Published May 9, 2018 © MIT

Control an ESP8266 via Wia's MQTT API

Go through setting up an ESP8266 board, and subscribing to a Wia Command via MQTT. This will allow you to control your Device with Wia!

BeginnerFull instructions provided1 hour3,093

Things used in this project

Hardware components

Espressif ESP8266 ESP-01

Software apps and online services

Wia

Story

CONNECTING THE BOARD

Note: If your board has a micro USB port, you can probably skip this step.

Connect your board to laptop/desktop via a USB to TTL cable/adapter. Here's a pinout showing the different connections.

Connections between the ESP and USB TTL are the following:

ESP8266 <-> USB TTL

GND <-> GND

TX <-> RX

VCC <-> 3.3V(+)

CH_PD <-> 3.3V(+)

GPIO0 <-> GND (Only while flashing the board)

SETUP YOUR ENVIRONMENT

Install the Arduino IDE. You can download it for Mac OS X, Windows and Linux here

Start the Arduino application and open Preferences

Enter http://arduino.esp8266.com/stable/package_esp8266com_index.json into the Additional Board Manager URLs. If you need more than one, they can be separated with commas

Go toTools > Board > Boards ManagerSearch for esp8266. When found, click Install

Select your ESP8266 board type by going to Tools > Board, then choosing your type. For this example I am using NodeMCU 1.0 (ESP-12E Module).

You can get the name of your device's port using one of the following steps:

Linux and Mac OS X

Download and install the FTDI drivers from here. Select the appropriate version for your operating system and architecture

Open a terminal window and run the Command ls /dev/tty*

Look for a device with the name that begins with /dev/tty e.g. /dev/tty.usbmodemPy343431 on MAC or /dev/ttyUSB0/dev/ttyACM0 on Linux

Note: For Linux, you may need to run the two Commands below. Once you've completed that, reboot your computer. This will add permissions that will allow you to upload a sketch to the board.

`sudo usermod -a -G tty ${USER}``sudo usermod -a -G dialout  ${USER}`

Windows

Download and install the FTDI drivers from here. Select the appropriate version for your operating system and architecture

Open the Windows start menu and search for Device Manager

The COM port for the ESP8266 device will be listed as USB Serial Device or something similar

Keep note of the COM port (e.g. COM4)

INSTALL THE REQUIRED LIBRARIES

In the Arduino IDE, Go to Sketch > Include Libraries > Manage LibrariesInstall each of the following libraries by searching for their name in the search bar within the modal. A button will appear in the bottom right of the box that will allow you to install the library.

ESP8266WiFi

PubSubClient

ArduinoJson

ADD A DEVICE AND COMMAND IN WIA

If you haven't already, you'll need create a Device and add a Command to your Wia account. Tutorials can be found here to add a Device and here to add a Command.

CREATE THE SKETCH

In the Arduino IDE:

Click on File > New to create a new Sketch

Copy and paste the example code below labeled Wia Command. This code subscribes to a Wia Command

The callback contains a placeholder section to write code to do something useful when a Command has been triggered

Replace the following values of the following variables:

your-wifi-ssid - with your WiFi network name

your-wifi-password - with your WiFi network password

your-device-id with your Device id from the Wia Dashboard (the one that begins with dev_)

your-device_secret_key with your Device secret key from the Wia Dashboard (the one that begins with d_sk)

Go to Sketch > Upload in the Arduino IDE menu to send it to your ESP8266

Open your Serial Monitor to view the output from your ESP8266 by going to Tools > Serial Monitor

Go to the Wia dashboard in the Command section and click run on the Command associated with the code above.

Wia Command

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

const char* ssid = "Your Wifi ssid";   // Your Wifi ssid
const char* password =  "password";   // Your Wifi password

const char* mqttServer = "api.wia.io" // mqtt://api.wia.io
const int mqttPort = 1883;  // Default MQTT port

const String deviceId = "Device Id";   // starts with dev_, found in Wia Dashboard
const String deviceSecretKey = "Device Secret Key";  // Starts with d_sk_, found in Wia Dashboard

const String commandName = "check-temperature";  // Configured in Wia Dashboard

String topic = "devices/" + deviceId + "/commands/" + commandName + "/run";

// Instantiating a WiFiClient and  
passing it into the PubSubClient
WiFiClient espClient;
PubSubClient client(espClient);


// The function that handles the response from the Command
void callback(char* topic, byte* payload, unsigned int length) {

  Serial.print("Command initiated: ");
  Serial.println(topic);
   
  // Add functionality for command here i.e (Check the temperature)

}

void reconnect() {
  while (!client.connected()) {
    Serial.println("Connecting to MQTT...");

    if (client.connect("ESP8266Client", deviceSecretKey, " ")) {

      Serial.println("connected");

    } else {
      Serial.print("failed with state ");
      Serial.print(client.state());
      delay(2000);
    }
  }

  // Converts to String to char array to pass to PubSubClient
  char topicChar[100];
  topic.toCharArray(topicChar, topic.length() + 1);
  Serial.print("Subscribed to: ");
  Serial.println(topic);

  // Subscribe to the command topic
  client.subscribe(topicChar);
}

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

  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.println("Connecting to WiFi..");
  }
  Serial.println("Connected to the WiFi network");

  client.setServer(mqttServer, mqttPort);
  client.setCallback(callback);
}


void loop() {
  if (!client.connected()) {
    reconnect();
  }
  // Continiously loop to check if a command has been initiated
  client.loop();
}