Adafruit_BME280.cpp

/*!
 * @file Adafruit_BME280.cpp
 *
 * @mainpage Adafruit BME280 humidity, temperature & pressure sensor
 *
 * @section intro_sec Introduction
 *
 *  Driver for the BME280 humidity, temperature & pressure sensor
 * 
 * These sensors use I2C or SPI to communicate, 2 or 4 pins are required
 * to interface.
 *
 * Designed specifically to work with the Adafruit BME280 Breakout
 * ----> http://www.adafruit.com/products/2650
 *    
 *  Adafruit invests time and resources providing this open source code, 
 *  please support Adafruit and open-source hardware by purchasing 
 *  products from Adafruit!
 *
 * @section author Author
 *
 * Written by Kevin "KTOWN" Townsend for Adafruit Industries.
 *
 * @section license License
 *
 * BSD license, all text here must be included in any redistribution.
 *
 */

#include "Arduino.h"
#include <Wire.h>
#include <SPI.h>
#include "Adafruit_BME280.h"

/**************************************************************************/
/*! 
    @brief  class constructor
*/
/**************************************************************************/
Adafruit_BME280::Adafruit_BME280()
    : _cs(-1), _mosi(-1), _miso(-1), _sck(-1)
{ }

/**************************************************************************/
/*! 
    @brief  class constructor if using hardware SPI
    @param cspin the chip select pin to use
*/
/**************************************************************************/
Adafruit_BME280::Adafruit_BME280(int8_t cspin)
    : _cs(cspin), _mosi(-1), _miso(-1), _sck(-1)
{ }

/**************************************************************************/
/*! 
    @brief  class constructor if using software SPI
    @param cspin the chip select pin to use
    @param mosipin the MOSI pin to use
    @param misopin the MISO pin to use
    @param sckpin the SCK pin to use
*/
/**************************************************************************/
Adafruit_BME280::Adafruit_BME280(int8_t cspin, int8_t mosipin, int8_t misopin, int8_t sckpin)
    : _cs(cspin), _mosi(mosipin), _miso(misopin), _sck(sckpin)
{ }


/**************************************************************************/
/*!
    @brief  Initialise sensor with given parameters / settings
    @param theWire the I2C object to use
    @returns true on success, false otherwise
*/
/**************************************************************************/
bool Adafruit_BME280::begin(TwoWire *theWire)
{
	_wire = theWire;
	_i2caddr = BME280_ADDRESS;
	return init();
}

/**************************************************************************/
/*!
    @brief  Initialise sensor with given parameters / settings
    @param addr the I2C address the device can be found on
    @returns true on success, false otherwise
*/
/**************************************************************************/
bool Adafruit_BME280::begin(uint8_t addr)
{
	_i2caddr = addr;
	_wire = &Wire;
	return init();
}

/**************************************************************************/
/*!
    @brief  Initialise sensor with given parameters / settings
    @param addr the I2C address the device can be found on
    @param theWire the I2C object to use
    @returns true on success, false otherwise
*/
/**************************************************************************/
bool Adafruit_BME280::begin(uint8_t addr, TwoWire *theWire)
{
    _i2caddr = addr;
	_wire = theWire;
	return init();
}

/**************************************************************************/
/*!
    @brief  Initialise sensor with given parameters / settings
    @returns true on success, false otherwise
*/
/**************************************************************************/
bool Adafruit_BME280::begin(void)
{
    _i2caddr = BME280_ADDRESS;
	_wire = &Wire;
	return init();
}

/**************************************************************************/
/*!
    @brief  Initialise sensor with given parameters / settings
    @returns true on success, false otherwise
*/
/**************************************************************************/
bool Adafruit_BME280::init()
{
    // init I2C or SPI sensor interface
    if (_cs == -1) {
        // I2C
        _wire -> begin();
    } else {
        digitalWrite(_cs, HIGH);
        pinMode(_cs, OUTPUT);
        if (_sck == -1) {
            // hardware SPI
            SPI.begin();
        } else {
            // software SPI
            pinMode(_sck, OUTPUT);
            pinMode(_mosi, OUTPUT);
            pinMode(_miso, INPUT);
        }
    }

    // check if sensor, i.e. the chip ID is correct
    if (read8(BME280_REGISTER_CHIPID) != 0x60)
        return false;

