I’m trying to use a sketch from this repository which uses MQTT to send a notification to Home-Assistant that acts a “presence sensor”. When the NodeMCU comes into range of the specified SSID, the controller connects to WiFi and sends a MQTT message to home-assistant which can then perform some home automation commands. This code does exactly that. The MQTT messages are sent and received.

What is not working is that I can’t update the sketch over the air (OTA) via the included ArduinoOTA library. After uploading this sketch to the NodeMCU, it connects to WiFi and I am getting a message from the console output that the device is ready for OTA updates. From everything that I’ve read I beleive there is supposed to be an option in the Arduino menus where I can specify that I want to update OTA instead of a com port. How can I enable this in the IDE? Also, is there a way to “connect” to the serial monitor so that I can also see the output OTA?

I’m attaching the sketch for your convenience:

// Modify these values for your environment
const char* wifiSSID = "wifissid";  // Your WiFi network name
const char* wifiPassword = "wifipassword";  // Your WiFi network password
const char* otaPassword = "myotapassword";  // OTA update password
const char* mqttServer = "";  // Your MQTT server IP address
const char* mqttUser = ""; // mqtt username, set to "" for no user
const char* mqttPassword = ""; // mqtt password, set to "" for no password
const String mqttNode = "CarPresence"; // Your unique hostname for this device
const String mqttDiscoveryPrefix = "homeassistant"; // Home Assistant MQTT Discovery, see https://home-assistant.io/docs/mqtt/discovery/

// Home Assistant MQTT Discovery, see https://home-assistant.io/docs/mqtt/discovery/
// We'll create one binary_sensor device to track MQTT connectivity
const String mqttDiscoBinaryStateTopic = mqttDiscoveryPrefix + "/binary_sensor/" + mqttNode + "/state";
const String mqttDiscoBinaryConfigTopic = mqttDiscoveryPrefix + "/binary_sensor/" + mqttNode + "/config";
// And a sensor for WiFi signal strength
const String mqttDiscoSignalStateTopic = mqttDiscoveryPrefix + "/sensor/" + mqttNode + "-signal/state";
const String mqttDiscoSignalConfigTopic = mqttDiscoveryPrefix + "/sensor/" + mqttNode + "-signal/config";
// And a sensor for device uptime
const String mqttDiscoUptimeStateTopic = mqttDiscoveryPrefix + "/sensor/" + mqttNode + "-uptime/state";
const String mqttDiscoUptimeConfigTopic = mqttDiscoveryPrefix + "/sensor/" + mqttNode + "-uptime/config";

// The strings below will spill over the PubSubClient_MAX_PACKET_SIZE 128
// You'll need to manually set MQTT_MAX_PACKET_SIZE in PubSubClient.h to 512
const String mqttDiscoBinaryConfigPayload = "{\"name\": \"" + mqttNode + "\", \"device_class\": \"connectivity\", \"state_topic\": \"" + mqttDiscoBinaryStateTopic + "\"}";
const String mqttDiscoSignalConfigPayload = "{\"name\": \"" + mqttNode + "-signal\", \"state_topic\": \"" + mqttDiscoSignalStateTopic + "\", \"unit_of_measurement\": \"dBm\", \"value_template\": \"{{ value }}\"}";
const String mqttDiscoUptimeConfigPayload = "{\"name\": \"" + mqttNode + "-uptime\", \"state_topic\": \"" + mqttDiscoUptimeStateTopic + "\", \"unit_of_measurement\": \"msec\", \"value_template\": \"{{ value }}\"}";

// Set the signal strength and uptime reporting interval in milliseconds
const unsigned long reportInterval = 5000;
unsigned long reportTimer = millis();

// Set LED "twinkle" time for maximum daylight visibility
const unsigned long twinkleInterval = 50;
unsigned long twinkleTimer = millis();

#include <ESP8266WiFi.h>
#include <ESP8266mDNS.h>
#include <WiFiUdp.h>
#include <ArduinoOTA.h>
#include <PubSubClient.h>

