/*
    BMP1810 by Bosch
    i2c address 0x77

    oss (oversampling setting) :
    0 = Ultra low power        maximum conversion time: 4.5ms
    1 = Standard               maximum conversion time: 7.5ms
    2 = High resolution        maximum conversion time: 13.5ms
    3 = Ultra high resolution  maximum conversion time: 25.5ms
    * oss is always 0 for temperature measurements
*/

#define BMP180_ADDRESS 0x77     // I2C address of the BMP180

#define AC1    (int16_t)7819     // EEPROM registers 0xAA,0xAB
#define AC2    (int16_t)-997     // EEPROM registers 0xAC,0xAD
#define AC3    (int16_t)-14468   // EEPROM registers 0xAE,0xAF
#define AC4    (uint16_t)33992   // EEPROM registers 0xB0,0xB1
#define AC5    (uint16_t)25359   // EEPROM registers 0xB2,0xB3
#define AC6    (uint16_t)15534   // EEPROM registers 0xB4,0xB5
#define B1     (int16_t)6515     // EEPROM registers 0xB6,0xB7
#define B2     (int16_t)32       // EEPROM registers 0xB8,0xB9
#define MB     (int16_t)-32768   // EEPROM registers 0xBA,0xBB
#define MC     (int16_t)-11786   // EEPROM registers 0xBC,0xBD
#define MD     (int16_t)2601     // EEPROM registers 0xBE,0xBF

#define oss     0                   //Oversampling setting

long temp_raw;
long temp_calc;
float temperature;
long pressure_raw;
long pressure_calc;
float pressure;

void writeI2Cregister(uint8_t address, uint8_t register_number, uint8_t newRegisterState) {
  Wire.beginTransmission(address);
  Wire.write(register_number);
  Wire.write(newRegisterState);
  Wire.endTransmission(true);
}

void BMP180_readEEPROM() {
    // Read factory calibration values from EEPROM
    Wire.beginTransmission(BMP180_ADDRESS);
    Wire.write(0xAA);
    Wire.endTransmission(false);
    Wire.requestFrom(BMP180_ADDRESS, 22, true);
    int16_t AC1 = Wire.read() << 8 | Wire.read();
    int16_t AC2 = Wire.read() << 8 | Wire.read();
    int16_t AC3 = Wire.read() << 8 | Wire.read();
    uint16_t AC4 = Wire.read() << 8 | Wire.read();
    uint16_t AC5 = Wire.read() << 8 | Wire.read();
    uint16_t AC6 = Wire.read() << 8 | Wire.read();
    int16_t B1 = Wire.read() << 8 | Wire.read();
    int16_t B2 = Wire.read() << 8 | Wire.read();
    int16_t MB = Wire.read() << 8 | Wire.read();
    int16_t MC = Wire.read() << 8 | Wire.read();
    int16_t MD = Wire.read() << 8 | Wire.read();
}
long BMP180_read() {
    // Start new temperature measurement
    writeI2Cregister(BMP180_ADDRESS, 0xF4, 0 << 6 | 1 << 5 | 0b01110);
    delay(5); // Max conversion time is 4.5ms
    // Read temperature
    Wire.beginTransmission(BMP180_ADDRESS);
    Wire.write(0xF6);
    Wire.endTransmission(false);
    Wire.requestFrom(BMP180_ADDRESS, 2, true);
    temp_raw = Wire.read() << 8 | Wire.read();

    // Start new pressure measurement
    writeI2Cregister(BMP180_ADDRESS, 0xF4, oss << 6 | 1 << 5 | 0b10100);
    delay(5); // Max conversion time is 4.5ms (oss = 0)
    // Read pressure
    Wire.beginTransmission(BMP180_ADDRESS);
    Wire.write(0xF6);
    Wire.endTransmission(false);
    Wire.requestFrom(BMP180_ADDRESS, 3, true);
    long msb = Wire.read();
    long lsb = Wire.read();
    long xlsb = Wire.read();
    pressure_raw = (msb << 16 | lsb << 8 | xlsb) >> (8 - oss);
}

void BMP180_convert() {
  long X1;
  long X2;
  long X3;
  long B3;
  unsigned long B4;
  long B5;
  long B6;
  unsigned long B7;

  // Convert temperature
  X1 = (temp_raw - AC6) * AC5 / 32768;
  X2 = MC * (long)2048 / (X1 + MD);
  B5 = X1 + X2;
  temp_calc = (B5 + 8) / 16;
  temperature = temp_calc / 10.0;

  // Convert pressure
  B6 = B5 - 4000;
  X1 = (B2 * (B6 * B6 / 4096)) / 2048;
  X2 = AC2 * B6 / 2048;
  X3 = X1 + X2;
  B3 = ((((long)AC1 * 4 + X3) << oss) + 2) / 4;
  X1 = AC3 * B6 / 8192;
  X2 = (B1 * (B6 * B6 / 4096)) / 65536;
  X3 = ((X1 + X2) + 2) / 4;
  B4 = AC4 * (unsigned long)(X3 + 32768) / 32768;
  B7 = ((unsigned long)pressure_raw - B3) * (50000 >> oss);
  if (B7 < 0x80000000) {
    pressure_calc = (B7 * 2) / B4;
  }
  else {
    pressure_calc = (B7 / B4) * 2;
  }
  X1 = (pressure_calc / 256) * (pressure_calc / 256);
  X1 = (X1 * 3038) / 65536;
  X2 = (-7357 * pressure_calc) / 65536;
  pressure_calc = pressure_calc + (X1 + X2 + 3791) / 16;
  pressure = pressure_calc / 100.0f;
}