GPRS Communication with PC Client over MQTT Protocol : IOT Part 27

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//Program to
 /*

  @Project: SIM800_communication_over_MQTT_protocol

  

  @Hardware used:

     SIM800 Module

     Arduino Mega 2560

     LED & 220E resistor

     External Power supply to provide 3.7V to SIM800 module

  

  @Connection:

       SIM800 VCC- External power supply 3.7V

       SIM800 GND- External power supply GND

       SIM800 TX- Arduino Serial1 RX

       SIM800 RX- Arduino Serial1 TX

       SIM800 GND- Arduino GND

       LED cathode- Arduino 2nd pin with 220E resistor in Series   

       LED anode-  Arduino GND 

       External power supply GND- Arduino GND

       

  @Brief Introduction: 

       In this application, We have used SIM800 as our first MQTT client and PC(MQTTlens) 
as our second MQTT client.

       We are using hiveMQ as our MQTT broker. We are using Arduino Mega to provide serial
 communication to SIM800 client. 

       PC client is controlling the LED of SIM800 client & SIm800 client is publishing 
the message "Welcome to GPRS NETWORK!" on topic "GPRS_pub"

*/



//Initialize the SIM to connect to the Network

#define SIM_APN        "Airtelgprs.com"           //APN Name, We are using Airtel network

#define SIM_USER       ""      //APN USER, We haven't set any username so leave it blank

#define SIM_PASSWORD    ""           //APN PASSWORD, We haven't set any password so leave it blank


//Include Libraries

#include 

#include                         //Include library to initialize SIM800 client

#include                    //Include library to initlize MQTT protocol

#include 


//Create the instance for SIM800

sim800Client s800;

char imeicode[16];           //Array initialization for IMEI code so as to find out the device is valid or not.


/*

 MQTT broker on which our device is going to be connected! 

 We are using hiveMQ public broker with unencrypted channel

 We can change the broker according to our requirement

*/

char server[] = "broker.mqttdashboard.com";  


/*

 @fn: void callback(char* topic, byte* payload, unsigned int length)

 @Param: topic, payload, payload length

          Topic: the subsription topic, SIM800 client has subscribed

          payload: the message we receive from MQTT broker on the subcribed topic

          length: the message length

  @return: None

 @brief: This callback function will be called whenever SIM800 client receives the
 message on topic GPRS_sub/LED_control

*/

void receive_message(char* topic, byte* payload, unsigned int length) 

{

  //handle message arrived

  char mypl[48];

  Serial.println(length);

  memcpy(mypl,payload,length);

  mypl[length]=char(0);

  Serial.print("receive: ");

  Serial.print(topic);

  Serial.print("->");

  Serial.println(mypl);

  

  /*

   When the client receives message 1, LED will be in ON state

   When the client receives message 0, LED will be in OFF state

  */

  if ((char)payload[0]== '1')

  digitalWrite(2, HIGH);

  else if ((char)payload[0]== '0')

   digitalWrite(2, LOW);

}


/*

  @Create the instace for pubsub client

  @Param: server- MQTT server which we have initialized above

          1883- The port on which MQTT broker is listening

          callback- The function for subscription which we have initialized above

          s800- SIM800 client which we have created above

*/

PubSubClient client(server, 1883, receive_message, s800);


/*

  @fn void pub()

  @Param: None

  @Brief: Created a function through which S800 client will publish the message with topic to the MQTT broker

          Whenever we want to change the publish topic and message, we can change from here.

  @return: None

*/

void publish_message()

{

  Serial.print("publish: ");

  Serial.print("message on topic GPRS_pub");

  Serial.print("-> ");

  Serial.println("Welcome to GPRS NETWORK!");

  

  /*

   @fn client.publish(Topic, message);

   @Param: Topic, message

            Topic- The topic on which our message is going to be published

            Message- Any message on the respective topic

   @brief: Call this function to publish the message on MQTT broker

  */

  client.publish("GPRS_pub","Welcome to GPRS NETWORK!");

}


void setup()

{

  

  pinMode(2, OUTPUT);      //Initialize LED as OUTPUT so that other client can control this LED

  Serial.begin(9600);        //Start the serial communication to debug the communication

  Serial.println("SIM800 MQTT TESTING");

  

  for (int i=0; i<10; i++)

  {

    delay(5000);

    Serial.println("Initialize SIM800!");


   #ifdef HARDWARESERIAL

      if (s800.init( 7, 6)) break; 

   #else

       if (s800.init(&Serial1 , 7, 6)) break;                 //Initialize the serial communication for SIM800 

   #endif

  }


  Serial.println("SETUP SIM800!");

  s800.setup();              //Initialize setup for SIM800 client

  s800.stop();              //stop any previous network connection of the SIM800 client 

  s800.TCPstop();           //Stop any previous TCP connection of SIM800 client

  s800.getIMEI(imeicode);      //Get the IMEI code of he SIM800 client                                

  Serial.print("IMEI: ");

  Serial.println(imeicode);


  //From this loop, Start the continuous TCP connection with APN, USERNAME and PASSWORD

  while (!s800.TCPstart(SIM_APN,SIM_USER,SIM_PASSWORD)) 

  { 

    Serial.println("TCPstart failed");

    s800.TCPstop();

    delay(1000);

  }

  Serial.println("TCPstart started");

  

  //From this loop,the client will be connected to the Network

  while (!client.connect(imeicode)) {

    Serial.println("connect failed");

    delay(1000);

  }


  Serial.println("connected");

    /*

   @fn client.subscribe(Topic);

   @Param: Topic

            Topic- The topic on which we receive the message

   @brief: Call this function to subsribe the topic from MQTT broker

  */

  client.subscribe("GPRS_sub/LED_control"); 


  //From this function, the message will be published in a repetitive period of 5 sec to the MQTT broker

  Alarm.timerRepeat(5, publish_message);           

}


void loop()

{

    client.loop();

    Alarm.delay(100); 


}


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