/**
* Temperature Request
*/
void SHT1x::requestTemperature()
{
int _val;
// Command to send to the SHT1x to request Temperature
int _gTempCmd = 0b00000011;
sendCommandSHT(_gTempCmd, _dataPin, _clockPin);
}
/**
* Reads current temperature-corrected relative humidity
*/
float SHT1x::readHumidity()
{
int _val; // Raw humidity value returned from sensor
float _linearHumidity; // Humidity with linear correction applied
float _correctedHumidity; // Temperature-corrected humidity
float _temperature; // Raw temperature value
// Conversion coefficients from SHT15 datasheet
const float C1 = -4.0; // for 12 Bit
const float C2 = 0.0405; // for 12 Bit
const float C3 = -0.0000028; // for 12 Bit
const float T1 = 0.01; // for 14 Bit @ 5V
const float T2 = 0.00008; // for 14 Bit @ 5V
// Command to send to the SHT1x to request humidity
int _gHumidCmd = 0b00000101;
// Fetch the value from the sensor
sendCommandSHT(_gHumidCmd, _dataPin, _clockPin);
waitForResultSHT(_dataPin);
_val = getData16SHT(_dataPin, _clockPin);
skipCrcSHT(_dataPin, _clockPin);
// Apply linear conversion to raw value
_linearHumidity = C1 + C2 * _val + C3 * _val * _val;
// Get current temperature for humidity correction
_temperature = readTemperatureC();
// Correct humidity value for current temperature
_correctedHumidity = _temperature * (T1 + T2 * _val) + _linearHumidity;
return (_correctedHumidity);
}
/**
* Reads the current raw temperature value
*/
uint16_t sensirion::readTemperatureRaw()
{
uint16_t _val;
// Command to send to the SHT1x to request Temperature
const uint8_t _gTempCmd = 0b00000011;
if (millis() - _lastTempMillis < SHT_CACHE_MILLIS ){
return _lastTempRaw;
} else {
if ( sendCommandSHT(_gTempCmd, _dataPin, _clockPin) == SHT_SUCCESS ){
waitForResultSHT(_dataPin);
_val = getData16SHT(_dataPin, _clockPin);
uint8_t rxcrc = rev8bits( readCRC(_dataPin, _clockPin ) );
uint8_t mycrc = crc8add( 0, _gTempCmd );
mycrc = crc8add( mycrc, _val );
if (mycrc != rxcrc){
Serial.println("SHT: crc error");
Serial.print(" Got: 0x"); Serial.println(rxcrc, HEX);
Serial.print(" Expected: 0x"); Serial.println(mycrc, HEX);
return 0;
}
// cache
_lastTempMillis = millis();
_lastTempRaw = _val;
return (_val);
}
}
return 0; // error
}
void SHT1x::requestHumidity(){
// Command to send to the SHT1x to request humidity
int _gHumidCmd = 0b00000101;
// Fetch the value from the sensor
sendCommandSHT(_gHumidCmd, _dataPin, _clockPin);
}
/**
* Reads current temperature-corrected relative humidity
*/
float sensirion::readHumidity()
{
uint16_t _val; // Raw humidity value returned from sensor
float _linearHumidity; // Humidity with linear correction applied
float _correctedHumidity; // Temperature-corrected humidity
float _temperature; // Raw temperature value
// Conversion coefficients from SHT15 datasheet
const float C1 = -4.0; // for 12 Bit
const float C2 = 0.0405; // for 12 Bit
const float C3 = -0.0000028; // for 12 Bit
const float T1 = 0.01; // for 14 Bit @ 5V
const float T2 = 0.00008; // for 14 Bit @ 5V
// Command to send to the SHT1x to request humidity
const uint8_t _gHumidCmd = 0b00000101;
// check cache
if ( millis() - _lastHumMillis < SHT_CACHE_MILLIS){
return _lastHumVal;
} else{
// Fetch the value from the sensor
if ( sendCommandSHT(_gHumidCmd, _dataPin, _clockPin) == SHT_SUCCESS ){
waitForResultSHT(_dataPin);
_val = getData16SHT(_dataPin, _clockPin);
uint8_t rxcrc = rev8bits( readCRC(_dataPin, _clockPin ) );
uint8_t mycrc = crc8add( 0, _gHumidCmd );
mycrc = crc8add( mycrc, _val );
if (mycrc != rxcrc){
Serial.println("SHT: crc error");
Serial.print(" Got: 0x"); Serial.println(rxcrc, HEX);
Serial.print(" Expected: 0x"); Serial.println(mycrc, HEX);
return NAN;
}
// Apply linear conversion to raw value
_linearHumidity = C1 + C2 * _val + C3 * _val * _val;
// Get current temperature for humidity correction
_temperature = readTemperatureC();
// Correct humidity value for current temperature
_correctedHumidity = (_temperature - 25.0 ) * (T1 + T2 * _val) + _linearHumidity;
// cache
_lastHumVal = _correctedHumidity;
_lastHumMillis = millis();
return (_correctedHumidity);
}
}
//error
return NAN;
}
/**
* Reads the current raw temperature value
*/
float SHT1x::readTemperatureRaw()
{
int _val;
// Command to send to the SHT1x to request Temperature
int _gTempCmd = 0b00000011;
sendCommandSHT(_gTempCmd, _dataPin, _clockPin);
waitForResultSHT(_dataPin);
_val = getData16SHT(_dataPin, _clockPin);
skipCrcSHT(_dataPin, _clockPin);
return (_val);
}
uint8_t sensirion::readStatus()
{
uint16_t _val;
// Command to send to the SHT1x to request Status
const uint8_t _gStatCmd = 0b00000111;
sendCommandSHT(_gStatCmd, _dataPin, _clockPin);
// result is immediate with read status.
//waitForResultSHT(_dataPin);
shtDelay(1);
_val = getData16SHT(_dataPin, _clockPin);
/*
// Send the required ack
digitalWrite(_dataPin, LOW);
pinMode(_dataPin, OUTPUT);
shtDelay(1);
digitalWrite(_clockPin, HIGH);
shtDelay(1);
digitalWrite(_clockPin, LOW);
shtDelay(1);
pinMode(_dataPin, INPUT);
*/
// end transmission, turn off gpio's
pinMode(_dataPin, INPUT);
pinMode(_clockPin, INPUT);
uint8_t rx_val = _val >> 8;
uint8_t rx_crc = _val & 0xff;
uint8_t local_crc = crc8add( 0, _gStatCmd );
local_crc = crc8add(local_crc, rx_val);
if (rx_crc != rev8bits(local_crc)){
Serial.println("SHT: crc error");
Serial.print(" Got: 0x"); Serial.println(rx_crc, HEX);
Serial.print(" Expected: 0x"); Serial.println(local_crc, HEX);
}
return rx_val;
}
