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Using the MAC address of an ESP8266’s WiFi adapter as the MQTT unique ID |
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######################################################################## |
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|
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:date: 2021-01-31T05:35:00Z |
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:category: blog |
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:tags: homeassistant,arduino |
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:url: blog/using-esp8266-macaddress-as-mqtt-unique-id/ |
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:save_as: blog/using-esp8266-macaddress-as-mqtt-unique-id/index.html |
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:status: published |
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:author: Gergely Polonkai |
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|
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|
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.. note:: |
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|
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This is a long story. If you are interested only in the solution, `click here <solution_>`__ |
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|
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The story |
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========= |
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|
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I recently dug my nose in the Arduino world, my goal being to build my own weather station. After |
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experimenting with Arduinos and other boards of different sizes, i finally settled using ESP8266 |
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based NodeMCU boards. They are cheap, have a well developed and maintained library for the |
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Arduino IDE, and can be accessed via WiFi so no cabling is needed throughout my house. |
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|
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The first version was based on Prometheus, running on a Raspberry Pi. Prometheus periodically |
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queried the station for the weather data, put it on a graph, and all was set… |
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|
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Except keeping a web server constantly up is really power consuming so it can’t be operated from a |
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battery; i had to install the station near a mains socket, which is in a place in wind shade, |
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providing less accurate temperature readings. It also takes away a precious wall socket, of which |
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i have only two outside. |
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|
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I got a little stuck in an X-Y problem, and started looking for another solution, based on a |
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Prometheus Push Gateway. While browsing documentation and generally hanging around the Interwebz, |
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i stumbled upon the Home Assistant project (which is on my ToDo list for a looong time). Without |
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hesitating, i quickly backed up the SD card of my Raspberry Pi and installed Hassio on it. I |
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never looked back since. |
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|
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With Home Assistant installed and configured, i installed and configured the Mosquitto add-on and |
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started tinkering with my ESP boards. |
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Logging the “weather” of my office (and adding a doorbell to the mix) |
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===================================================================== |
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|
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Since i didn’t want to dismantle the Prometheus based station yet (even though there was no-one to |
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query it except me calling ``http get http://192.168.0.12/metrics`` manually), i decided to |
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measure the temperature and humidity of my home office environment. |
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|
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The circuit is *really* simple: |
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- Take an ESP8266 board and a DHT22 sensor (you can go with a DHT11, it doesn’t really matter) |
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- Connect the GND, VCC, and OUT pins of the DHT sensor to the GND, 3V3, and D5 (any other pin can |
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work, though) |
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- Install the code below, and behold! |
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OK, i had a bit of precaution, and installed Mosquitto on my local machine, so i could test it |
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before sending data directly to Hassio. |
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|
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Meanwhile, i was expecting some package deliveries. I trusted the dogs that they will bark |
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whenever someone stops at our gate, which i can clearly hear in my office. Well, it turned out |
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they don’t do that if it’s raining, and since my smartphone rebooted for some unknown reason, the |
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delivery guy could not reach me and left; he will try to deliver the package again on Monday. All |
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this happened because i don’t have a doorbell. |
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So while at it, i quicly installed a push button on our gate, led the wire to my office (a good 5 |
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meters or so), and did some more soldering: |
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- Connect the GND pin of the ESP board to D4 through a 10kΩ resistor |
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- Connect one pin of the push button to the 3V3 pin of the ESP board |
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- Connect the other pin of the push button to the D4 pin of the ESP board |
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|
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This way D4 is pulled down (ie. remains low) all the time, and is pulled up (becomes high) when |
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someone pushes the button. |
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All is good, now to the coding part! |
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The code |
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======== |
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The code below is already tailored to be used with Home Assistant. While testing, ``BROKER_ADDR`` |
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pointed to my PC, and ``BROKER_USERNAME`` and ``BROKER_PASSWORD`` were not defined. |
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To compile it, you will need the Arduino IDE (or any toolchain that can compile Arduino code), the |
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ESP8266 board files for Arduino IDE, the Adafruit DHT library, and the `home-assistant-integration |
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<https://github.com/dawidchyrzynski/arduino-home-assistant>`_ library. |
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.. code-block:: c++ |
