int DHpin = 3; byte dat [5]; 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 |= (1 << (7-i)); // high front and low in the post while (digitalRead (DHpin) == HIGH); // data '1 ', wait for the next one receiver } } return data; } void start_test () { digitalWrite (DHpin, LOW); // put pin down and send start signal delay (30); // delay greater than 18ms, so DHT11 start signal can be detected digitalWrite (DHpin, HIGH); delayMicroseconds (40); // Waiting for the sensor's response pinMode (DHpin, INPUT); while (digitalRead (DHpin) == HIGH); delayMicroseconds (80); // DHT11 response and pulled the pin 80us if (digitalRead (DHpin) == LOW); delayMicroseconds (80); // DHT11 80us after the pin has been pulled down to start sending data for (int i = 0; i < 4; i ++) // receive temperature and humidity data raw data while parity is not considered dat[i] = read_data (); pinMode (DHpin, OUTPUT); digitalWrite (DHpin, HIGH); // send data once after releasing the pin, wait for the host to open the next Start signal } void setup () { Serial.begin (9600); pinMode (DHpin, OUTPUT); Serial.println("Testing the DHT11 sensor"); } void loop () { start_test (); Serial.print ("Current humdity ="); Serial.print (dat [0], DEC); // display the humidity-bit integer; Serial.print ('.'); Serial.print (dat [1], DEC); // display the humidity decimal places; Serial.println ('%'); Serial.print ("Current temperature ="); Serial.print (dat [2], DEC); // display the temperature of integer bits; Serial.print ('.'); Serial.print (dat [3], DEC); // display the temperature of decimal places; Serial.println ('C'); delay (700); }