    cursor = conn.cursor()
+
+    try:
+        # Check if table already exists
+        cursor.execute("""
+            SELECT name FROM sqlite_master
+            WHERE type='table' AND name='device_logs'
+        """)
+        if cursor.fetchone():
+            print("✓ device_logs table already exists, no migration needed")
+            return
+
+        # Create the table
+        print("Creating device_logs table...")
+        cursor.execute("""
+            CREATE TABLE device_logs (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                unit_id VARCHAR NOT NULL,
+                timestamp DATETIME DEFAULT CURRENT_TIMESTAMP,
+                level VARCHAR DEFAULT 'INFO',
+                category VARCHAR DEFAULT 'GENERAL',
+                message TEXT NOT NULL
+            )
+        """)
+
+        # Create indexes for efficient querying
+        print("Creating indexes...")
+        cursor.execute("CREATE INDEX ix_device_logs_unit_id ON device_logs (unit_id)")
+        cursor.execute("CREATE INDEX ix_device_logs_timestamp ON device_logs (timestamp)")
+
+        conn.commit()
+        print("✓ Created device_logs table with indexes")
+
+        # Verify
+        cursor.execute("""
+            SELECT name FROM sqlite_master
+            WHERE type='table' AND name='device_logs'
+        """)
+        if not cursor.fetchone():
+            raise Exception("device_logs table was not created successfully")
+
+        print("✓ Migration completed successfully")
+
+    finally:
+        conn.close()
+
+
+if __name__ == "__main__":
+    migrate()

migrate_add_start_time_sync_flag.py

@@ -0,0 +1,60 @@
+#!/usr/bin/env python3
+"""
+Database migration: Add start_time_sync_attempted field to nl43_status table.
+
+This field tracks whether FTP sync has been attempted for the current measurement,
+preventing repeated sync attempts when FTP fails.
+
+Run this once to add the new column.
+"""
+
+import sqlite3
+import os
+
+# Path to the SLMM database
+DB_PATH = os.path.join(os.path.dirname(__file__), "data", "slmm.db")
+
+
+def migrate():
+    print(f"Adding start_time_sync_attempted field to: {DB_PATH}")
+
+    if not os.path.exists(DB_PATH):
+        print("Database does not exist yet. Column will be created automatically.")
+        return
+
+    conn = sqlite3.connect(DB_PATH)
+    cursor = conn.cursor()
+
+    try:
+        # Check if column already exists
+        cursor.execute("PRAGMA table_info(nl43_status)")
+        columns = [col[1] for col in cursor.fetchall()]
+
+        if 'start_time_sync_attempted' in columns:
+            print("✓ start_time_sync_attempted column already exists, no migration needed")
+            return
+
+        # Add the column
+        print("Adding start_time_sync_attempted column...")
+        cursor.execute("""
+            ALTER TABLE nl43_status
+            ADD COLUMN start_time_sync_attempted BOOLEAN DEFAULT 0
+        """)
+        conn.commit()
+        print("✓ Added start_time_sync_attempted column")
+
+        # Verify
+        cursor.execute("PRAGMA table_info(nl43_status)")
+        columns = [col[1] for col in cursor.fetchall()]
+
+        if 'start_time_sync_attempted' not in columns:
+            raise Exception("start_time_sync_attempted column was not added successfully")
+
+        print("✓ Migration completed successfully")
+
+    finally:
+        conn.close()
+
+
+if __name__ == "__main__":
+    migrate()

templates/index.html

@@ -333,6 +333,134 @@
 
         html += `<p style="margin-top: 12px; font-size: 0.9em; color: #666;">Last run: ${new Date(data.timestamp).toLocaleString()}</p>`;
 
