2- Connect ESP8266 over MQTT

In this guide, we are going to publish data to the AskSensors IoT platform using an ESP8266 board and MQTT protocol.

Connect ESP8266 To AskSensors Over MQTT

a) Prerequisites :

b) Required Hardwares :

  • Computer running Arduino software (version 1.8.7 or higher).
  • ESP8266 board.
  • USB micro cable to connect the ESP8266 board to the computer.

c) Install ESP8266 in Arduino IDE :

  • Install the latest version of Arduino IDE software (1.8.7 or higher) from the official Arduino download page
  • Open the preferences window from the Arduino IDE : File> Preferences.
  • Go to the “Additional Board Manager URLs” field, Enter the following URL:
    http://arduino.esp8266.com/stable/package_esp8266com_index.json
  • Open boards manager (Tools > Board > Boards Manager), search for ESP8266 and click the install button for the “ESP8266 by Espressif Systems”. It takes some few seconds.

d) Software :

The provided code includes the libraries for both connecting to a WiFi network and to publish data to AskSensors using MQTT.
You need to fill the following:

    • Your WIFI SSID and password.
    • Your Asksensors username and Api Key In to set the MQTT Topic:publish/username/apiKeyIn

const char* ssid = "....."; // Wifi SSID
const char* password = ".....";// Wifi Password
const char* username = "................."; // my AskSensors username
const char* pubTopic = "publish/..../....."; // publish/username/apiKeyIn
const char* mqtt_server = "mqtt.asksensors.com";

e) Run the code

Now it’s time to connect your board.

  • Connect your ESP8266 board to the computer via serial/USB and upload the code using the Arduino IDE.
  • Return back to your sensor page on AskSensors, Click on’Show Graph’ and select the chart type (such as Line, Bar, Binary..) to visualize your sensor data stream in graph.
  • Open a serial terminal. You can cross-check the AskSensors graph readings with the values being printed on your Arduino Terminal.

f) Source Code :

A basic source code is shown below. Please refer to the AskSensors Github page to get the latest version and updates.


/*
* MQTT and AskSensors IoT Platform
* Description: ESP8266 sends data to AskSensors using MQTT
* Author: https://asksensors.com, 2020
* github: https://github.com/asksensors/AskSensors-ESP8266-MQTT
*/

#include <ESP8266WiFi.h>
#include <PubSubClient.h>

// TODO: AskSensors MQTT user config
const char* ssid = ".................."; // Wifi SSID
const char* password = ".................."; // Wifi Password
const char* username = "................."; // my AskSensors username
const char* pubTopic = "publish/..../....."; // publish/username/apiKeyIn
const unsigned int writeInterval = 25000; // write interval (in ms)
// MQTT host config
const char* mqtt_server = "mqtt.asksensors.com";
unsigned int mqtt_port = 1883;

WiFiClient askClient;
PubSubClient client(askClient);

void setup() {
Serial.begin(115200);
Serial.println("*****************************************************");
Serial.println("********** Program Start : ESP8266 publishes data to AskSensors over MQTT");
Serial.print("********** connecting to WIFI : ");
Serial.println(ssid);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("");
Serial.println("->WiFi connected");
Serial.println("->IP address: ");
Serial.println(WiFi.localIP());
client.setServer(mqtt_server, mqtt_port);
client.setCallback(callback);
}

void loop() {
if (!client.connected())
reconnect();
client.loop();
Serial.println("********** Publish MQTT data to ASKSENSORS");
char mqtt_payload[30] = "";
snprintf (mqtt_payload, 100, "m1=%ld&m2=%ld", random(10,100), random(10,100));
Serial.print("Publish message: ");
Serial.println(mqtt_payload);
client.publish(pubTopic, mqtt_payload);
Serial.println("> MQTT data published");
Serial.println("********** End ");
Serial.println("*****************************************************");
delay(writeInterval);// delay
}

void callback(char* topic, byte* payload, unsigned int length) {
Serial.print("Message arrived [");
Serial.print(topic);
Serial.print("] ");
for (int i = 0; i < length; i++) {
Serial.print((char)payload[i]);
}
Serial.println();
}

void reconnect() {
// Loop until we're reconnected
while (!client.connected()) {
Serial.print("********** Attempting MQTT connection...");
// Attempt to connect
if (client.connect("ESP8266Client",username, "")) {
Serial.println("-> MQTT client connected");
} else {
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println("-> try again in 5 seconds");
// Wait 5 seconds before retrying
delay(5000);
}
}
}

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