DHT.cpp

/*  DHT library

    MIT license
    written by Adafruit Industries
*/

#include <math.h>
#include "DHT.h"
//#define NAN 0
#ifdef DEBUG
    #define DEBUG_PRINT(...)  Serial.println(__VA_ARGS__)
#else
    #define DEBUG_PRINT(...)
#endif
DHT::DHT(uint8_t pin, uint8_t type, uint8_t count) {
    _pin = pin;
    _type = type;
    _count = count;
    firstreading = true;
}

DHT::DHT(uint8_t type) {
    _pin = 0;
    _type = type;
    _count = COUNT;
    firstreading = true;
    if (_type != DHT10){
        DEBUG_PRINT("Error : No pins are defined\n");
    }
}

void DHT::begin(void) {

    if (_type == DHT10) {
        if (DHT10Init()) {
            SERIALPRINT.println("Error : Failed to init DHT 11\n");
            while (1);
        }
    } else {
        // set up the pins!
        pinMode(_pin, INPUT);
        digitalWrite(_pin, HIGH);
        _lastreadtime = 0;
    }

}

/** Common  interface to get temp&humi value.support all DHT device.

    @return 0 for calibrated failed,1 for succeed.
 **/
int DHT::readTempAndHumidity(float* data) {
    uint32_t target_val[2] = {0};
    uint32_t cnt = 0;
    if (_type == DHT10) {
        while (DHT10ReadStatus() == 0) {
            DHT10Init();
            delay(30);
            cnt++;
            if (cnt > 3) {
                return -1;
            }
        }
        //wait for data ready。
        while (readTargetData(target_val)) {
            cnt++;
            delay(50);
            if (cnt > 5) {
                return -1;
            }

        }
        data[0] = target_val[0] * 100.0 / 1024 / 1024;
        data[1] = target_val[1] * 200.0 / 1024 / 1024 - 50;

    } else {
        data[0] = readHumidity();
        data[1] = readTemperature();
        if (isnan(data[0]) || isnan(data[1])) {
            return -1;
        }
    }
    return 0;
}

//boolean S == Scale.  True == Farenheit; False == Celcius
float DHT::readTemperature(bool S) {
    if(_type == DHT10){
		float temp[2];
		readTempAndHumidity(temp);
		if (S) {
			temp[1] = convertCtoF(temp[1]);
		}
		return temp[1];
	}
	else{
		float f;
		if (read()) {
			switch (_type) {
				case DHT11:
					f = data[2];
					if(data[3]%128<10){
						f += data[3]%128/10.0f;
					}else if(data[3]%128<100){
						f += data[3]%128/100.0f;
					}else{
						f += data[3]%128/1000.0f;
					}
					if(data[3]>=128){ // The left-most digit indicate the negative sign. 
						f = -f;
					}
					if (S) {
						f = convertCtoF(f);
					}

					return f;
				case DHT22:
				case DHT21:
					f = data[2] & 0x7F;
					f *= 256;
					f += data[3];
					f /= 10;
					if (data[2] & 0x80) {
						f *= -1;
					}
					if (S) {
						f = convertCtoF(f);
					}

					return f;
			}
		}
	}
    DEBUG_PRINT("Read fail");
    return NAN;
}

float DHT::convertCtoF(float c) {
    return c * 9 / 5 + 32;
}

float DHT::readHumidity(void) {
    if(_type == DHT10){
		float temp[2];
		readTempAndHumidity(temp);
		return temp[0];
	}
	else{
		float f;
		if (read()) {
			switch (_type) {
				case DHT11:
					f = data[0];
					return f;
				case DHT22:
				case DHT21:
					f = data[0];
					f *= 256;
					f += data[1];
					f /= 10;
					return f;
			}
		}
	}
    DEBUG_PRINT("Read fail");
    return NAN;
}


boolean DHT::read(void) {
    uint8_t laststate = HIGH;
    uint8_t counter = 0;
    uint8_t j = 0, i;
    unsigned long currenttime;

