Temperature, Humidity and Weather Forecast with an ESP32

// code for an ESP32 with DHT21 sensor on port D2 using blynk app and an OLED.
//The code takes temp and hum averages every 5 minutes. It also measures battery voltage and calculates wifi signal every 5 minutes.
//For the SSD1306 OLED:used library Adafruit_SSD1306, version 1.2.9, using this example: https://gist.github.com/RuiSantosdotme/020c23f3b45132f755f39f37a536b780 . Read for more details here: https://rntlab.com/question/esp32-oled-ssd1306-issue/

#define BLYNK_PRINT Serial  //
#include <BlynkSimpleEsp32.h>
#include <DHT.h>
#include <NTPClient.h>  
#include <WiFi.h>
#include <WiFiUdp.h> 
#include <Wire.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_GFX.h>

#include <JSON_Decoder.h>
#include <DarkSkyWeather.h>
// Just using this library for unix time conversion
#include <Time.h>


#define DHTPIN 2                                           // port where DTH21 is connected
#define DHTTYPE DHT21                                       // I use DHT21, change to other DHT sensor if you use other one
DHT dht(DHTPIN, DHTTYPE);   // enabled DHT sensor

//oled:
#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 #4 (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
//SCL (22) and SDA (21) pins

#define TIME_OFFSET -3UL * 3600UL // UTC + -7 hour (-7 for MST time zone)
#define uS_TO_S_FACTOR 1000000

char auth[] = "XXXXX";         // Your Blynk authentication string
char ssid[] = "XXXXX";         // SSID (name) of your wifi
char pass[] = "XXXXX";         // your wifi password

// Dark Sky API Details, replace x's with your API key
String api_key = "XXXXX"; // Obtain this from your Dark Sky account

// Set both longitude and latitude to at least 4 decimal places
String latitude =  "XXXXX"; // 90.0000 to -90.0000 negative for Southern hemisphere 
String longitude = "XXXXX"; // 180.000 to -180.000 negative for West
String units = "si";  // See notes tab
String language = ""; // See notes tab

WiFiUDP ntpUDP;

NTPClient timeClient(ntpUDP, "ntp.colostate.edu",-3600*7, 60000);   // Google for the NTP server for your location and copy-paste it here

const int update_interval = 5;     // desired update/sample interval in minutes
int oldminutes = 99;

DS_Weather dsw; // Weather forecast library instance

// Attach virtual serial terminal to Virtual Pin V1
WidgetTerminal terminal(V2);


 float h ;
 float t ;

 float wifi_rssi;
 float battery;



// get WiFi Signal Strength https://www.mathworks.com/help/thingspeak/measure-arduino-wifi-signal-strength-with-esp32.html
int getStrength(int points){
    long rssi = 0;
    long averageRSSI = 0;
    for (int i=0;i < points;i++){
        rssi += WiFi.RSSI();
        delay(10);
    }
   averageRSSI = rssi/points;
   return averageRSSI;
}


//function to correct ADC, https://github.com/G6EJD/ESP32-ADC-Accuracy-Improvement-function
 double ReadVoltage(byte pin){
 double reading = analogRead(pin); // Reference voltage is 3v3 so maximum reading is 3v3 = 4095 in range 0 to 4095
 if(reading < 1 || reading > 4095) return 0;
 return -0.000000000009824 * pow(reading,3) + 0.000000016557283 * pow(reading,2) + 0.000854596860691 * reading + 0.065440348345433;
 return -0.000000000000016 * pow(reading,4) + 0.000000000118171 * pow(reading,3)- 0.000000301211691 * pow(reading,2)+ 0.001109019271794 * reading + 0.034143524634089;
  } 


//function for writing in the terminal widget from blynk  
// You can send commands from Terminal to your hardware. Just use
// the same Virtual Pin as your Terminal Widget
BLYNK_WRITE(V2)
{

  // from example from Blynk: if you type "Marco" into Terminal Widget - it will respond: "Polo:"
  if (String("password") == param.asStr()) {
    terminal.println("Want the wifi password?") ;
    terminal.println("Here it is: 'arduinolab'") ;
  } else {

    // Send it back
    terminal.print("You said:");
    terminal.write(param.getBuffer(), param.getLength());
    terminal.println();
  }

  // Ensure everything is sent
  terminal.flush();
}


void setup()
{
  Serial.begin(115200);                                       // Enabled serial debugging output
  Blynk.begin(auth, ssid, pass);                            // Connects to wifi and Blynk services