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#include <Adafruit_Sensor.h> |
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#include <ESP8266WiFi.h> |
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#include <ArduinoHA.h> |
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#include <DHT.h> |
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#define LED_PIN BUILTIN_LED |
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#define BROKER_ADDR IPAddress(192, 168, 0, 16) |
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#define BROKER_USERNAME "homeassistant" |
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#define BROKER_PASSWORD "verySecureHomeAssistantMQTTPassword" |
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#define BROKER_NAME "office-weather-station" |
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#define WIFI_SSID "MyHomeWiFi" |
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#define WIFI_PASSWORD "MyHomeWiFiPassword" |
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#define DHT_PIN D5 |
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#define DHT_TYPE DHT22 |
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#define DOORBELL_PIN D4 |
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#define UPDATE_INTERVAL 5000 |
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#define UNIQUE_ID "84cca8aa2673" |
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#define BUZZER_PIN D7 |
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WiFiClient client; |
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HADevice device(UNIQUE_ID); |
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HAMqtt mqtt(client, device); |
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HASwitch led("led", false, mqtt); |
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HABinarySensor doorbell("doorbell", false, mqtt); |
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HASensor<double> temperature("temperature", 0, mqtt); |
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HASensor<double> humidity("humidity", 0, mqtt); |
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unsigned long last_update = 0; |
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DHT dht(DHT_PIN, DHT_TYPE); |
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bool doorbell_pushed = false; |
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unsigned long doorbell_push_time = 0; |
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bool ringing = false; |
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void onSwitchStateChanged(bool state, HASwitch* s) |
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{ |
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digitalWrite(LED_PIN, (state ? LOW : HIGH)); |
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} |
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void setup() { |
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sensor_t sensor; |
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Serial.begin(9600); |
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Serial.println("Starting..."); |
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dht.begin(); |
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pinMode(LED_PIN, OUTPUT); |
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digitalWrite(LED_PIN, HIGH); |
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pinMode(DOORBELL_PIN, INPUT); |
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pinMode(BUZZER_PIN, OUTPUT); |
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// connect to wifi |
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WiFi.begin(WIFI_SSID, WIFI_PASSWORD); |
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while (WiFi.status() != WL_CONNECTED) { |
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Serial.print("."); |
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delay(500); // waiting for the connection |
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} |
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Serial.println(); |
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Serial.print("Connected to the network, IP address: "); |
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Serial.println(WiFi.localIP()); |
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// set device's details (optional) |
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device.setName(BROKER_NAME); |
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device.setSoftwareVersion("0.3.0"); |
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// handle switch state |
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led.onStateChanged(onSwitchStateChanged); |
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temperature.setUnitOfMeasurement("°C"); |
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humidity.setUnitOfMeasurement("%"); |
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mqtt.begin(BROKER_ADDR |
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#if defined(BROKER_USERNAME) && defined(BROKER_PASSWORD) |
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, BROKER_USERNAME, BROKER_PASSWORD |
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#endif |
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); |
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} |
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void loop() { |
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sensors_event_t event; |
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unsigned long now = millis(); |
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float temp_value; |
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float humid_value; |
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int doorbell_state = digitalRead(DOORBELL_PIN); |
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mqtt.loop(); |
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if ((doorbell_state == HIGH) && !doorbell_pushed) { |
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doorbell_pushed = true; |
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doorbell_push_time = now; |
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} else if ((doorbell_state == LOW) && doorbell_pushed) { |
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doorbell_pushed = false; |
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doorbell.setState(false); |
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ringing = false; |
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Serial.println("Doorbell released"); |
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analogWrite(BUZZER_PIN, 0); |
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delay(100); |
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} |
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if (doorbell_pushed && !ringing && (now - doorbell_push_time > 100)) { |
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ringing = true; |
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Serial.println("Doorbell pushed"); |
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doorbell.setState(true); |
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analogWrite(BUZZER_PIN, 255); |
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} |
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if ((now - last_update) >= UPDATE_INTERVAL) { |
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last_update = now; |
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temp_value = dht.readTemperature(); |
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temperature.setValue(temp_value); |
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Serial.print("Read temperature "); |
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Serial.println(temp_value); |
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humid_value = dht.readHumidity(); |
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humidity.setValue(humid_value); |
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Serial.print("Read humidity "); |
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Serial.println(humid_value); |
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} |
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} |
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|