WiFiClient wifiClient;
PubSubClient mqttClient(wifiClient);

// System setup
void setup() {
  digitalWrite(LED_BUILTIN, HIGH);

  Serial.println("\nHardware initialized, starting program load");

  // Start up networking

  // Create server and assign callbacks for MQTT
  mqttClient.setServer(mqttServer, 1883);

  // Start up OTA
  if (otaPassword[0]) {

  Serial.println("Initialization complete\n");

// Main execution loop
void loop() {
  // check WiFi connection
  if (WiFi.status() != WL_CONNECTED) {

  // check MQTT connection
  if (!mqttClient.connected()) {

  // MQTT client loop
  if (mqttClient.connected()) {

  // LED twinkle
  if (mqttClient.connected() && ((millis() - twinkleTimer) >= twinkleInterval)) {
    digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
    twinkleTimer = millis();

  // Report signal strength and uptime
  if (mqttClient.connected() && ((millis() - reportTimer) >= reportInterval)) {
    String signalStrength = String(WiFi.RSSI());
    String uptimeTimer = String(millis());
    mqttClient.publish(mqttDiscoSignalStateTopic.c_str(), signalStrength.c_str());
    mqttClient.publish(mqttDiscoUptimeStateTopic.c_str(), uptimeTimer.c_str());
    reportTimer = millis();

  // OTA loop
  if (otaPassword[0]) {

// Functions

// Handle incoming commands from MQTT
void mqtt_callback(char* topic, byte* payload, unsigned int payloadLength) {

// Connect to WiFi
void setupWifi() {
  Serial.print("Connecting to WiFi network: " + String(wifiSSID));
  WiFi.begin(wifiSSID, wifiPassword);

  while (WiFi.status() != WL_CONNECTED) {
    // Wait 500msec seconds before retrying
  Serial.println("\nWiFi connected successfully and assigned IP: " + WiFi.localIP().toString());

// MQTT connection and subscriptions
void mqttConnect() {
  digitalWrite(LED_BUILTIN, HIGH);
  Serial.println("Attempting MQTT connection to broker: " + String(mqttServer));
  // Attempt to connect to broker, setting last will and testament
  if (mqttClient.connect(mqttNode.c_str(), mqttUser, mqttPassword, mqttDiscoBinaryStateTopic.c_str(), 1, 1, "OFF")) {
    // when connected, record signal strength and reset reporting timer
    String signalStrength = String(WiFi.RSSI());
    reportTimer = millis();
    String uptimeTimer = String(millis());
    // publish MQTT discovery topics and device state
    Serial.println("MQTT discovery connectivity config: [" + mqttDiscoBinaryConfigTopic + "] : [" + mqttDiscoBinaryConfigPayload + "]");
    Serial.println("MQTT discovery connectivity state: [" + mqttDiscoBinaryStateTopic + "] : [ON]");
    Serial.println("MQTT discovery signal config: [" + mqttDiscoSignalConfigTopic + "] : [" + mqttDiscoSignalConfigPayload + "]");
    Serial.println("MQTT discovery signal state: [" + mqttDiscoSignalStateTopic + "] : " + WiFi.RSSI());
    Serial.println("MQTT discovery uptime config: [" + mqttDiscoUptimeConfigTopic + "] : [" + mqttDiscoUptimeConfigPayload + "]");
    Serial.println("MQTT discovery uptime state: [" + mqttDiscoUptimeStateTopic + "] : " + uptimeTimer);
    mqttClient.publish(mqttDiscoUptimeConfigTopic.c_str(), mqttDiscoUptimeConfigPayload.c_str(), true);
    mqttClient.publish(mqttDiscoUptimeStateTopic.c_str(), uptimeTimer.c_str());
    mqttClient.publish(mqttDiscoBinaryConfigTopic.c_str(), mqttDiscoBinaryConfigPayload.c_str(), true);
    mqttClient.publish(mqttDiscoBinaryStateTopic.c_str(), "ON");
    mqttClient.publish(mqttDiscoSignalConfigTopic.c_str(), mqttDiscoSignalConfigPayload.c_str(), true);
    mqttClient.publish(mqttDiscoSignalStateTopic.c_str(), signalStrength.c_str());
    Serial.println("MQTT connected");
    digitalWrite(LED_BUILTIN, LOW);
  else {
    Serial.println("MQTT connection failed, rc=" + String(mqttClient.state()));