    // reset the device using soft-reset
    // this makes sure the IIR is off, etc.
    write8(BME280_REGISTER_SOFTRESET, 0xB6);

    // wait for chip to wake up.
    delay(300);

    // if chip is still reading calibration, delay
    while (isReadingCalibration())
          delay(100);

    readCoefficients(); // read trimming parameters, see DS 4.2.2

    setSampling(); // use defaults

    delay(100);

    return true;
}

/**************************************************************************/
/*!
    @brief  setup sensor with given parameters / settings
    
    This is simply a overload to the normal begin()-function, so SPI users
    don't get confused about the library requiring an address.
    @param mode the power mode to use for the sensor
    @param tempSampling the temp samping rate to use
    @param pressSampling the pressure sampling rate to use
    @param humSampling the humidity sampling rate to use
    @param filter the filter mode to use
    @param duration the standby duration to use
*/
/**************************************************************************/
void Adafruit_BME280::setSampling(sensor_mode       mode,
		 sensor_sampling   tempSampling,
		 sensor_sampling   pressSampling,
		 sensor_sampling   humSampling,
		 sensor_filter     filter,
		 standby_duration  duration) {
    _measReg.mode     = mode;
    _measReg.osrs_t   = tempSampling;
    _measReg.osrs_p   = pressSampling;
        
    
    _humReg.osrs_h    = humSampling;
    _configReg.filter = filter;
    _configReg.t_sb   = duration;

    
    // you must make sure to also set REGISTER_CONTROL after setting the
    // CONTROLHUMID register, otherwise the values won't be applied (see DS 5.4.3)
    write8(BME280_REGISTER_CONTROLHUMID, _humReg.get());
    write8(BME280_REGISTER_CONFIG, _configReg.get());
    write8(BME280_REGISTER_CONTROL, _measReg.get());
}


/**************************************************************************/
/*!
    @brief  Encapsulate hardware and software SPI transfer into one function
    @param x the data byte to transfer
    @returns the data byte read from the device
*/
/**************************************************************************/
uint8_t Adafruit_BME280::spixfer(uint8_t x) {
    // hardware SPI
    if (_sck == -1)
        return SPI.transfer(x);

    // software SPI
    uint8_t reply = 0;
    for (int i=7; i>=0; i--) {
        reply <<= 1;
        digitalWrite(_sck, LOW);
        digitalWrite(_mosi, x & (1<<i));
        digitalWrite(_sck, HIGH);
        if (digitalRead(_miso))
            reply |= 1;
        }
    return reply;
}


/**************************************************************************/
/*!
    @brief  Writes an 8 bit value over I2C or SPI
    @param reg the register address to write to
    @param value the value to write to the register
*/
/**************************************************************************/
void Adafruit_BME280::write8(byte reg, byte value) {
    if (_cs == -1) {
        _wire -> beginTransmission((uint8_t)_i2caddr);
        _wire -> write((uint8_t)reg);
        _wire -> write((uint8_t)value);
        _wire -> endTransmission();
    } else {
        if (_sck == -1)
            SPI.beginTransaction(SPISettings(500000, MSBFIRST, SPI_MODE0));
        digitalWrite(_cs, LOW);
        spixfer(reg & ~0x80); // write, bit 7 low
        spixfer(value);
        digitalWrite(_cs, HIGH);
    if (_sck == -1)
        SPI.endTransaction(); // release the SPI bus
    }
}


/**************************************************************************/
/*!
    @brief  Reads an 8 bit value over I2C or SPI
    @param reg the register address to read from
    @returns the data byte read from the device
*/
/**************************************************************************/
uint8_t Adafruit_BME280::read8(byte reg) {
    uint8_t value;
    
    if (_cs == -1) {
        _wire -> beginTransmission((uint8_t)_i2caddr);
        _wire -> write((uint8_t)reg);
        _wire -> endTransmission();
        _wire -> requestFrom((uint8_t)_i2caddr, (byte)1);
        value = _wire -> read();
    } else {
        if (_sck == -1)
            SPI.beginTransaction(SPISettings(500000, MSBFIRST, SPI_MODE0));
        digitalWrite(_cs, LOW);
        spixfer(reg | 0x80); // read, bit 7 high
        value = spixfer(0);
        digitalWrite(_cs, HIGH);
        if (_sck == -1)
            SPI.endTransaction(); // release the SPI bus
    }
    return value;
}