  Serial.println("awake");  


 if(WiFi.status() != WL_CONNECTED){                        // connect to WiFi
      int i = 0;
      Serial.println("");
      Serial.print("Attempting to connect to SSID: ");
      Serial.println(ssid);
      while(WiFi.status() != WL_CONNECTED){
      WiFi.begin(ssid, pass);   // Connect to WPA/WPA2 network. Change this line if using open or WEP network
      Serial.print(++i); Serial.print(' ');
      if (i>=9) {                                       // sleep after 9 attempts
      Serial.println("WiFi failed to connect - going to sleep");
      //esp_sleep_enable_timer_wakeup((wakeBoundary-60) * uS_TO_S_FACTOR);   // configure time to sleep, wakeup 60s early
      //esp_deep_sleep_start();
      }
      delay(5000);     
      } 
  }


//OLED
  // SSD1306_SWITCHCAPVCC = generate display voltage from 3.3V internally
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3C for 128x32
    Serial.println(F("SSD1306 allocation failed"));
    for(;;); // Don't proceed, loop forever
  }
  

 // Clear the terminal content
  terminal.clear();

  // This will print Blynk Software version to the Terminal Widget when
  // your hardware gets connected to Blynk Server
   terminal.println(F("Blynk v" BLYNK_VERSION ": Device started"));
   terminal.println(F("Type 'password' and get a reply"));
   terminal.println(F("-------------"));
   terminal.flush();


  timeClient.begin();              // ntp client
  dht.begin();        //initialize sensor

}



void loop()
{

  Blynk.run();   // run blynk

 while(!timeClient.update()) {           // update NTP if needed
    timeClient.forceUpdate();
  }
   
  int hours=timeClient.getHours();        // update time variables
  int minutes=timeClient.getMinutes();
  int seconds=timeClient.getSeconds();
  int epoch=timeClient.getEpochTime();
  
//  if (hours==12 && minutes==0 && seconds==0) { // force update timeClient at noon, only use if always on, no sleep
//    timeClient.update(); 
//  }


  if ((minutes%update_interval==0) && (minutes != oldminutes)) {      // update loop
       oldminutes=minutes;

printCurrentWeather();//  // We can make 1000 requests a day
//  delay(5 * 60 * 1000); // Every 5 minutes = 288 requests per day

h = dht.readHumidity(); 
t = dht.readTemperature(); // read sensor  

wifi_rssi = getStrength(7);     // get wifi strength 
battery = ReadVoltage(35)*2.0;   // read battery volt, A13 for huzzah32, 35 for D32, , must mult by 2 for volt divider
   

  
  
Serial.print("Humidity: ");
Serial.println(h,2);
Serial.print("Temperature: ");  // prints a label
Serial.println(t,2);  
  
  
Serial.print("wifi strength: ");
Serial.println(wifi_rssi);
Serial.print("battery voltage: ");
Serial.println(battery);

Serial.println();        // carriage return after the last label


terminal.print("battery voltage: ");
terminal.println(battery);
terminal.print("wifi strength: ");
terminal.println(wifi_rssi);
terminal.flush();


                      
 
  }
}




/***************************************************************************************
**                          Send weather info to serial port
***************************************************************************************/
void printCurrentWeather()
{
  // Create the structures that hold the retrieved weather
  DSW_current *current = new DSW_current;
  DSW_hourly *hourly = new DSW_hourly;
  DSW_daily  *daily = new DSW_daily;

  time_t time;

  Serial.print("\nRequesting weather information from DarkSky.net... ");

  dsw.getForecast(current, hourly, daily, api_key, latitude, longitude, units, language);
  
  Serial.println("############### Current weather ###############\n");
  Serial.print("Current time             : "); Serial.print(strTime(current->time));
  Serial.print("Current temperature      : "); Serial.println(current->temperature);
  Serial.print("Current humidity         : "); Serial.println(current->humidity);
  Serial.print("Current pressure         : "); Serial.println(current->pressure);
  Serial.print("Current wind speed       : "); Serial.println(current->windSpeed);
 // Serial.print("Current wind gust        : "); Serial.println(current->windGust);
  //Serial.print("Current wind dirn        : "); Serial.println(current->windBearing);
 
 Serial.print("Current summary          : "); Serial.println(current->summary);
 // Serial.print("Current icon             : "); Serial.println(getMeteoconIcon(current->icon));
  Serial.print("Current precipInten      : "); Serial.println(current->precipIntensity);
//  Serial.print("Current precipType       : "); Serial.println(getMeteoconIcon(current->precipType));
  Serial.print("Current precipProbability: "); Serial.println(current->precipProbability);
  Serial.println();

