Error flags: NPM deconnecte (0xFF) → ERR_NPM bit 3 dans byte 66

- npm_status 0xFF = pas de reponse du capteur → flag ERR_NPM (byte 66 bit 3)
  et byte 67 reste a 0x00 (pas de status valide a transmettre)
- npm_status valide → byte 67 tel quel, pas de flag dans byte 66

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

loop/SARA_send_data_v2.py

@@ -847,7 +847,15 @@ try:
     payload_csv[19] = npm_hum
 
     # npm_status: last value only (no average), use rowid (not timestamp)
-    npm_status_value = rows[0][7] if rows and rows[0][7] is not None else 0
+    npm_status_value = rows[0][7] if rows and rows[0][7] is not None else 0xFF
+
+    npm_disconnected = False
+    if npm_status_value == 0xFF:
+        # 0xFF = NPM disconnected/no response → will set ERR_NPM in error_flags
+        npm_disconnected = True
+        print("NPM status: 0xFF (disconnected)")
+    else:
+        # Valid status from NPM → send as byte 67
         payload.set_npm_status(npm_status_value)
         print(f"NPM status: 0x{npm_status_value:02X}")
 
@@ -1139,6 +1147,8 @@ try:
         error_flags |= ERR_RTC_DISCONNECTED
     if rtc_status == "reset":
         error_flags |= ERR_RTC_RESET
+    if npm_disconnected:
+        error_flags |= ERR_NPM
     payload.set_error_flags(error_flags)
 
     # ---- Firmware version (bytes 69-71) ----