fix(mhz19): gestion d'erreurs JSON pour le capteur CO2

Le script get_data.py retourne maintenant toujours du JSON, meme en cas
d'erreur (port serie, absence de donnees). Cote web, les erreurs sont
affichees proprement dans la carte capteur.

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

MH-Z19/get_data.py

@@ -12,47 +12,42 @@ import time
 parameter = sys.argv[1:]
 port = '/dev/' + parameter[0]
 
-ser = serial.Serial(
-    port=port,
-    baudrate=9600,
-    parity=serial.PARITY_NONE,
-    stopbits=serial.STOPBITS_ONE,
-    bytesize=serial.EIGHTBITS,
-    timeout=1
-)
-
-READ_CO2_COMMAND = b'\xFF\x01\x86\x00\x00\x00\x00\x00\x79'
-
 
 def read_co2():
-    ser.write(READ_CO2_COMMAND)
-    time.sleep(2)
-    response = ser.read(9)
-    if len(response) < 9:
-        print("Error: No data or incomplete data received.")
-        return None
-    if response[0] == 0xFF:
-        co2_concentration = response[2] * 256 + response[3]
-        return co2_concentration
-    else:
-        print("Error reading data from sensor.")
-        return None
-
-
-def main():
     try:
-        co2 = read_co2()
-        if co2 is not None:
-            data = {"CO2": co2}
-            json_data = json.dumps(data)
-            print(json_data)
+        ser = serial.Serial(
+            port=port,
+            baudrate=9600,
+            parity=serial.PARITY_NONE,
+            stopbits=serial.STOPBITS_ONE,
+            bytesize=serial.EIGHTBITS,
+            timeout=1
+        )
+    except serial.SerialException as e:
+        print(json.dumps({"error": f"Serial port error: {e}"}))
+        return
+
+    READ_CO2_COMMAND = b'\xFF\x01\x86\x00\x00\x00\x00\x00\x79'
+
+    try:
+        ser.write(READ_CO2_COMMAND)
+        time.sleep(2)
+        response = ser.read(9)
+
+        if len(response) < 9:
+            print(json.dumps({"error": "No data or incomplete data received from sensor"}))
+            return
+
+        if response[0] == 0xFF:
+            co2_concentration = response[2] * 256 + response[3]
+            print(json.dumps({"CO2": co2_concentration}))
         else:
-            print("Failed to get CO2 data.")
-    except KeyboardInterrupt:
-        print("Program terminated.")
+            print(json.dumps({"error": "Invalid response from sensor"}))
+    except Exception as e:
+        print(json.dumps({"error": str(e)}))
     finally:
         ser.close()
 
 
 if __name__ == '__main__':
-    main()
+    read_co2()