====== Smart ventilator example ======
This example shows how to make a temperature sensor controlled ventilator. You will need 2 controller modules. One
with DHT shield attached and the other with relay shield.

{{:en:iot:examples:20200610_212520.jpg?300|IoT controllers with DHT and relay shields}}

Once the code has been uploaded, the DHT controller will publish the temperature and humidity values to "temp" and "hum" every 2 seconds. The relay module subscribes to topics "temp" and "conf". The relay controller will switch the relay if the temperature rises above the set limit (default:28 degrees). To change the set limit, send a new value to the "conf" topic. (For example: "25.5")


The following is the code for the controller with relay module.
Required libraries:
<code>lib_deps = ITTIoT</code>
<code c>
// Includes global variables and librarys that the relay uses
#include <Arduino.h>
#include <ittiot.h>

#define WIFI_NAME "name"
#define WIFI_PASSWORD "password"

// Change it according to the real name of the red IoT module where
// temperature & humidity shield is connected
#define DHT_TOPIC "ESP30"

#define RELAY_PIN 5 // The relay has been connected to pin 5
float t; //for holding the received temperature float value
float tempLimit = 28; //the temperature limit on what the relay will switch

// Message received
void iot_received(String topic, String msg)
{
  t=msg.toFloat(); // Converts received temperature value into a real number

  // Check if topic contains configuration data (change the temperature limit value)
  if(topic == (DHT_TOPIC"/conf"))
  {
    //re-configures the temperature limit
    tempLimit=t;
  }

  // Check if topic contains temperature data
  if(topic == (DHT_TOPIC"/temp"))
  {
    // Relay switching according to the temperature limit value
    if(t >= tempLimit)
    {
      digitalWrite(RELAY_PIN, HIGH);
    }
    else
    {
      digitalWrite(RELAY_PIN, LOW);
    }
  }
}

// Function started after the connection to the server is established.
void iot_connected()
{
  // Send message to serial port to show that connection is established
  Serial.println("MQTT connected callback");
  // Subscribe to get temperature and temperature configuration messages
  iot.subscribe(DHT_TOPIC"/temp");
  iot.subscribe(DHT_TOPIC"/conf");
  // Send message to MQTT server to show that connection is established
  iot.log("Ventilator example!");
}

void setup()
{
  // Initialize serial port and send message
  Serial.begin(115200); // setting up serial connection parameter
  Serial.println("Booting");

  //iot.setConfig("wname", WIFI_NAME);
  //iot.setConfig("wpass", WIFI_PASSWORD);
  iot.printConfig(); // print IoT json config to serial
  iot.setup(); // Initialize IoT library

  pinMode(RELAY_PIN, OUTPUT); // The relay pin is defined as output type
}

void loop()
{
  iot.handle(); // IoT behind the plan work, it should be periodically called
  delay(20); // Wait 0.2 second
}

</code>

The following is the program code for the controller with DHT module.
Required libraries:
<code>lib_deps = ITTIoT, DHT sensor library, Adafruit Unified Sensor</code>
<fc #ff0000>After programming, if NAN appears instead of readings, the USB cable should be disconnected and reconnected!</fc>
<code c>
// Includes global variables and librarys that the DHT uses
#include <Arduino.h>
#include <ittiot.h>
#include <Ticker.h>
#include <DHT.h>

#define WIFI_NAME "name"
#define WIFI_PASSWORD "password"

#define DHTPIN D3     // Pin where DHT shield is connected. Change this to D4 if the shield has no legs removed.
#define DHTTYPE DHT22   // DHT 22  (AM2302)

// Create an object for DHT sensor
DHT dht(DHTPIN, DHTTYPE);

// Create an object for Ticker library
Ticker timeTicker;

bool sendDataFlag;

// Ticker library callback, which will occur 0.5 second interval.
void sendData()
{
  sendDataFlag=true;
}

// Function started after the connection to the server is established.
void iot_connected()
{
  // Send message to serial port to show that connection is established
  Serial.println("MQTT connected callback");
  // Send message to MQTT server to show that connection is established
  iot.log("IoT DHT example!");
}

void setup()
{
  // Initialize serial port and send message
  Serial.begin(115200); // setting up serial connection parameter
  Serial.println("Booting");

  //iot.setConfig("wname", WIFI_NAME);
  //iot.setConfig("wpass", WIFI_PASSWORD);
  iot.printConfig(); // print IoT json config to serial
  iot.setup(); // Initialize IoT library

  // Initialize DHT library
  dht.begin();

  // Initialize Ticker interval and callback
  timeTicker.attach(1, sendData);
}

void loop()
{
  iot.handle(); // IoT behind the plan work, it should be periodically called

  if(sendDataFlag)
  {
    sendDataFlag = false;
    // Read humidity and temperature
    float h = dht.readHumidity();
    float t = dht.readTemperature();

    // Create a buffer to store strings to being sent later
    char buf[10];

    // Convert temperature value messages to strings and send to the MQTT server
    String(t).toCharArray(buf,10);
    iot.publishMsg("temp",buf);

    // Convert humidity value messages to strings and send to the MQTT server
    String(h).toCharArray(buf,10);
    iot.publishMsg("hum",buf);
  }
}

</code>