fix(watchdog): add ESP32 hardware reset via DTR/RTS

Since a standard USB bus reset often isn't enough to revive a hung ESP32, this adds a serial DTR/RTS toggle sequence (used by esptool) to physically reset the chip before trying a USB bus reset.

scripts/watchdog/watchdog.py

@@ -63,8 +63,8 @@ def log(message: str, level: str = 'INFO'):
 # USB Device Reset Constant
 USBDEVFS_RESET = 21780 # 0x5514
 
-def auto_detect_usb_device() -> str:
-    """Attempt to auto-detect the physical USB device path (e.g., /dev/bus/usb/001/002) for LoRa."""
+def auto_detect_serial_port() -> str:
+    """Detect the serial port (e.g., /dev/ttyACM0) from environment or by-id."""
     env_file = os.path.join(MCWEBUI_DIR, '.env')
     serial_port = 'auto'
     
@@ -85,7 +85,7 @@ def auto_detect_usb_device() -> str:
             if len(devices) == 1:
                 serial_port = str(devices[0])
             elif len(devices) > 1:
-                log("Multiple serial devices found, cannot auto-detect USB device for reset", "WARN")
+                log("Multiple serial devices found, cannot auto-detect single port", "WARN")
                 return None
             else:
                 log("No serial devices found in /dev/serial/by-id", "WARN")
@@ -97,12 +97,22 @@ def auto_detect_usb_device() -> str:
     if not serial_port or not os.path.exists(serial_port):
         log(f"Serial port {serial_port} not found", "WARN")
         return None
+        
+    try:
+        real_tty = os.path.realpath(serial_port)
+        return real_tty
+    except Exception as e:
+        log(f"Error resolving serial port {serial_port}: {e}", "ERROR")
+        return None
+
+def auto_detect_usb_device() -> str:
+    """Attempt to auto-detect the physical USB device path (e.g., /dev/bus/usb/001/002) for LoRa."""
+    real_tty = auto_detect_serial_port()
+    if not real_tty:
+        return None
 
     try:
-        # Resolve symlink to get actual tty device (e.g., /dev/ttyACM0)
-        real_tty = os.path.realpath(serial_port)
         tty_name = os.path.basename(real_tty)
-
         # Find USB bus and dev number via sysfs
         sysfs_path = f"/sys/class/tty/{tty_name}/device"
         if not os.path.exists(sysfs_path):
@@ -126,6 +136,42 @@ def auto_detect_usb_device() -> str:
         log(f"Error during USB device auto-detection: {e}", "ERROR")
         return None
 
+def reset_esp32_device():
+    """Perform a hardware reset on ESP32/LoRa device using DTR/RTS lines via ioctl."""
+    serial_port = auto_detect_serial_port()
+    if not serial_port:
+        log("Cannot perform ESP32 reset: serial port could not be determined", "WARN")
+        return False
+        
+    log(f"Performing ESP32 hard reset via DTR/RTS on {serial_port}", "WARN")
+    try:
+        import struct
+        import termios
+        
+        fd = os.open(serial_port, os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK)
+        
+        TIOCM_DTR = 0x002
+        TIOCM_RTS = 0x004
+        TIOCMBIS = getattr(termios, 'TIOCMBIS', 0x5416)
+        TIOCMBIC = getattr(termios, 'TIOCMBIC', 0x5417)
+        
+        # Reset sequence used by esptool
+        # DTR=False (Clear), RTS=True (Set) -> EN=Low
+        fcntl.ioctl(fd, TIOCMBIC, struct.pack('i', TIOCM_DTR))
+        fcntl.ioctl(fd, TIOCMBIS, struct.pack('i', TIOCM_RTS))
+        time.sleep(0.1)
+        
+        # DTR=False (Clear), RTS=False (Clear) -> EN=High
+        fcntl.ioctl(fd, TIOCMBIC, struct.pack('i', TIOCM_DTR | TIOCM_RTS))
+        time.sleep(0.05)
+        
+        os.close(fd)
+        log("ESP32 DTR/RTS reset sent successfully", "INFO")
+        return True
+    except Exception as e:
+        log(f"ESP32 DTR/RTS reset failed: {e}", "ERROR")
+        return False
+
 def reset_usb_device():
     """Perform a hardware USB bus reset on the LoRa device."""
     device_path = os.environ.get('USB_DEVICE_PATH')
@@ -326,6 +372,7 @@ def handle_unhealthy_container(container_name: str, status: dict):
             log(f"{container_name} has been restarted {recent_restarts} times in the last 8 minutes. Attempting hardware USB reset.", "WARN")
             # Stop the container first so it releases the serial port
             run_compose_command(['stop', container_name])
+            reset_esp32_device()
             if reset_usb_device():
                 time.sleep(5)  # Give OS time to re-enumerate the device
             restart_success = start_container(container_name)
@@ -402,6 +449,7 @@ def handle_unresponsive_device(container_name: str, status: dict):
             log(f"{container_name} has been restarted {recent_restarts} times in the last 8 minutes. Attempting hardware USB reset.", "WARN")
             # Stop the container first so it releases the serial port
             run_compose_command(['stop', container_name])
+            reset_esp32_device()
             if reset_usb_device():
                 time.sleep(5)  # Give OS time to re-enumerate the device
             restart_success = start_container(container_name)