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Nice, isn’t it? Well, can you see that ``UNIQUE_ID`` thing? That’s the ugly part, and that’s what |
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this article is about. |
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Into the depths of the ``home-assistant-integration`` |
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===================================================== |
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The NodeMCU example of the library goes like this (only the relevant parts are here): |
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.. code-block:: c++ |
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byte mac[6]; |
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WiFiClient client; |
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HADevice device(mac, sizeof(mac)); |
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HAMqtt mqtt(client, device); |
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HASwitch led("led", false, mqtt); // you can use custom name in place of "led" |
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void setup() { |
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WiFi.macAddress(mac); |
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WiFi.begin(WIFI_SSID, WIFI_PASSWORD); |
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mqtt.begin(BROKER_ADDRESS); |
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} |
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Now guess what the unique ID of the device will be. I’ll wait… |
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Was your answer “the MAC address of the ESP board’s WiFi chip”? Yeah, mine too. Except it will |
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be ``000000000000``. If you want to install one station in your house, that’s not a big deal. |
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But i want one outside, one in my office, in the kitchen, the bedroom, bathroom, and so one. |
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Having the same unique ID makes it not-so-unique in this case. So I dag deeper in the code of ``HADevice``. |
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It has the following constructors: |
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.. code-block:: c++ |
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HADevice::HADevice(const char *uniqueId) : |
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_uniqueId(uniqueId); |
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HADEVICE_INIT |
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{} |
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uint16_t HADevice::HADevice(const byte *uniqueId, const uint16_t &length) : |
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_uniqueId(HAUtils::byteArrayToStr(uniqueId, length)), |
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HADEVICE_INIT |
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{} |
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Meanwhile, the ``WiFi.macAddress(mac)`` line calls a function that *gets* the MAC address of the |
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WiFi chip, and stores the bytes in the ``mac`` array. |
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So what happens? How does the unique ID become a string of zeroes? |
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The example code calls the second constructor, effectively converting the ``mac`` array (full of |
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zeroes) to a character string full of zeroes. |
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The solution |
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============ |
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.. _solution: |
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As you can’t get the MAC address of the WiFi card outside of a function like ``setup()``, we can’t |
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rely on the second constructor form. However, the first form is more interesting if you look at |
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the code behind it: if you provide a string as the unique ID, it will be used without any |
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mangling. So let’s update our code a bit: |
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.. code-block:: c++ |
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#include <ESP8266WiFi.h> |
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#include <ArduinoHA.h> |
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#define LED_PIN D0 |
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#define BROKER_ADDR IPAddress(192, 168, 0, 17) |
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#define WIFI_SSID "MyNetwork" |
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#define WIFI_PASSWORD "MyPassword" |
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char macaddress[13]; |
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WiFiClient client; |
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HADevice device(macaddress); |
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HAMqtt mqtt(client, device); |
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HASwitch led("led", false, mqtt); // you can use custom name in place of "led" |
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void onSwitchStateChanged(bool state, HASwitch* s) |
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{ |
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digitalWrite(LED_PIN, (state ? HIGH : LOW)); |
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} |
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void setup() { |
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byte mac[6]; |
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Serial.begin(9600); |
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Serial.println("Starting..."); |
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WiFi.macAddress(mac); |
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pinMode(LED_PIN, OUTPUT); |
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digitalWrite(LED_PIN, LOW); |
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// connect to wifi |
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WiFi.begin(WIFI_SSID, WIFI_PASSWORD); |
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while (WiFi.status() != WL_CONNECTED) { |
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Serial.print("."); |
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delay(500); // waiting for the connection |
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} |
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Serial.println(); |
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Serial.println("Connected to the network"); |
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snprintf(macaddress, 13, |
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"%02x%02x%02x%02x%02x%02x", |
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mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]); |
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// set device's details (optional) |
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device.setName("NodeMCU"); |
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device.setSoftwareVersion("1.0.0"); |
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// handle switch state |
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led.onStateChanged(onSwitchStateChanged); |
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mqtt.begin(BROKER_ADDR); |
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} |
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void loop() { |
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mqtt.loop(); |
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} |
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|
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And now you have a unique(ish) ID (well, unless you start tinkering with MAC addresses on you network, but then you are on your own). |
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Loading…
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