Seeed_BMP280.cpp

#include "Seeed_BMP280.h"

// #define BMP280_DEBUG_PRINT

bool BMP280::init(int i2c_addr) {
  uint8_t chip_id = 0;
  uint8_t retry = 0;
  _devAddr = i2c_addr;
  Wire.begin();
  while ((retry++ < 5) && (chip_id != 0x58)) {
    chip_id = bmp280Read8(BMP280_REG_CHIPID);
#ifdef BMP280_DEBUG_PRINT
    Serial.print("Read chip ID: ");
    Serial.println(chip_id);
#endif
    delay(100);
  }
  dig_T1 = bmp280Read16LE(BMP280_REG_DIG_T1);
  dig_T2 = bmp280ReadS16LE(BMP280_REG_DIG_T2);
  dig_T3 = bmp280ReadS16LE(BMP280_REG_DIG_T3);
  dig_P1 = bmp280Read16LE(BMP280_REG_DIG_P1);
  dig_P2 = bmp280ReadS16LE(BMP280_REG_DIG_P2);
  dig_P3 = bmp280ReadS16LE(BMP280_REG_DIG_P3);
  dig_P4 = bmp280ReadS16LE(BMP280_REG_DIG_P4);
  dig_P5 = bmp280ReadS16LE(BMP280_REG_DIG_P5);
  dig_P6 = bmp280ReadS16LE(BMP280_REG_DIG_P6);
  dig_P7 = bmp280ReadS16LE(BMP280_REG_DIG_P7);
  dig_P8 = bmp280ReadS16LE(BMP280_REG_DIG_P8);
  dig_P9 = bmp280ReadS16LE(BMP280_REG_DIG_P9);
  writeRegister(BMP280_REG_CONTROL, 0x3F);
  return true;
}

float BMP280::getTemperature(void) {
  int32_t var1, var2;
  int32_t adc_T = bmp280Read24(BMP280_REG_TEMPDATA);
  // Check if the last transport successed
  if (!isTransport_OK) {
    return 0;
  }
  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 BMP280::getPressure(void) {
  int64_t var1, var2, p;
  // Call getTemperature to get t_fine
  getTemperature();
  // Check if the last transport successed
  if (!isTransport_OK) {
    return 0;
  }
  int32_t adc_P = bmp280Read24(BMP280_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;
}

float BMP280::calcAltitude(float p0, float p1, float t) {
  float C;
  C = (p0 / p1);
  C = pow(C, (1 / 5.25588)) - 1.0;
  C = (C * (t + 273.15)) / 0.0065;
  return C;
}

float BMP280::calcAltitude(float p0) {
  if (!isTransport_OK) {
    return 0;
  }
  float t = getTemperature();
  float p1 = getPressure();
  return calcAltitude(p0, p1, t);
}

uint8_t BMP280::bmp280Read8(uint8_t reg) {
  Wire.beginTransmission(_devAddr);
  Wire.write(reg);
  Wire.endTransmission();
  Wire.requestFrom(_devAddr, 1);
  // return 0 if slave didn't response
  if (Wire.available() < 1) {
    isTransport_OK = false;
    return 0;
  } else if (isTransport_OK == false) {
    isTransport_OK = true;
  }
  return Wire.read();
}

uint16_t BMP280::bmp280Read16(uint8_t reg) {
  uint8_t msb, lsb;
  Wire.beginTransmission(_devAddr);
  Wire.write(reg);
  Wire.endTransmission();
  Wire.requestFrom(_devAddr, 2);
  // return 0 if slave didn't response
  if (Wire.available() < 2) {
    isTransport_OK = false;
    return 0;
  } else {
    isTransport_OK = true;
  }
  msb = Wire.read();
  lsb = Wire.read();
  return (uint16_t) msb << 8 | lsb;
}

uint16_t BMP280::bmp280Read16LE(uint8_t reg) {
  uint16_t data = bmp280Read16(reg);
  return (data >> 8) | (data << 8);
}

int16_t BMP280::bmp280ReadS16(uint8_t reg) {
  return (int16_t)bmp280Read16(reg);
}

int16_t BMP280::bmp280ReadS16LE(uint8_t reg) {
  return (int16_t)bmp280Read16LE(reg);
}

uint32_t BMP280::bmp280Read24(uint8_t reg) {
  uint32_t data;
  Wire.beginTransmission(_devAddr);
  Wire.write(reg);
  Wire.endTransmission();
  Wire.requestFrom(_devAddr, 3);
  // return 0 if slave didn't response
  if (Wire.available() < 3) {
    isTransport_OK = false;
    return 0;
  } else if (isTransport_OK == false) {
    isTransport_OK = true;
    if (!init(_devAddr)) {
#ifdef BMP280_DEBUG_PRINT
      Serial.println("Device not connected or broken!");
#endif
    }
  }
  data = Wire.read();
  data <<= 8;
  data |= Wire.read();
  data <<= 8;
  data |= Wire.read();
  return data;
}

void BMP280::writeRegister(uint8_t reg, uint8_t val) {
  Wire.beginTransmission(_devAddr); // start transmission to device
  Wire.write(reg); // send register address
  Wire.write(val); // send value to write
  Wire.endTransmission(); // end transmission
}