dht22.cpp

#ifndef DHT22_h
#define DHT22_h

#define DHTLIB_OK               0
#define DHTLIB_ERROR_CHECKSUM   -1
#define DHTLIB_ERROR_TIMEOUT    -2
#define DHTLIB_INVALID_VALUE    -999
#define TIMEOUT 10000



class ClassDHT22 {
    public:
        int temperature();
        unsigned int humidity();
        uint8_t bits[5];  // buffer to receive data
        int read(uint8_t pin);
};

ClassDHT22 DHT22 = ClassDHT22();




int ClassDHT22::temperature() {
    return word(bits[2]&0x7F, bits[3]);
}




unsigned int ClassDHT22::humidity() {
    return word(bits[0], bits[1]);
}


int ClassDHT22::read(uint8_t pin) {
    uint8_t cnt = 7;
    uint8_t idx = 0;

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

    // REQUEST SAMPLE
    pinMode(pin, OUTPUT);
    digitalWrite(pin, LOW);
    delay(20);
    digitalWrite(pin, HIGH);
    delayMicroseconds(40);
    pinMode(pin, INPUT);

    // GET ACKNOWLEDGE or TIMEOUT
    unsigned int loopCnt = TIMEOUT;
    while(digitalRead(pin) == LOW)
        if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;

    loopCnt = TIMEOUT;
    while(digitalRead(pin) == HIGH)
        if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;

    // READ THE OUTPUT - 40 BITS => 5 BYTES
    for (int i=0; i<40; i++) {
        loopCnt = TIMEOUT;
        while(digitalRead(pin) == LOW) {
            if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
        }

        unsigned long t = micros();

        loopCnt = TIMEOUT;
        while(digitalRead(pin) == HIGH) {
            if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
        }


        if ((micros() - t) > 40) bits[idx] |= (1 << cnt);
        if (cnt == 0) {
            cnt = 7;   
            idx++;      
        }
        else cnt--;
    }

    return DHTLIB_OK;
}

#endif