SHT3x.cpp

#include "SHT3x.h"
		SHT3x::SHT3x(int Address, ValueIfError Value, uint8_t HardResetPin, SHT3xSensor SensorType, SHT3xMode Mode)
{
	_Error = noError;
	SetAddress((uint8_t)Address);
	_ValueIfError = Value;
	SetMode(Mode);
	_SensorType = SensorType;
	_HardResetPin = HardResetPin ;
	
}

void	SHT3x::Begin()
{
	Wire.begin(21,22);
	_OperationEnabled = true;
}

void	SHT3x::UpdateData()
{
	_Error = noError;
	if ((_LastUpdateMillisec == 0) || ((millis()-_LastUpdateMillisec)>=_UpdateIntervalMillisec))
	{
		SendCommand(_MeasMSB,_MeasLSB);
		if (_Error == noError)
		{
			Wire.requestFrom(_Address, (uint8_t)6);
			uint32_t WaitingBeginTime = millis();
			while ((Wire.available()<6) && ((millis() - WaitingBeginTime) < _TimeoutMillisec))
			{
				//Do nothing, just wait
			}
			if ((millis() - WaitingBeginTime) < _TimeoutMillisec)
			{
				_LastUpdateMillisec = WaitingBeginTime; 
				uint8_t data[6];
				for (uint8_t i = 0; i<6; i++)
				{
					data[i] = Wire.read();
				}
				
				if ((CRC8(data[0],data[1],data[2])) && (CRC8(data[3],data[4],data[5])))
				{
					uint16_t TemperatureRaw 	= (data[0]<<8)+(data[1]<<0);
					uint16_t RelHumidityRaw 	= (data[3]<<8)+(data[4]<<0);
					_TemperatureCeil =	((float) TemperatureRaw) * 0.00267033 - 45.;
					_TemperatureCeil =	_TemperatureCeil*_TemperatureCalibration.Factor +
										_TemperatureCalibration.Shift;
					_RelHumidity =	((float) RelHumidityRaw) * 0.0015259;
					_RelHumidity =	_RelHumidity * _RelHumidityCalibration.Factor +
									_RelHumidityCalibration.Shift;
					
					_Error = noError;
				}
				else
				{
					_Error = DataCorrupted;
				}
			} 
			else //Timeout
			{
				_Error = Timeout;
			}
		} 
		else //Error after message send
		{
			// Nothing to do, measurement commands will return NULL because of Error != noError
		}	
	}
	else //LastUpdate was too recently
	{
		//Nothing to do, wait for next call
	}
}

float	SHT3x::GetTemperature(TemperatureScale Degree)
{
	//default scale is Celsius
	//At first, calculate in Celsius, than, if need, recalculate to Farenheit or Kelvin and than adjust according to calibration;
	float Temperature = _TemperatureCeil;
	if (Degree == Kel)
	{
		Temperature+=273.15;
	}
	else if (Degree == Far)
	{
		Temperature = Temperature*1.8+32.;
	}

	return ReturnValueIfError(Temperature);
}

float	SHT3x::GetRelHumidity()
{
	return ReturnValueIfError(_RelHumidity);
}

float	SHT3x::GetAbsHumidity(AbsHumidityScale Scale)
{
	float 	millikelvins = GetTemperature(Kel) / 1000.;
	float 	Pressure = 0.;
	for (uint8_t i = 0; i<6; i++)
	{
		float term = 1.;
		for (uint8_t j = 0; j<i; j++)
		{
			term *= millikelvins;
		}
		Pressure += term*_AbsHumPoly[i];
	}
	Pressure *= GetRelHumidity();
	switch (Scale)
	{
		case mmHg:
		{
			//Already in mm Hg
			break;
		}
		case Torr:
		{
			//Already in Torr
			break;
		}
		case Pa:
		{
			Pressure *= 133.322;
			break;
		}
		case Bar:
		{
			Pressure *= 0.0013332;
			break;
		}
		case At:
		{
			Pressure *= 0.0013595;
			break;
		}
		case Atm:
		{
			Pressure *= 0.0013158;
			break;
		}
		case mH2O:
		{
			Pressure *= 0.013595;
			break;
		}
		case psi:
		{
			Pressure *= 0.019337;
			break;
		}
		default:
		{
			break;
		}
	}
	return ReturnValueIfError(Pressure);
}