/**************************************************************************/
/*!
    @brief  Reads a 16 bit value over I2C or SPI
    @param reg the register address to read from
    @returns the 16 bit data value read from the device
*/
/**************************************************************************/
uint16_t Adafruit_BME280::read16(byte reg)
{
    uint16_t value;

    if (_cs == -1) {
        _wire -> beginTransmission((uint8_t)_i2caddr);
        _wire -> write((uint8_t)reg);
        _wire -> endTransmission();
        _wire -> requestFrom((uint8_t)_i2caddr, (byte)2);
        value = (_wire -> read() << 8) | _wire -> read();
    } else {
        if (_sck == -1)
            SPI.beginTransaction(SPISettings(500000, MSBFIRST, SPI_MODE0));
        digitalWrite(_cs, LOW);
        spixfer(reg | 0x80); // read, bit 7 high
        value = (spixfer(0) << 8) | spixfer(0);
        digitalWrite(_cs, HIGH);
        if (_sck == -1)
            SPI.endTransaction(); // release the SPI bus
    }

    return value;
}


/**************************************************************************/
/*!
    @brief  Reads a signed 16 bit little endian value over I2C or SPI
    @param reg the register address to read from
    @returns the 16 bit data value read from the device
*/
/**************************************************************************/
uint16_t Adafruit_BME280::read16_LE(byte reg) {
    uint16_t temp = read16(reg);
    return (temp >> 8) | (temp << 8);
}


/**************************************************************************/
/*!
    @brief  Reads a signed 16 bit value over I2C or SPI
    @param reg the register address to read from
    @returns the 16 bit data value read from the device
*/
/**************************************************************************/
int16_t Adafruit_BME280::readS16(byte reg)
{
    return (int16_t)read16(reg);
}


/**************************************************************************/
/*!
    @brief  Reads a signed little endian 16 bit value over I2C or SPI
    @param reg the register address to read from
    @returns the 16 bit data value read from the device
*/
/**************************************************************************/
int16_t Adafruit_BME280::readS16_LE(byte reg)
{
    return (int16_t)read16_LE(reg);
}


/**************************************************************************/
/*!
    @brief  Reads a 24 bit value over I2C
    @param reg the register address to read from
    @returns the 24 bit data value read from the device
*/
/**************************************************************************/
uint32_t Adafruit_BME280::read24(byte reg)
{
    uint32_t value;

    if (_cs == -1) {
        _wire -> beginTransmission((uint8_t)_i2caddr);
        _wire -> write((uint8_t)reg);
        _wire -> endTransmission();
        _wire -> requestFrom((uint8_t)_i2caddr, (byte)3);

        value = _wire -> read();
        value <<= 8;
        value |= _wire -> read();
        value <<= 8;
        value |= _wire -> read();
    } else {
        if (_sck == -1)
            SPI.beginTransaction(SPISettings(500000, MSBFIRST, SPI_MODE0));
        digitalWrite(_cs, LOW);
        spixfer(reg | 0x80); // read, bit 7 high

        value = spixfer(0);
        value <<= 8;
        value |= spixfer(0);
        value <<= 8;
        value |= spixfer(0);

        digitalWrite(_cs, HIGH);
        if (_sck == -1)
            SPI.endTransaction(); // release the SPI bus
    }

    return value;
}


/**************************************************************************/
/*!
    @brief  Take a new measurement (only possible in forced mode)
*/
/**************************************************************************/
void Adafruit_BME280::takeForcedMeasurement()
{   
    // If we are in forced mode, the BME sensor goes back to sleep after each
    // measurement and we need to set it to forced mode once at this point, so
    // it will take the next measurement and then return to sleep again.
    // In normal mode simply does new measurements periodically.
    if (_measReg.mode == MODE_FORCED) {
        // set to forced mode, i.e. "take next measurement"
        write8(BME280_REGISTER_CONTROL, _measReg.get());
        // wait until measurement has been completed, otherwise we would read
        // the values from the last measurement
        while (read8(BME280_REGISTER_STATUS) & 0x08)
		delay(1);
    }
}


