BME280.cpp

#include "BME280.h"

bool BME280::init(void)
{
  Wire.begin();

  if(BME280Read8(BME280_REG_CHIPID) != 0x60)
    return false;

  dig_T1 = BME280Read16LE(BME280_REG_DIG_T1);
  dig_T2 = BME280ReadS16LE(BME280_REG_DIG_T2);
  dig_T3 = BME280ReadS16LE(BME280_REG_DIG_T3);

  dig_P1 = BME280Read16LE(BME280_REG_DIG_P1);
  dig_P2 = BME280ReadS16LE(BME280_REG_DIG_P2);
  dig_P3 = BME280ReadS16LE(BME280_REG_DIG_P3);
  dig_P4 = BME280ReadS16LE(BME280_REG_DIG_P4);
  dig_P5 = BME280ReadS16LE(BME280_REG_DIG_P5);
  dig_P6 = BME280ReadS16LE(BME280_REG_DIG_P6);
  dig_P7 = BME280ReadS16LE(BME280_REG_DIG_P7);
  dig_P8 = BME280ReadS16LE(BME280_REG_DIG_P8);
  dig_P9 = BME280ReadS16LE(BME280_REG_DIG_P9);

  dig_H1 = BME280Read8(BME280_REG_DIG_H1);
  dig_H2 = BME280Read16LE(BME280_REG_DIG_H2);
  dig_H3 = BME280Read8(BME280_REG_DIG_H3);
  dig_H4 = (BME280Read8(BME280_REG_DIG_H4) << 4) | (0x0F & BME280Read8(BME280_REG_DIG_H4 + 1));
  dig_H5 = (BME280Read8(BME280_REG_DIG_H5 + 1) << 4) | (0x0F & BME280Read8(BME280_REG_DIG_H5) >> 4);
  dig_H6 = (int8_t)BME280Read8(BME280_REG_DIG_H6);

  writeRegister(BME280_REG_CONTROLHUMID, 0x05);  //Choose 16X oversampling
  writeRegister(BME280_REG_CONTROL, 0xB7);  //Choose 16X oversampling

  return true;
}

float BME280::getTemperature(void)
{
  int32_t var1, var2;

  int32_t adc_T = BME280Read24(BME280_REG_TEMPDATA);
  adc_T >>= 4;
  var1 = (((adc_T >> 3) - ((int32_t)(dig_T1 << 1))) *
    ((int32_t)dig_T2)) >> 11;

  var2 = (((((adc_T >> 4) - ((int32_t)dig_T1)) *
    ((adc_T >> 4) - ((int32_t)dig_T1))) >> 12) *
    ((int32_t)dig_T3)) >> 14;

  t_fine = var1 + var2;
  float T = (t_fine * 5 + 128) >> 8;
  return T/100;
}

uint32_t BME280::getPressure(void)
{
  int64_t var1, var2, p;

  // Call getTemperature to get t_fine
  getTemperature();

  int32_t adc_P = BME280Read24(BME280_REG_PRESSUREDATA);
  adc_P >>= 4;

  var1 = ((int64_t)t_fine) - 128000;
  var2 = var1 * var1 * (int64_t)dig_P6;
  var2 = var2 + ((var1*(int64_t)dig_P5)<<17);
  var2 = var2 + (((int64_t)dig_P4)<<35);
  var1 = ((var1 * var1 * (int64_t)dig_P3)>>8) + ((var1 * (int64_t)dig_P2)<<12);
  var1 = (((((int64_t)1)<<47)+var1))*((int64_t)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)dig_P9) * (p>>13) * (p>>13)) >> 25;
  var2 = (((int64_t)dig_P8) * p) >> 19;
  p = ((p + var1 + var2) >> 8) + (((int64_t)dig_P7)<<4);
  return (uint32_t)p/256;
}

uint32_t BME280::getHumidity(void)
{
  int32_t v_x1_u32r, adc_H;

  // Call getTemperature to get t_fine
  getTemperature();

  adc_H = BME280Read16(BME280_REG_HUMIDITYDATA);

  v_x1_u32r = (t_fine - ((int32_t)76800));
  v_x1_u32r = (((((adc_H << 14) - (((int32_t)dig_H4) << 20) - (((int32_t)dig_H5) * v_x1_u32r)) + ((int32_t)16384)) >> 15) * (((((((v_x1_u32r * ((int32_t)dig_H6)) >> 10) * (((v_x1_u32r * ((int32_t)dig_H3)) >> 11) + ((int32_t)32768))) >> 10) + ((int32_t)2097152)) * ((int32_t)dig_H2) + 8192) >> 14));
  v_x1_u32r = (v_x1_u32r - (((((v_x1_u32r >> 15) * (v_x1_u32r >> 15)) >> 7) * ((int32_t)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);
  return (uint32_t)(v_x1_u32r>>12)/1024.0;
}

float BME280::calcAltitude(float pressure)
{
  float A = pressure/101325;
  float B = 1/5.25588;
  float C = pow(A,B);
  C = 1.0 - C;
  C = C /0.0000225577;
  return C;
}

uint8_t BME280::BME280Read8(uint8_t reg)
{
  Wire.beginTransmission(BME280_ADDRESS);
  Wire.write(reg);
  Wire.endTransmission();

  Wire.requestFrom(BME280_ADDRESS, 1);
  while(!Wire.available());
  return Wire.read();
}

uint16_t BME280::BME280Read16(uint8_t reg)
{
  uint8_t msb, lsb;

  Wire.beginTransmission(BME280_ADDRESS);
  Wire.write(reg);
  Wire.endTransmission();

  Wire.requestFrom(BME280_ADDRESS, 2);
  while(Wire.available()<2);
  msb = Wire.read();
  lsb = Wire.read();

  return (uint16_t) msb<<8 | lsb;
}

uint16_t BME280::BME280Read16LE(uint8_t reg)
{
  uint16_t data = BME280Read16(reg);
  return (data >> 8) | (data << 8);
}

int16_t BME280::BME280ReadS16(uint8_t reg)
{
  return (int16_t)BME280Read16(reg);
}

int16_t BME280::BME280ReadS16LE(uint8_t reg)
{
  return (int16_t)BME280Read16LE(reg);
}

uint32_t BME280::BME280Read24(uint8_t reg)
{
  uint32_t data;

  Wire.beginTransmission(BME280_ADDRESS);
  Wire.write(reg);
  Wire.endTransmission();

  Wire.requestFrom(BME280_ADDRESS, 3);
  while(Wire.available()<3);
  data = Wire.read();
  data <<= 8;
  data |= Wire.read();
  data <<= 8;
  data |= Wire.read();

  return data;
}

void BME280::writeRegister(uint8_t reg, uint8_t val)
{
  Wire.beginTransmission(BME280_ADDRESS); // start transmission to device
  Wire.write(reg);       // send register address
  Wire.write(val);         // send value to write
  Wire.endTransmission();     // end transmission
}