float 	SHT3x::GetTempTolerance(TemperatureScale Degree, SHT3xSensor SensorType)
{
	//Temperature tolerance is similar for both SHT30 and SHT31
	//At first, calculate at Celsius (similar to Kelvins), than, if need, recalculate to Farenheit
	float Temperature = GetTemperature();
	float Tolerance;
	switch (SensorType)
	{
		case SHT30:
		{
			if ((0. <= Temperature) && (Temperature <= 65.))
			{	
				Tolerance = 0.2;
			}
			else if (Temperature > 65.)
			{
				//Linear from 0.2 at 65 C to 0.6 at 125 C.
				Tolerance = 0.0067 * Temperature - 0.2333;
			}
			else //if (Temperature < 0.)
			{
				//Linear from 0.6 at -40 C to 0.2 at 0 C.
				Tolerance = -0.01 * Temperature + 0.2;
			}
			break;
		}
		case SHT31:
		{
			if ((0. <= Temperature) && (Temperature <= 90.))
			{	
				Tolerance = 0.2;
			}
			else if (Temperature > 65.)
			{
				//Linear from 0.2 at 90 C to 0.5 at 125 C.
				Tolerance = 0.0086 * Temperature - 0.5714;
			}
			else //if (Temperature < 0.)
			{
				//Linear from 0.3 at -40 C to 0.2 at 0 C.
				Tolerance = -0.0025 * Temperature + 0.2;
			}
			break;
		}
		case SHT35:
		{
			if (Temperature <= 0.)
			{	
				Tolerance = 0.2;
			}
			else if ((0. < Temperature) && (Temperature <= 20.))
			{
				//Linear from 0.2 at 0 C to 0.1 at 20 C.
				Tolerance = -0.005 * Temperature + 0.2;
			}
			else if ((20. < Temperature) && (Temperature <= 60.))
			{
				Tolerance = 0.1;
			}
			else if ((60. < Temperature) && (Temperature <= 90.))
			{
				//Linear from 0.1 at 60 C to 0.2 at 90 C.
				Tolerance = -0.0033 * Temperature - 0.1;
			}
			else //if (90. < Temperature)
			{
				//Linear from 0.2 at 90 C to 0.4 at 125 C.
				Tolerance = 0.0057 * Temperature - 0.3143;
			}
			break;
		}
	}
	if (Degree == Far)
	{
		Tolerance *= 1.8;
	}
	

	return ReturnValueIfError(Tolerance);	
}

float 	SHT3x::GetRelHumTolerance(SHT3xSensor SensorType)
{
	float RelHumidity = GetRelHumidity();
	float Tolerance;
	switch (SensorType)
	{
		case SHT30:
		{
			if ((10.<= RelHumidity) && (RelHumidity <= 90.))
			{
				Tolerance =  2.;
			}
			else if (RelHumidity < 10.)
			{
				//Linear from 4 at 0% to 2 at 10%
				Tolerance = -0.2 * RelHumidity + 4.;
			}
			else
			{
				//Linear from 2 at 90% to 4 at 100%
				Tolerance =  0.2 * RelHumidity - 16.;
			}
			break;
		}
		case SHT31:
		{
			Tolerance = 2.;
			break;
		}
		case SHT35:
		{
			if (RelHumidity <= 80.)
			{
				Tolerance = 1.5;
			}
			else //if (80 < RelHumidity)
			{
				//Linear from 0.5 at 80% to 2 at 100%
				Tolerance = 0.025 * RelHumidity - 0.5;
			}
			break;	
		}
	}
	return ReturnValueIfError(Tolerance);

}

float 	SHT3x::GetAbsHumTolerance(AbsHumidityScale Scale, SHT3xSensor SensorType)
{
	/*	Dependence of absolute humidity is similar (from 0 to 80C) to P = H*a*exp(b*T),
	*	where P is absolute humidity, H is relative humidity, T is temperature (Celsius),
	*	a ~= 0.0396, b~=0.0575. 
	*	So its relative tolerance dP/P =  square root  [ (dH/H)^2 + (b*dT)^2 ].
	*/
	
	float RelHumidityRelTolerance = GetRelHumTolerance(SensorType)/GetRelHumidity();
	float TemperatureRelTolerance = 0.0575*GetTempTolerance(Cel, SensorType);
	RelHumidityRelTolerance*=RelHumidityRelTolerance;
	TemperatureRelTolerance*=TemperatureRelTolerance;
	return	ReturnValueIfError(
			GetAbsHumidity(Scale) * sqrt(RelHumidityRelTolerance+TemperatureRelTolerance)
			);
}

void	SHT3x::SetMode(SHT3xMode Mode)
{
	switch (Mode)
	{
		case Single_HighRep_ClockStretch:
		{
			_MeasMSB=0x2C;
			_MeasLSB=0x06;
			break;
		}
		case Single_MediumRep_ClockStretch:
		{
			_MeasMSB=0x2C;
			_MeasLSB=0x0D;
			break;
		}
		case Single_LowRep_ClockStretch:
		{
			_MeasMSB=0x2C;
			_MeasLSB=0x10;
			break;
		}
		case Single_HighRep_NoClockStretch:
		{
			_MeasMSB=0x24;
			_MeasLSB=0x00;
			break;
		}
		case Single_MediumRep_NoClockStretch:
		{
			_MeasMSB=0x24;
			_MeasLSB=0x0B;
			break;
		}
		case Single_LowRep_NoClockStretch:
		{
			_MeasMSB=0x24;
			_MeasLSB=0x16;
			break;
		}
		default:
		{
			_MeasMSB=0x2C;
			_MeasLSB=0x06;
			break;
		}
		
