First working version

src/main.cpp

@@ -57,7 +57,9 @@ void loop() {
 }
 
 void sensor_co2() {
+  serial2.listen();
   serial2.write(com,9);
   serial2.readBytes(return1,9);
   CO2 = return1[2]*256+return1[3];
+  serial1.listen();
 }