 }
 
 void mqttCallback(const char* topic_, const byte* payload_, unsigned int length) {
-  Serial.print("Message arrived [");
+  Serial.print(F("Message arrived ["));
   Serial.print(topic_);
-  Serial.print("] ");
+  Serial.print(F("] "));
   for (int i = 0; i < length; i++) {
     Serial.print((char)payload_[i]);
   }

  strncpy(payload, (char *)payload_, length);
  payload[length] = '\0';

  String sendTopic = globalTopic + "/send/";
  if (topic.startsWith(sendTopic)) {
    transmitt(topic.substring(sendTopic.length()), payload);
  }
  sendTopic = mainTopic + "/send/";
  if (topic.startsWith(sendTopic)) {
    transmitt(topic.substring(sendTopic.length()), payload);
  }
  if (topic == (mainTopic + "/set/raw")) {
    Serial.println("Change raw mode.");
    if (payload[0] == '1') {
      rawMode = true;
    }

  beatLED.on();
  // We start by connecting to a WiFi network
  Serial.println();
  Serial.print(F("Connecting to "));
  Serial.println(ssid);

  WiFi.begin(ssid, password);