	}
}

void	SHT3x::SetTemperatureCalibrationFactors(CalibrationFactors TemperatureCalibration)
{
	_TemperatureCalibration = TemperatureCalibration;
}

void	SHT3x::SetRelHumidityCalibrationFactors(CalibrationFactors RelHumidityCalibration)
{
	_RelHumidityCalibration = RelHumidityCalibration;
}

void	SHT3x::SetTemperatureCalibrationPoints(CalibrationPoints SensorValues, CalibrationPoints Reference)
{
	_TemperatureCalibration.Factor = (Reference.Second - Reference.First) / (SensorValues.Second - SensorValues.First);
	_TemperatureCalibration.Shift = Reference.First - _TemperatureCalibration.Factor * SensorValues.First;
}

void	SHT3x::SetRelHumidityCalibrationPoints(CalibrationPoints SensorValues, CalibrationPoints Reference)
{
	_RelHumidityCalibration.Factor = (Reference.Second - Reference.First) / (SensorValues.Second - SensorValues.First);
	_RelHumidityCalibration.Shift = Reference.First - _RelHumidityCalibration.Factor * SensorValues.First;
}

void 	SHT3x::SoftReset()
{
	SendCommand(0x30, 0xA2);
}

void	SHT3x::HardReset()
{
	if (_HardResetPin<100) //MEGA2560 have only 68 pins
	{
		pinMode(_HardResetPin,OUTPUT);
		digitalWrite(_HardResetPin,LOW);
		delayMicroseconds(1); //Reset pin have to be LOW at least 350ns, so 1 usec is enough. I think, there is no need for micros() for 1 usec.
		digitalWrite(_HardResetPin,HIGH);
	}
}

void	SHT3x::HeaterOn()
{
	SendCommand(0x30, 0x6D);
}

void	SHT3x::HeaterOff()
{
	SendCommand(0x30, 0x66);
}

void	SHT3x::SetAddress(uint8_t Address)
{
	if ((Address == 0x44) || (Address == 0x45))
	{
		_Address = Address;
	}
	else
	{
		_Error = WrongAddress;
	}
}

void	SHT3x::SetUpdateInterval(uint32_t UpdateIntervalMillisec)
{
	if (UpdateIntervalMillisec > 0)
	{
		_UpdateIntervalMillisec = UpdateIntervalMillisec;
	}
}

void	SHT3x::SetTimeout(uint32_t TimeoutMillisec)
{
	if (TimeoutMillisec > 0)
	{
		_TimeoutMillisec = _TimeoutMillisec;
	}
}

void 	SHT3x::I2CError(uint8_t I2Canswer)
{
				switch (I2Canswer)
			{
				case 0:
				{
					_Error = noError;
					break;
				}
				case 1:
				{
					_Error = TooMuchData;
					break;
				}
				case 2:
				{
					_Error = AddressNACK;
					break;
				}
				case 3:
				{
					_Error = DataNACK;
					break;
				}
				case 4:
				{
					_Error = OtherI2CError;
					break;
				}
				default:
				{
					_Error = UnexpectedError;
					break;
				}
			}
}

void 	SHT3x::SendCommand(uint8_t MSB, uint8_t LSB)
{
	if (_OperationEnabled)
	{
		//Everything is OK, nothing to do
	}
	else 
	{
		Wire.begin();
		_OperationEnabled = true;
	}
	Wire.beginTransmission(_Address);
	// Send Soft Reset command
	Wire.write(MSB);
	Wire.write(LSB);
	// Stop I2C transmission
	uint8_t success = Wire.endTransmission();
}

bool 	SHT3x::CRC8(uint8_t MSB, uint8_t LSB, uint8_t CRC)
{
	/*
	*	Name  : CRC-8
	*	Poly  : 0x31	x^8 + x^5 + x^4 + 1
	*	Init  : 0xFF
	*	Revert: false
	*	XorOut: 0x00
	*	Check : for 0xBE,0xEF CRC is 0x92
	*/
	uint8_t crc = 0xFF;
	uint8_t i;
	crc ^=MSB;

		for (i = 0; i < 8; i++)
			crc = crc & 0x80 ? (crc << 1) ^ 0x31 : crc << 1;

	crc ^= LSB;
	for (i = 0; i < 8; i++)
				crc = crc & 0x80 ? (crc << 1) ^ 0x31 : crc << 1;

	if (crc==CRC)
	{
		return true;
	}
	else
	{
		return false;
	}
}

uint8_t	SHT3x::GetError()
{
	return _Error;
}

float	SHT3x::ReturnValueIfError(float Value)
{
	if (_Error == noError)
	{
		return Value;
	}
	else
	{
		if (_ValueIfError == PrevValue)
		{
			return Value;
		}
		else
		{
			return 0.;
		}
	}
}

void	SHT3x::ToReturnIfError(ValueIfError Value)
{
	_ValueIfError = Value;
}