Using the DHT11 temp/hum sensor

Using Arduino Programming Questions
1

HI everyone,

I just get this example for the DHT11 sensor and add some problem reading is output.

This is my code

double humidity;
double temperature;


void setup()
{
  Serial.begin(115200);
  Serial.println("DHT11 TEST PROGRAM ");

}


void loop()
{
  read_dht11();
  
}

void read_dht11(void){
  
  	// BUFFER TO RECEIVE
	uint8_t bits[5];
	uint8_t cnt = 7;
	uint8_t idx = 0;

        // EMPTY BUFFER
	for (int i=0; i< 5; i++) bits[i] = 0;

	// REQUEST SAMPLE
	pinMode(22, OUTPUT);
	digitalWrite(22, LOW);
	delay(18);
	digitalWrite(22, HIGH);
	delayMicroseconds(40);
	pinMode(22, INPUT);

	// ACKNOWLEDGE or TIMEOUT
	unsigned int loopCnt = 10000;
	while(digitalRead(22) == LOW)
		if (loopCnt-- == 0)
                {
                  Serial.println("Error time out 1");
                }
        Serial.println("Passe 1");
	loopCnt = 10000;
	while(digitalRead(22) == HIGH)
		if (loopCnt-- == 0)
                {
                    Serial.println("Error time out 2");
                }
        Serial.println("Passe 2");
	// READ OUTPUT - 40 BITS => 5 BYTES or TIMEOUT
	for (int i=0; i<40; i++)
	{
		loopCnt = 10000;
		while(digitalRead(22) == LOW)
			if (loopCnt-- == 0)
                        {
                            Serial.println("Error time out 3");
                        }
                Serial.println("Passe 3");
		unsigned long t = micros();

		loopCnt = 10000;
		while(digitalRead(22) == HIGH)
			if (loopCnt-- == 0)
                        {
                            Serial.println("Error time out 4");
                        }
                Serial.println("Passe 4");
		if ((micros() - t) > 40) bits[idx] |= (1 << cnt);
		if (cnt == 0)   // next byte?
		{
			cnt = 7;    // restart at MSB
			idx++;      // next byte!
                        Serial.println("Count = 0");
		}
		else cnt--;
                Serial.println("Count --");
	}

	// WRITE TO RIGHT VARS
        // as bits[1] and bits[3] are allways zero they are omitted in formulas.
	humidity    = bits[0]; 
	temperature = bits[2]; 

	uint8_t sum = bits[0] + bits[2];  

	if (bits[4] != sum) 
        {
            Serial.println("Checksum error");
        }
	 Serial.println("OK");

}

And this is why I get for troubleshooting on the serial monitor

DHT11 TEST PROGRAM 
Passe 1
Passe 2
Passe 3
Passe 4
Count --
Passe 3
Passe 4
Count --
Passe 3
Passe 4
Count --
Passe 3
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4
Error time out 4

Is some of you have already worked with this sensor??

At first it seems to work, but after couple of iteration....error 4, error 4, error 4....

Thanks in advance!

2

You are reading the Sensor too quickly.
The sensor has maximum reading rate of once every 2 seconds.
Put some delay in your reading loop.