+        // Add database dump section if available
+        if (data.database_dump) {
+          html += `<div style="margin-top: 16px; border-top: 1px solid #d0d7de; padding-top: 12px;">`;
+          html += `<h4 style="margin: 0 0 12px 0;">📦 Database Dump</h4>`;
+
+          // Config section
+          if (data.database_dump.config) {
+            const cfg = data.database_dump.config;
+            html += `<div style="background: #f0f4f8; padding: 12px; border-radius: 4px; margin-bottom: 12px;">`;
+            html += `<strong>Configuration (nl43_config)</strong>`;
+            html += `<table style="width: 100%; margin-top: 8px; font-size: 0.9em;">`;
+            html += `<tr><td style="padding: 2px 8px; color: #666;">Host</td><td>${cfg.host}:${cfg.tcp_port}</td></tr>`;
+            html += `<tr><td style="padding: 2px 8px; color: #666;">TCP Enabled</td><td>${cfg.tcp_enabled ? '✓' : '✗'}</td></tr>`;
+            html += `<tr><td style="padding: 2px 8px; color: #666;">FTP Enabled</td><td>${cfg.ftp_enabled ? '✓' : '✗'}${cfg.ftp_enabled ? ` (port ${cfg.ftp_port}, user: ${cfg.ftp_username || 'none'})` : ''}</td></tr>`;
+            html += `<tr><td style="padding: 2px 8px; color: #666;">Background Polling</td><td>${cfg.poll_enabled ? `✓ every ${cfg.poll_interval_seconds}s` : '✗ disabled'}</td></tr>`;
+            html += `</table></div>`;
+          }
+
+          // Status cache section
+          if (data.database_dump.status_cache) {
+            const cache = data.database_dump.status_cache;
+            html += `<div style="background: #f0f8f4; padding: 12px; border-radius: 4px; margin-bottom: 12px;">`;
+            html += `<strong>Status Cache (nl43_status)</strong>`;
+            html += `<table style="width: 100%; margin-top: 8px; font-size: 0.9em;">`;
+
+            // Measurement state and timing
+            html += `<tr><td style="padding: 2px 8px; color: #666;">Measurement State</td><td><strong>${cache.measurement_state || 'unknown'}</strong></td></tr>`;
+            if (cache.measurement_start_time) {
+              const startTime = new Date(cache.measurement_start_time);
+              const elapsed = Math.floor((Date.now() - startTime) / 1000);
+              const elapsedStr = elapsed > 3600 ? `${Math.floor(elapsed/3600)}h ${Math.floor((elapsed%3600)/60)}m` : elapsed > 60 ? `${Math.floor(elapsed/60)}m ${elapsed%60}s` : `${elapsed}s`;
+              html += `<tr><td style="padding: 2px 8px; color: #666;">Measurement Started</td><td>${startTime.toLocaleString()} (${elapsedStr} ago)</td></tr>`;
+            }
+            html += `<tr><td style="padding: 2px 8px; color: #666;">Counter (d0)</td><td>${cache.counter || 'N/A'}</td></tr>`;
+
+            // Sound levels
+            html += `<tr><td colspan="2" style="padding: 8px 8px 2px 8px; font-weight: 600; border-top: 1px solid #d0d7de;">Sound Levels (dB)</td></tr>`;
+            html += `<tr><td style="padding: 2px 8px; color: #666;">Lp (Instantaneous)</td><td>${cache.lp || 'N/A'}</td></tr>`;
+            html += `<tr><td style="padding: 2px 8px; color: #666;">Leq (Equivalent)</td><td>${cache.leq || 'N/A'}</td></tr>`;
+            html += `<tr><td style="padding: 2px 8px; color: #666;">Lmax / Lmin</td><td>${cache.lmax || 'N/A'} / ${cache.lmin || 'N/A'}</td></tr>`;
+            html += `<tr><td style="padding: 2px 8px; color: #666;">Lpeak</td><td>${cache.lpeak || 'N/A'}</td></tr>`;
+
+            // Device status
+            html += `<tr><td colspan="2" style="padding: 8px 8px 2px 8px; font-weight: 600; border-top: 1px solid #d0d7de;">Device Status</td></tr>`;
+            html += `<tr><td style="padding: 2px 8px; color: #666;">Battery</td><td>${cache.battery_level || 'N/A'}${cache.power_source ? ` (${cache.power_source})` : ''}</td></tr>`;
+            html += `<tr><td style="padding: 2px 8px; color: #666;">SD Card</td><td>${cache.sd_remaining_mb ? `${cache.sd_remaining_mb} MB` : 'N/A'}${cache.sd_free_ratio ? ` (${cache.sd_free_ratio} free)` : ''}</td></tr>`;
+
+            // Polling status
+            html += `<tr><td colspan="2" style="padding: 8px 8px 2px 8px; font-weight: 600; border-top: 1px solid #d0d7de;">Polling Status</td></tr>`;
+            html += `<tr><td style="padding: 2px 8px; color: #666;">Reachable</td><td>${cache.is_reachable ? '🟢 Yes' : '🔴 No'}</td></tr>`;