// (mostly) boilerplate OTA setup from library examples
void setupOTA() {
  // Start up OTA
  // ArduinoOTA.setPort(8266); // Port defaults to 8266

  ArduinoOTA.onStart([]() {
    Serial.println("ESP OTA:  update start");
  ArduinoOTA.onEnd([]() {
    Serial.println("ESP OTA:  update complete");
  ArduinoOTA.onProgress([](unsigned int progress, unsigned int total) {
    //Serial.printf("Progress: %u%%\r", (progress / (total / 100)));
  ArduinoOTA.onError([](ota_error_t error) {
    Serial.println("ESP OTA:  ERROR code " + String(error));
    if (error == OTA_AUTH_ERROR) Serial.println("ESP OTA:  ERROR - Auth Failed");
    else if (error == OTA_BEGIN_ERROR) Serial.println("ESP OTA:  ERROR - Begin Failed");
    else if (error == OTA_CONNECT_ERROR) Serial.println("ESP OTA:  ERROR - Connect Failed");
    else if (error == OTA_RECEIVE_ERROR) Serial.println("ESP OTA:  ERROR - Receive Failed");
    else if (error == OTA_END_ERROR) Serial.println("ESP OTA:  ERROR - End Failed");
  Serial.println("ESP OTA:  Over the Air firmware update ready");

2 Answers 2


Follow the instruction here https://arduino-esp8266.readthedocs.io/en/latest/ota_updates/readme.html#application-example

First load the OTA example specified. Do not waste your time implementing it in your code until you have the supplied example working.

If you are running Windows then it helps to have an application called Bonjour Browser. The OTA method makes use of mDNS. I use Bonjour Browser to confirm that the ESP is being seen. Then I go to ports in the IDE and there is an entry for the newly added OTA device.

Select the entry instead of the com ports. Then compile and upload.

If you get an error then do a power cycle on the ESP board. You should only need to do this once after the serial upload.

I use this method but sometimes the device does not appear below the com listed. I have had to close and restart the IDE to refresh the device listing. (I think this is a Windows issue) Because of this I prefer the webupdater method. https://arduino-esp8266.readthedocs.io/en/latest/ota_updates/readme.html#web-browser

  • good answer Rudy. In Sloeber (Arduino Eclipse plugin) I can enter the IP address and must not relay on mDNS
    – Juraj
    Nov 5, 2018 at 5:15
  • of the available OTA methods, this one is the simplest imho.
    – dandavis
    Nov 5, 2018 at 20:29

Done this form a Linux laptop's command line.

For uploading to Arduino boards, I have been using (via the usual USB port connection) the command line methods as detailed at: https://github.com/arduino/Arduino/blob/master/build/shared/manpage.adoc For the OTA method of uploading to the ESP, I just chanced to discover the following method.

As the argument to "--port", I just used the ip of the wifi connected ESP board.

Let us say I want to upload a sketch "myexample1.ino" to my ESP8266 board "ESP-01 (1MB)" having OTA firmware on it. Am using Arduino 1.8.8 and ESP8266 community version 2.4.2. As already stated, the ESP-01 has the example sketch "BasicOTA.ino" uploaded to it via the usual USB port. Now, the ESP-01 is not connected via USB. It is connected to my wifi router at an ip (say, The following command successfully uploaded the code:

~/Arduino/myexample1 $ arduino --upload myexample1.ino --port

Just felt like sharing a nice experience not found reported elsewhere on the internet.

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