/*
  Abundance DHT

 Based on:
 https://www.electronicwings.com/avr-atmega/dht11-sensor-interfacing-with-atmega16-32

 modified 126 June 2021
 by Jean-Luc Pierite

*/

//KY015 DHT11 Temperature and humidity sensor 
int DHpin = 21;

uint8_t I_RH,D_RH,I_Temp,D_Temp,CheckSum;

byte read_data () {
  byte _data;
  for (int i = 0; i < 8; i ++) {
    if (digitalRead (DHpin) == LOW) {
      while (digitalRead (DHpin) == LOW); // wait for 50us
      delayMicroseconds (30); // determine the duration of the high level to determine the data is '0 'or '1'
      if (digitalRead (DHpin) == HIGH)
        _data = (_data<<1)|(0x01);  /* then its logic HIGH */
      else      /* otherwise its logic LOW */
        _data = (_data<<1);
      while (digitalRead (DHpin) == HIGH); // data '1 ', wait for the next one receiver
     }
  }
return _data;
}
 
void start_test () {
// Request
  pinMode (DHpin, OUTPUT);
  digitalWrite (DHpin, LOW); // bus down, send start signal
  delay (20); // delay greater than 18ms, so DHT11 start signal can be detected
  digitalWrite (DHpin, HIGH);

  // Response
  pinMode (DHpin, INPUT);
  while (digitalRead (DHpin) == HIGH);
  while (digitalRead (DHpin) == LOW);
  while (digitalRead (DHpin) == HIGH);

  I_RH = read_data();  /* store first eight bit in I_RH */
  D_RH = read_data();  /* store next eight bit in D_RH */
  I_Temp = read_data();  /* store next eight bit in I_Temp */
  D_Temp = read_data();  /* store next eight bit in D_Temp */
  CheckSum = read_data();
  
}

void setup() {
  Serial.begin (9600);
  delay(2000); // unstable period
}

void loop() {

  start_test ();
  
if ((I_RH + D_RH + I_Temp + D_Temp) != CheckSum)
{
  Serial.println ("parity failed");
} else {
  Serial.print ("Current humdity = ");
  Serial.print (I_RH, DEC); // display the humidity-bit integer;
  Serial.print ('.');
  Serial.print (D_RH, DEC); // display the humidity decimal places;
  Serial.println ('%');
  Serial.print ("Current temperature = ");
  Serial.print (I_Temp, DEC); // display the temperature of integer bits;
  Serial.print ('.');
  Serial.print (D_Temp, DEC); // display the temperature of decimal places;
  Serial.println ('C');
}
  delay (5000);
}