    // pull the pin high and wait 250 milliseconds
    digitalWrite(_pin, HIGH);
    delay(250);

    currenttime = millis();
    if (currenttime < _lastreadtime) {
        // ie there was a rollover
        _lastreadtime = 0;
    }
    if (!firstreading && ((currenttime - _lastreadtime) < 2000)) {
        return true; // return last correct measurement
        //delay(2000 - (currenttime - _lastreadtime));
    }
    firstreading = false;
    /*
        DEBUG_PRINT("Currtime: "); DEBUG_PRINT(currenttime);
        DEBUG_PRINT(" Lasttime: "); DEBUG_PRINT(_lastreadtime);
    */
    _lastreadtime = millis();

    data[0] = data[1] = data[2] = data[3] = data[4] = 0;

    // now pull it low for ~20 milliseconds
    pinMode(_pin, OUTPUT);
    digitalWrite(_pin, LOW);
    delay(20);
    //cli();
    digitalWrite(_pin, HIGH);
    delayMicroseconds(20);
    pinMode(_pin, INPUT);

    // read in timings
    for (i = 0; i < MAXTIMINGS; i++) {
        counter = 0;
        while (digitalRead(_pin) == laststate) {
            counter++;
            delayMicroseconds(1);
            if (counter == 255) {
                break;
            }
        }
        laststate = digitalRead(_pin);

        if (counter == 255) {
            break;
        }

        // ignore first 3 transitions
        if ((i >= 4) && (i % 2 == 0)) {
            // shove each bit into the storage bytes
            data[j / 8] <<= 1;
            if (counter > _count) {
                data[j / 8] |= 1;
            }
            j++;
        }

    }

    //sei();

    /*
        DEBUG_PRINTln(j, DEC);
        DEBUG_PRINT(data[0], HEX); DEBUG_PRINT(", ");
        DEBUG_PRINT(data[1], HEX); DEBUG_PRINT(", ");
        DEBUG_PRINT(data[2], HEX); DEBUG_PRINT(", ");
        DEBUG_PRINT(data[3], HEX); DEBUG_PRINT(", ");
        DEBUG_PRINT(data[4], HEX); DEBUG_PRINT(" =? ");
        DEBUG_PRINTln(data[0] + data[1] + data[2] + data[3], HEX);
    */

    // check we read 40 bits and that the checksum matches
    if ((j >= 40) &&
            (data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF))) {
        return true;
    }


    return false;

}

/*****************************************************************************/
/*****************************************************************************/

/** Reset sensor.
    @return 0 for calibrated failed,1 for succeed.
 **/
int DHT::DHT10Reset(void) {
    if (_type == DHT10) {
        return i2cWriteByte(RESET_REG_ADDR);
    } else {
        return 0;
        SERIALPRINT.println("This function only support for DHT10");
    }

}

/** Read status register.check the calibration flag - bit[3]: 1- calibrated ok ,0 - Not calibrated.

    @return 0 for calibrated failed,1 for succeed.

 **/
int DHT::DHT10ReadStatus(void) {

    int ret = 0;
    uint8_t statu = 0;
    if (_type == DHT10) {
        ret = i2cReadByte(statu);
        if (ret) {
            SERIALPRINT.println("Failed to read byte\n");
        }
        if ((statu & 0x8) == 0x8) {
            return 1;
        } else {
            return 0;
        }
    } else {
        SERIALPRINT.println("This function only support for DHT10");
        return 0;
    }

}

/** Init sensor,send 0x08,0x00 to register 0xe1.
    @ return : 0 if success, non-zero if failed.
 **/
int DHT::setSystemCfg(void) {
    uint8_t cfg_param[] = {0xe1, 0x08, 0x00};
    if (_type == DHT10) {
        return i2cWriteBytes(cfg_param, sizeof(cfg_param));
    } else {
        SERIALPRINT.println("This function only support for DHT10");
        return 0;
    }
}