Blynk.virtualWrite(4, String(current->temperature, 1));             // send to Blynk virtual pin 1 temperature value
Blynk.virtualWrite(5, current->humidity);                           // send to Blynk virtual pin 3 humidity value
Blynk.virtualWrite(1, String(t,1));                                 // send to Blynk virtual pin 1 temperature value
Blynk.virtualWrite(3, String(h,1));                                 // send to Blynk virtual pin 3 humidity value

//OLED display:
  display.clearDisplay();
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(0,0);  
  display.print("in T: ");
  display.println(t, 1);
  display.print("in H: ");
  display.println(h, 1);
  display.setCursor(0,21);
  display.setCursor(0,32);  
  display.print("out T:");
  display.println(current->temperature,1);
  display.print("out H:");
  display.println(current->humidity,1);
  display.setCursor(0,53);
  display.display();

terminal.println(F("-------------"));
terminal.print("Current precip Inten: ");
terminal.println(current->precipIntensity);
terminal.print("Current wind speed: ");
terminal.println(current->windSpeed);
terminal.println("");

Serial.println("############### Hourly weather  ###############\n");
 Serial.print("Overall hourly summary : "); Serial.println(hourly->overallSummary);
  for (int i = 0; i<MAX_HOURS; i++)
  {
Serial.print("Hourly summary  "); if (i<10) Serial.print(" ");
Serial.print(i);  Serial.print(" : "); Serial.println(hourly->summary[i]);
Serial.print("precipProbability  : "); Serial.println(hourly->precipProbability[i]);
//Serial.print("precipType         : "); Serial.println(hourly->precipType[i]);
// Serial.print("precipAccumulation : "); Serial.println(hourly->precipAccumulation[i]);
Serial.print("cloudCover         : "); Serial.println(hourly->cloudCover[i]);
Serial.println();
}

Serial.print("NextHour_precipProbability  : "); Serial.println(hourly->precipProbability[1]);
Serial.print("NextHour_cloudCover         : "); Serial.println(hourly->cloudCover[1]);
Serial.println();

  terminal.print("Next hour precip Probability: ");
  terminal.println(hourly->precipProbability[1]);
  terminal.print("Next hour cloud cover: ");
  terminal.println(hourly->cloudCover[1]);
  terminal.println("");


  Serial.println("###############  Daily weather  ###############\n");
  Serial.print("Daily summary     : "); Serial.println(daily->overallSummary);
  Serial.println();

  for (int i = 0; i<MAX_DAYS; i++)
  {
    Serial.print("Daily summary   ");
    Serial.print(i); Serial.print(" : "); Serial.println(daily->summary[i]);
    //Serial.print("time              : "); Serial.print(strTime(daily->time[i]));
    //Serial.print("sunriseTime       : "); Serial.print(strTime(daily->sunriseTime[i]));
    //Serial.print("sunsetTime        : "); Serial.print(strTime(daily->sunsetTime[i]));
    //Serial.print("Moon phase        : "); Serial.println(daily->moonPhase[i]);
    Serial.print("precipProbability : "); Serial.println(daily->precipProbability[i]);
    //Serial.print("precipType        : "); Serial.println(daily->precipType[i]);
    Serial.print("precipAccumulation: "); Serial.println(daily->precipAccumulation[i]);
        Serial.println();
  }

    Serial.print("today_precipAccumulation: "); Serial.println(daily->precipAccumulation[0]);
    Serial.print("today_precipProbability : "); Serial.println(daily->precipProbability[0]);
    Serial.print("Daily summary   ");Serial.println(daily->summary[0]);

 //terminal.print("today_precip Accumulation: ");
 //terminal.println(daily->precipAccumulation[0]);
 //terminal.print("today precip Probability: ");
 //terminal.println(daily->precipProbability[0]);
 //terminal.println("");

 terminal.print("today precip Accumulation: ");
 terminal.println(daily->precipAccumulation[0]);
 terminal.print("today precip Probability: ");
 terminal.println(daily->precipProbability[0]);
 terminal.print("today temperatureHigh: ");
 terminal.println(daily->temperatureHigh[0]);
 terminal.print("today temperatureLow: ");
 terminal.println(daily->temperatureLow[0]);
 terminal.print("Daily summary:  ");
 terminal.println(daily->summary[0]);
 terminal.println("");

  // Delete to free up space and prevent fragmentation as strings change in length
  delete current;
  delete hourly;
  delete daily;
}

/***************************************************************************************
**                          Convert unix time to a time string
***************************************************************************************/
String strTime(time_t unixTime)
{
  unixTime += TIME_OFFSET;
  return ctime(&unixTime);
}