/**************************************************************************/
/*!
    @brief  Reads the factory-set coefficients
*/
/**************************************************************************/
void Adafruit_BME280::readCoefficients(void)
{
    _bme280_calib.dig_T1 = read16_LE(BME280_REGISTER_DIG_T1);
    _bme280_calib.dig_T2 = readS16_LE(BME280_REGISTER_DIG_T2);
    _bme280_calib.dig_T3 = readS16_LE(BME280_REGISTER_DIG_T3);

    _bme280_calib.dig_P1 = read16_LE(BME280_REGISTER_DIG_P1);
    _bme280_calib.dig_P2 = readS16_LE(BME280_REGISTER_DIG_P2);
    _bme280_calib.dig_P3 = readS16_LE(BME280_REGISTER_DIG_P3);
    _bme280_calib.dig_P4 = readS16_LE(BME280_REGISTER_DIG_P4);
    _bme280_calib.dig_P5 = readS16_LE(BME280_REGISTER_DIG_P5);
    _bme280_calib.dig_P6 = readS16_LE(BME280_REGISTER_DIG_P6);
    _bme280_calib.dig_P7 = readS16_LE(BME280_REGISTER_DIG_P7);
    _bme280_calib.dig_P8 = readS16_LE(BME280_REGISTER_DIG_P8);
    _bme280_calib.dig_P9 = readS16_LE(BME280_REGISTER_DIG_P9);

    _bme280_calib.dig_H1 = read8(BME280_REGISTER_DIG_H1);
    _bme280_calib.dig_H2 = readS16_LE(BME280_REGISTER_DIG_H2);
    _bme280_calib.dig_H3 = read8(BME280_REGISTER_DIG_H3);
    _bme280_calib.dig_H4 = (read8(BME280_REGISTER_DIG_H4) << 4) | (read8(BME280_REGISTER_DIG_H4+1) & 0xF);
    _bme280_calib.dig_H5 = (read8(BME280_REGISTER_DIG_H5+1) << 4) | (read8(BME280_REGISTER_DIG_H5) >> 4);
    _bme280_calib.dig_H6 = (int8_t)read8(BME280_REGISTER_DIG_H6);
}

/**************************************************************************/
/*!
    @brief return true if chip is busy reading cal data
    @returns true if reading calibration, false otherwise
*/
/**************************************************************************/
bool Adafruit_BME280::isReadingCalibration(void)
{
  uint8_t const rStatus = read8(BME280_REGISTER_STATUS);

  return (rStatus & (1 << 0)) != 0;
}


/**************************************************************************/
/*!
    @brief  Returns the temperature from the sensor
    @returns the temperature read from the device
*/
/**************************************************************************/
float Adafruit_BME280::readTemperature(void)
{
    int32_t var1, var2;

    int32_t adc_T = read24(BME280_REGISTER_TEMPDATA);
    if (adc_T == 0x800000) // value in case temp measurement was disabled
        return NAN;
    adc_T >>= 4;

    var1 = ((((adc_T>>3) - ((int32_t)_bme280_calib.dig_T1 <<1))) *
            ((int32_t)_bme280_calib.dig_T2)) >> 11;
             
    var2 = (((((adc_T>>4) - ((int32_t)_bme280_calib.dig_T1)) *
              ((adc_T>>4) - ((int32_t)_bme280_calib.dig_T1))) >> 12) *
            ((int32_t)_bme280_calib.dig_T3)) >> 14;

    t_fine = var1 + var2;

    float T = (t_fine * 5 + 128) >> 8;
    return T/100;
}


/**************************************************************************/
/*!
    @brief  Returns the pressure from the sensor
    @returns the pressure value (in Pascal) read from the device
*/
/**************************************************************************/
float Adafruit_BME280::readPressure(void) {
    int64_t var1, var2, p;

    readTemperature(); // must be done first to get t_fine

    int32_t adc_P = read24(BME280_REGISTER_PRESSUREDATA);
    if (adc_P == 0x800000) // value in case pressure measurement was disabled
        return NAN;
    adc_P >>= 4;

