/*	https://wokwi.com/projects/406690699742710785
    https://journals.ametsoc.org/view/journals/bams/86/2/bams-86-2-225.xml


Td = t - ((100 - RH)/5.) 
where Td is dew point temperature (in degrees Celsius), 
      t is observed temperature (in degrees Celsius), 
and   RH is relative humidity (in percent). 
Apparently this relationship is fairly accurate for relative humidity values above 50%.
*/

#include <DHT22.h>
#include <LCD-I2C.h>

//define pin data
#define pinDATA A0 // SDA, or almost any other I/O pin
DHT22 dht22(pinDATA); 

LCD_I2C lcd(0x27, 16, 2); // Default address of most PCF8574 modules, change according


  float  t;
  float RH;
  float Td;
 
void setup() {
  Serial.begin(9600); //1bit=10µs
  Serial.println("\Simulation DTH22");

  lcd.begin();
    lcd.display();
    lcd.backlight();
    
  lcd.setCursor(0, 0);
  lcd.print("Simulation DTH22");

  delay(3000);

}

void loop() {
 //   Serial.println(dht22.debug()); //optionnal

 
   t = dht22.getTemperature() ;
  RH = dht22.getHumidity()    ;
  Td = t - ((100 - RH)/5)     ;


  if (dht22.getLastError() != dht22.OK)   {
    Serial.print("last error :");
    Serial.println(dht22.getLastError()); }

  Serial.print("RH=");  Serial.print(RH,1);   Serial.print("\t");
  Serial.print("t=");   Serial.print(t,1);    Serial.print("\t");
  Serial.print("DP=");Serial.println(Td,1);

  lcd.clear();
  lcd.setCursor(0, 0);  lcd.print("RH=");  lcd.print(RH,1);
  lcd.setCursor(8, 0);  lcd.print("t=");  lcd.print(t,1);
  lcd.setCursor(0, 1);  lcd.print("DP=");  lcd.print(Td,1);
 

  delay(2000); //Collecting period should be : >1.7 second
  
}