Connect the Temperature and Humidity sensor .Then you can use the following programme to gain the temperature and humidity of the environment.







#define DHT11_PIN 0 // ADC0   

byte read_dht11_dat() 

{ byte i = 0; 

  byte result=0; 

  for(i=0; i< 8; i++)

  {     

      while(!(PINC & _BV(DHT11_PIN))); // wait for 50us delayMicroseconds(30);   

      if(PINC & _BV(DHT11_PIN)) result |=(1<<(7-i)); 

      while((PINC & _BV(DHT11_PIN))); // wait '1' finish     

   } 

   return result; 

}     

 

void setup() 

{ 

DDRC |= _BV(DHT11_PIN); 

PORTC |= _BV(DHT11_PIN);   

Serial.begin(9600);   

Serial.println("Ready"); 

}

 

void loop() 

{ 

 byte dht11_dat[5];

 byte dht11_in;

 byte i; // start condition 

 // 1. pull-down i/o pin from 18ms

 PORTC &= ~_BV(DHT11_PIN); 

 delay(18); 

 PORTC |= _BV(DHT11_PIN); 

 delayMicroseconds(40); 

 DDRC &= ~_BV(DHT11_PIN);

 delayMicroseconds(40);

 dht11_in = PINC & _BV(DHT11_PIN);

 if(dht11_in)

 {

   Serial.println("dht11 start condition 1 not met"); 

   return; 

  } 

 delayMicroseconds(80);  

 dht11_in = PINC & _BV(DHT11_PIN);  

 if(!dht11_in)

 { 

   Serial.println("dht11 start condition 2 not met");

   return;

 } 

 delayMicroseconds(80); // now ready for data reception 

 for (i=0; i<5; i++) 

   dht11_dat[i] = read_dht11_dat();   

 DDRC |= _BV(DHT11_PIN); 

 PORTC |= _BV(DHT11_PIN); 

 byte dht11_check_sum = dht11_dat[0]+dht11_dat[1]+dht11_dat[2]+dht11_dat[3]; 

 if(dht11_dat[4]!= dht11_check_sum) 

 { 

  Serial.println("DHT11 checksum error"); 

 }   

 Serial.print("Current humdity = "); 

 Serial.print(dht11_dat[0], DEC);

 Serial.print(".");

 Serial.print(dht11_dat[1], DEC);

 Serial.print("% ");

 Serial.print("temperature = ");

 Serial.print(dht11_dat[2], DEC);

 Serial.print(".");

 Serial.print(dht11_dat[3], DEC);

 Serial.println("C ");

 delay(2000);

}