    var1 = ((int64_t)t_fine) - 128000;
    var2 = var1 * var1 * (int64_t)_bme280_calib.dig_P6;
    var2 = var2 + ((var1*(int64_t)_bme280_calib.dig_P5)<<17);
    var2 = var2 + (((int64_t)_bme280_calib.dig_P4)<<35);
    var1 = ((var1 * var1 * (int64_t)_bme280_calib.dig_P3)>>8) +
           ((var1 * (int64_t)_bme280_calib.dig_P2)<<12);
    var1 = (((((int64_t)1)<<47)+var1))*((int64_t)_bme280_calib.dig_P1)>>33;

    if (var1 == 0) {
        return 0; // avoid exception caused by division by zero
    }
    p = 1048576 - adc_P;
    p = (((p<<31) - var2)*3125) / var1;
    var1 = (((int64_t)_bme280_calib.dig_P9) * (p>>13) * (p>>13)) >> 25;
    var2 = (((int64_t)_bme280_calib.dig_P8) * p) >> 19;

    p = ((p + var1 + var2) >> 8) + (((int64_t)_bme280_calib.dig_P7)<<4);
    return (float)p/256;
}


/**************************************************************************/
/*!
    @brief  Returns the humidity from the sensor
    @returns the humidity value read from the device
*/
/**************************************************************************/
float Adafruit_BME280::readHumidity(void) {
    readTemperature(); // must be done first to get t_fine

    int32_t adc_H = read16(BME280_REGISTER_HUMIDDATA);
    if (adc_H == 0x8000) // value in case humidity measurement was disabled
        return NAN;
        
    int32_t v_x1_u32r;

    v_x1_u32r = (t_fine - ((int32_t)76800));

    v_x1_u32r = (((((adc_H << 14) - (((int32_t)_bme280_calib.dig_H4) << 20) -
                    (((int32_t)_bme280_calib.dig_H5) * v_x1_u32r)) + ((int32_t)16384)) >> 15) *
                 (((((((v_x1_u32r * ((int32_t)_bme280_calib.dig_H6)) >> 10) *
                      (((v_x1_u32r * ((int32_t)_bme280_calib.dig_H3)) >> 11) + ((int32_t)32768))) >> 10) +
                    ((int32_t)2097152)) * ((int32_t)_bme280_calib.dig_H2) + 8192) >> 14));

    v_x1_u32r = (v_x1_u32r - (((((v_x1_u32r >> 15) * (v_x1_u32r >> 15)) >> 7) *
                               ((int32_t)_bme280_calib.dig_H1)) >> 4));

    v_x1_u32r = (v_x1_u32r < 0) ? 0 : v_x1_u32r;
    v_x1_u32r = (v_x1_u32r > 419430400) ? 419430400 : v_x1_u32r;
    float h = (v_x1_u32r>>12);
    return  h / 1024.0;
}


/**************************************************************************/
/*!
    Calculates the altitude (in meters) from the specified atmospheric
    pressure (in hPa), and sea-level pressure (in hPa).

    @param  seaLevel      Sea-level pressure in hPa
    @returns the altitude value read from the device
*/
/**************************************************************************/
float Adafruit_BME280::readAltitude(float seaLevel)
{
    // Equation taken from BMP180 datasheet (page 16):
    //  http://www.adafruit.com/datasheets/BST-BMP180-DS000-09.pdf

    // Note that using the equation from wikipedia can give bad results
    // at high altitude. See this thread for more information:
    //  http://forums.adafruit.com/viewtopic.php?f=22&t=58064

    float atmospheric = readPressure() / 100.0F;
    return 44330.0 * (1.0 - pow(atmospheric / seaLevel, 0.1903));
}


/**************************************************************************/
/*!
    Calculates the pressure at sea level (in hPa) from the specified altitude 
    (in meters), and atmospheric pressure (in hPa).  
    @param  altitude      Altitude in meters
    @param  atmospheric   Atmospheric pressure in hPa
    @returns the pressure at sea level (in hPa) from the specified altitude
*/
/**************************************************************************/
float Adafruit_BME280::seaLevelForAltitude(float altitude, float atmospheric)
{
    // Equation taken from BMP180 datasheet (page 17):
    //  http://www.adafruit.com/datasheets/BST-BMP180-DS000-09.pdf

    // Note that using the equation from wikipedia can give bad results
    // at high altitude. See this thread for more information:
    //  http://forums.adafruit.com/viewtopic.php?f=22&t=58064

    return atmospheric / pow(1.0 - (altitude/44330.0), 5.255);
}