EMQX_BMP280_OLED.txt

//File Name:- EMQX_BMP280_OLED
//Hardware is same to that of BM280 Program
//This Program displays Temp.,Press., and Altitude on OLED
//This Program displays Temp.,Press., on EMQX client 
// The client values changes when Temp and Press changes by 0.01

#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BMP280.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
#define OLED_RESET LED_BUILTIN 
#define Sea_Level_Press_hPa (1013.25)

// WiFi
const char* ssid = "";  // Enter SSID of your Wi-Fi here
const char* password = "";  //Enter Password of your Wi-Fi here
// MQTT Broker
const char *mqtt_broker = "broker.emqx.io";
const char *topic="NodeMCU_BMP_Test";
const char *mqtt_username = "emqx";
const char *mqtt_password = "public";
const int   mqtt_port = 1883;
const char *temperature_topic="BMP_Temperature";
const char *pressure_topic="BMP_Pressure";

WiFiClient NodeMCUClient;
PubSubClient client(NodeMCUClient);

Adafruit_BMP280 bmp;
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire,OLED_RESET);

void setup() {
 Serial.begin(9600);
 delay(100);

if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
 Serial.println(F("SSD1306 allocation failed"));
 for(;;);
 }
 display.clearDisplay();
 display.setTextColor(WHITE);
 delay(2000);
 
bool status = bmp.begin(0x76); 
if (!status) {
Serial.println("Could not find a valid BMP280 sensor, check wiring!");
while(1);
}
delay(500);

Serial.println("");//Flushout Garbage
  // connecting to a WiFi network
  Serial.println("connecting to:");
  Serial.println(ssid);
  WiFi.begin(ssid,password);//connect to your Local WiFi Network
  while(WiFi.status()!=WL_CONNECTED){
    delay(1000);
    Serial.print(".");
    }
  Serial.println("");
  Serial.println("WiFi Connected!");
  Serial.print("Got IP:");
  Serial.println(WiFi.localIP());
  
  client.setServer(mqtt_broker, mqtt_port);
  client.setCallback(callback);  
}
 
  
//---------------
  void reconnect() {
  // Loop until we're reconnected
  //client.setServer(mqtt_broker, mqtt_port);  
  //client.setCallback(callback);
  while (!client.connected()) {
    Serial.print("Attempting EMQ X_MQTT connection...");
    // Attempt to connect
    // If you do not want to use a username and password, change next line to
    // if (client.connect("ESP8266Client")) {
    if (client.connect("NodeMCUClient", mqtt_username, mqtt_password)) {
      Serial.println("Public emqx MQTT broker connected");
    } else {
      Serial.print("failed, rc= ");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
  client.publish(topic,"hello emqx");
  client.subscribe(topic);
  }

bool checkBound(float newValue, float prevValue, float maxDiff) {
  return !isnan(newValue) &&
         (newValue < prevValue - maxDiff || newValue > prevValue + maxDiff);
}

long lastMsg = 0;
float temp = 0.0;
float pres = 0.0;
float diff = 0.01;


 void loop(){
    if (!client.connected()){
      reconnect();
    }
    client.loop();
      long now = millis();
  if (now - lastMsg > 1000) {
    lastMsg = now;
    float newTemp = bmp.readTemperature();
    float newPres = bmp.readPressure()/100.0F;
    if (checkBound(newTemp, temp, diff)) {
      temp = newTemp;
      Serial.print("New temperature:");
      Serial.println(String(temp).c_str());
      client.publish(temperature_topic, String(temp).c_str(), true);
 display.setTextSize(1);
 display.setCursor(0,0);
 display.print("Temperature: ");
 display.setTextSize(1);
 display.setCursor(0,10);
 display.print(String(temp).c_str());
 display.print(" ");
 display.setTextSize(1);
 display.cp437(true);
 display.write(167);
 display.setTextSize(1);
 display.print(" C");
 delay(1000);
}
    if (checkBound(newPres, pres, diff)) {
      pres = newPres;
      Serial.print("New pressure:");
      Serial.println(String(pres).c_str());
      client.publish(pressure_topic, String(pres).c_str(), true);
 display.setTextSize(1);
 display.setCursor(0, 20);
 display.print("Pressure: ");
 display.setTextSize(1);
 display.setCursor(0, 30);
 display.print(String(pres).c_str());
 display.print(" hPa"); 
 display.display();
 delay(1000); 
    }
  
//display altitude
 display.setTextSize(1);
 display.setCursor(0, 40);
 display.print("Altiitude: ");
 display.setTextSize(1);
 display.setCursor(0, 50);
 display.print(String(bmp.readAltitude(Sea_Level_Press_hPa)));
 display.print(" m"); 
 display.display();
 delay(1000);

 display.clearDisplay();
 //client.loop();
 }
   delay(1000);
  }
 
 void callback(char *topic1, byte *payload, unsigned int length) {
 Serial.print("Message arrived in topic: ");
 Serial.println(topic1);
 Serial.print("Message:");
 for (int i = 0; i < length; i++) {
     Serial.print((char) payload[i]);
 }
 Serial.println();
 Serial.println("-----------------------");
}