+            if (cache.last_seen) {
+              html += `<tr><td style="padding: 2px 8px; color: #666;">Last Seen</td><td>${new Date(cache.last_seen).toLocaleString()}</td></tr>`;
+            }
+            if (cache.last_success) {
+              html += `<tr><td style="padding: 2px 8px; color: #666;">Last Success</td><td>${new Date(cache.last_success).toLocaleString()}</td></tr>`;
+            }
+            if (cache.last_poll_attempt) {
+              html += `<tr><td style="padding: 2px 8px; color: #666;">Last Poll Attempt</td><td>${new Date(cache.last_poll_attempt).toLocaleString()}</td></tr>`;
+            }
+            html += `<tr><td style="padding: 2px 8px; color: #666;">Consecutive Failures</td><td>${cache.consecutive_failures || 0}</td></tr>`;
+            if (cache.last_error) {
+              html += `<tr><td style="padding: 2px 8px; color: #666;">Last Error</td><td style="color: #d00; font-size: 0.85em;">${cache.last_error}</td></tr>`;
+            }
+
+            html += `</table></div>`;
+
+            // Raw payload (collapsible)
+            if (cache.raw_payload) {
+              html += `<details style="margin-top: 8px;"><summary style="cursor: pointer; color: #666; font-size: 0.9em;">📄 Raw Payload</summary>`;
+              html += `<pre style="background: #f6f8fa; padding: 8px; border-radius: 4px; font-size: 0.8em; overflow-x: auto; margin-top: 8px;">${cache.raw_payload}</pre></details>`;
+            }
+          } else {
+            html += `<p style="color: #888; font-style: italic;">No cached status available for this unit.</p>`;
+          }
+
+          html += `</div>`;
+        }
+
+        // Fetch and display device logs
+        try {
+          const logsRes = await fetch(`/api/nl43/${unitId}/logs?limit=50`);
+          if (logsRes.ok) {
+            const logsData = await logsRes.json();
+            if (logsData.logs && logsData.logs.length > 0) {
+              html += `<div style="margin-top: 16px; border-top: 1px solid #d0d7de; padding-top: 12px;">`;
+              html += `<h4 style="margin: 0 0 12px 0;">📋 Device Logs (${logsData.stats.total} total)</h4>`;
+
+              // Stats summary
+              if (logsData.stats.by_level) {
+                html += `<div style="margin-bottom: 8px; font-size: 0.85em; color: #666;">`;
+                const levels = logsData.stats.by_level;
+                const parts = [];
+                if (levels.ERROR) parts.push(`<span style="color: #d00;">${levels.ERROR} errors</span>`);
+                if (levels.WARNING) parts.push(`<span style="color: #fa0;">${levels.WARNING} warnings</span>`);
+                if (levels.INFO) parts.push(`${levels.INFO} info`);
+                html += parts.join(' · ');
+                html += `</div>`;
+              }
+
+              // Log entries (collapsible)
+              html += `<details open><summary style="cursor: pointer; font-size: 0.9em; margin-bottom: 8px;">Recent entries (${logsData.logs.length})</summary>`;
+              html += `<div style="max-height: 300px; overflow-y: auto; background: #f6f8fa; border: 1px solid #d0d7de; border-radius: 4px; padding: 8px; font-size: 0.8em; font-family: monospace;">`;
+
+              logsData.logs.forEach(entry => {
+                const levelColor = {
+                  'ERROR': '#d00',
+                  'WARNING': '#b86e00',
+                  'INFO': '#0969da',
+                  'DEBUG': '#888'
+                }[entry.level] || '#666';
+
+                const time = new Date(entry.timestamp).toLocaleString();
+                html += `<div style="margin-bottom: 4px; border-bottom: 1px solid #eee; padding-bottom: 4px;">`;
+                html += `<span style="color: #888;">${time}</span> `;
+                html += `<span style="color: ${levelColor}; font-weight: 600;">[${entry.level}]</span> `;
+                html += `<span style="color: #666;">[${entry.category}]</span> `;
+                html += `${entry.message}`;
+                html += `</div>`;
+              });
+
+              html += `</div></details>`;
+              html += `</div>`;
+            }
+          }
+        } catch (logErr) {
+          console.log('Could not fetch device logs:', logErr);
+        }
+
         resultsEl.innerHTML = html;
         log(`Diagnostics complete: ${data.overall_status}`);