D1 Mini Lite v1 temp/humidity sensor with OLED 0.96" screen and MQTT output

temp_humidity_oled_mqtt.ino

/*
 * This code is hacked together from 2 separate temp/humidity sensor projects for MQTT and OLED output
 * Pinout is below this line
 * OLED GND=GND VCC=VCC SCL=D1 SCA=D2
 * DHT22 -=GND OUT=D4 +=VCC
 * D1 Mini Lite GND=GND VCC=3v3
*/
#include <SPI.h>
#include <Wire.h>
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include "DHT.h"


#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     -1 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

#define DHTPIN 2
#define DHTTYPE DHT22   // DHT 22  (AM2302), AM2321
DHT dht(DHTPIN, DHTTYPE);

const char* ssid = "YOUR_SSID";
const char* password = "YOUR_SSID_PASSWORD!";
const char* mqtt_server = "YOUR_MQTT_SERVER_IP";

WiFiClient espClient;
PubSubClient client(espClient);

char inChar;
String inString;
long now = millis();
long lastMeasure = 0;

void setup_wifi() {
  delay(10);
  // We start by connecting to a WiFi network
  Serial.println();
  Serial.print("Connecting to ");
  Serial.print(ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.print("WiFi connected - ESP IP address: ");
  Serial.print(WiFi.localIP());
}

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

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

void setup() {

  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for (;;); // Don't proceed, loop forever
  }
  display.clearDisplay();
  dht.begin();
  Serial.begin(115200);
  setup_wifi();
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
}

void displayOled() {

  // Read humidity
  float h = dht.readHumidity();
  // Read temperature as Celsius (the default)
  float t = dht.readTemperature();
  // Read temperature as Fahrenheit (isFahrenheit = true)
  float f = dht.readTemperature(true);
  // Compute heat index in Fahrenheit (the default)
  float hif = dht.computeHeatIndex(f, h);
  // Compute heat index in Celsius (isFahreheit = false)
  float hic = dht.computeHeatIndex(t, h, true);

  display.clearDisplay();
  display.setTextColor(WHITE);
  display.setTextSize(1);
  display.setCursor(5, 20);
  display.print("Humidity:");
  display.setCursor(80, 20);
  display.print(h);
  display.print("%");
  display.setCursor(5, 35);
  display.print("Temperature:");
  display.setCursor(80, 35);
  display.print(f);
  display.print((char)247); // degree symbol
  display.print("F");
  display.setCursor(5, 50);
  display.print("Heat Index:");
  display.setCursor(80, 50);
  display.print(hif);
  display.print((char)247); // degree symbol
  display.print("F");
  display.display();

}

void loop() {
  if (!client.connected()) {
    reconnect();
  }
  if(!client.loop())
    client.connect("Suite2");

  now = millis();
  // Publishes new temperature and humidity every 30 seconds
  if (now - lastMeasure > 5000) {
    lastMeasure = now;
    // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
    float h = dht.readHumidity();
    // Read temperature as Celsius (the default)
    float t = dht.readTemperature();
    // Read temperature as Fahrenheit (isFahrenheit = true)
    float f = dht.readTemperature(true);

    // Check if any reads failed and exit early (to try again).
    if (isnan(h) || isnan(t) || isnan(f)) {
      Serial.println("Failed to read from DHT sensor!");
      return;
    }
    
    float hif = dht.computeHeatIndex(f, h);
    static char heatIndex[7];
    dtostrf(hif, 6, 2, heatIndex);
    
    static char temperatureTemp[7];
    dtostrf(f, 6, 2, temperatureTemp);
    
    static char humidityTemp[7];
    dtostrf(h, 6, 2, humidityTemp);
    
    client.publish("suite2room/humidity",humidityTemp);
    client.publish("suite2room/temperature",temperatureTemp);
    client.publish("suite2room/heatIndex",heatIndex);
  // Wait a few seconds between measurements.
  delay(2000);

  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println(F("Failed to read from DHT sensor!"));
    return;
  }

  // Compute heat index in Celsius (isFahreheit = false)
//  float hic = dht.computeHeatIndex(t, h, true);

  displayOled();

  }
}