 
 const char* ssid = "ssid";
 const char* password = "password";
+#define LED_BUILTIN 2
 
 const char* mqtt_server = "mqtt_server";
 

  char c_payload[length];
  memcpy(c_payload, payload, length);
  c_payload[length] = '\0';

  Serial.printf("<- %s: %s\n", topic, c_payload);
}

void loop() {

void setup() {
  Serial.begin(115200);

  pinMode(LED_BUILTIN, OUTPUT);
  // HIGH means OFF on ESP-12E.
  digitalWrite(LED_BUILTIN, HIGH);
  
  sprintf(stationID, "%d", ESP.getChipId());

  setup_wifi();