/** Read temp & humi result buf from sensor.
    total 6 bytes,the first byte for status register,other 5 bytes for temp & humidity data.
    @ return : 0 if success, non-zero if failed.
 **/
int DHT::readTargetData(uint32_t* data) {
    uint8_t statu = 0;
    uint8_t bytes[6] = {0};
    uint8_t cfg_params[] = {0xac, 0x33, 0x00};
    //int ret = 0;

    if (_type == DHT10) {

        if (i2cWriteBytes(cfg_params, sizeof(cfg_params))) {
            return -1;
        }

        delay(75);
        // check device busy flag， bit[7]:1 for busy, 0 for idle.
        while ((statu & 0x80) == 0x80) {
            SERIALPRINT.println("Device busy!");
            delay(200);
            if (i2cReadByte(statu)) {
                return -1;
            }
        }

        if (i2cReadBytes(bytes, sizeof(bytes))) {
            return -1;
        }


        data[HUMIDITY_INDEX] = (data[HUMIDITY_INDEX] | bytes[1]) << 8;
        data[HUMIDITY_INDEX] = (data[HUMIDITY_INDEX] | bytes[2]) << 8;
        data[HUMIDITY_INDEX] = (data[HUMIDITY_INDEX] | bytes[3]);
        data[HUMIDITY_INDEX] = data[HUMIDITY_INDEX] >> 4;

        data[TEMPRATURE_INDEX] = (data[TEMPRATURE_INDEX] | bytes[3]) << 8;
        data[TEMPRATURE_INDEX] = (data[TEMPRATURE_INDEX] | bytes[4]) << 8;
        data[TEMPRATURE_INDEX] = (data[TEMPRATURE_INDEX] | bytes[5]);
        data[TEMPRATURE_INDEX] &= 0xfffff;

        return 0;
    } else {
        SERIALPRINT.println("This function only support for DHT10");
        return 0;
    }
}

/** DHT10 Init function.
    Reset sensor and wait for calibration complete.
    @ return : 0 if success, non-zero if failed.
 **/
int DHT::DHT10Init(void) {
    int ret = 0;
    int cnt = 0;

    if (_type == DHT10) {

        delay(500);
        DHT10Reset();
        delay(300);

        ret = setSystemCfg();
        if (ret) {
            SERIALPRINT.println("Failed to set system conf reg \n");
        }
        //SERIALPRINT.println("Set system cfg OK!");

        delay(500);

        while (DHT10ReadStatus() == 0) {
            SERIALPRINT.println("get status error!");
            DHT10Reset();
            delay(500);
            if (setSystemCfg()) {
                SERIALPRINT.println("Failed to set system conf reg \n");
            }
            delay(500);
            cnt++;
            if (cnt > 5) {
                return -1;
            }
        }
        return 0;
    } else {
        SERIALPRINT.println("This function only support for DHT10");
        return 0;
    }

}



/*****************************************************************************/
/*****************************************************************************/

int DHT::i2cReadByte(uint8_t& byte) {
    int cnt = 0;
    Wire.requestFrom(DEFAULT_IIC_ADDR, 1);
    while (1 != Wire.available()) {
        cnt++;
        if (cnt >= 10) {
            return -1;
        }
        delay(1);
    }

    byte = Wire.read();
    return 0;
}

int DHT::i2cReadBytes(uint8_t* bytes, uint32_t len) {
    int cnt = 0;
    Wire.requestFrom(DEFAULT_IIC_ADDR, len);
    while (len != (uint32_t) Wire.available()) {
        cnt++;
        if (cnt >= 10) {
            return -1;
        }
        delay(1);
    }
    for (uint32_t i = 0; i < len; i++) {
        bytes[i] = Wire.read();
    }
    return 0;
}


int DHT::i2cWriteBytes(uint8_t* bytes, uint32_t len) {
    Wire.beginTransmission(DEFAULT_IIC_ADDR);
    for (uint32_t i = 0; i < len; i++) {
        Wire.write(bytes[i]);
    }
    return Wire.endTransmission();
}

int DHT::i2cWriteByte(uint8_t byte) {
    Wire.beginTransmission(DEFAULT_IIC_ADDR);
    Wire.write(byte);
    return Wire.endTransmission();
}