Adafruit_BMP085.cpp

/*************************************************** 
  This is a library for the BMP085 Barometric Pressure & Temp Sensor

  Designed specifically to work with the Adafruit BMP085 Breakout 
  ----> https://www.adafruit.com/products/391

  These displays use I2C to communicate, 2 pins are required to  
  interface
  Adafruit invests time and resources providing this open source code, 
  please support Adafruit and open-source hardware by purchasing 
  products from Adafruit!

  Written by Limor Fried/Ladyada for Adafruit Industries.  
  BSD license, all text above must be included in any redistribution
 
  -~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~
  modified to work with the TinyWire Master library (TinyWireM)
  by johngineer 10-31-2011 -- boo!

  NOTE: to make use of the debug code herein you MUST include the
  ATTiny serial library in your main program.	

****************************************************/

#include "tinyBMP085.h"
#include <util/delay.h>

BMP085::BMP085() {
}


void BMP085::begin(uint8_t mode) {
  if (mode > BMP085_ULTRAHIGHRES) 
    mode = BMP085_ULTRAHIGHRES;
  oversampling = mode;

  TinyWireM.begin();

  /* read calibration data */
  ac1 = read16(BMP085_CAL_AC1);
  ac2 = read16(BMP085_CAL_AC2);
  ac3 = read16(BMP085_CAL_AC3);
  ac4 = read16(BMP085_CAL_AC4);
  ac5 = read16(BMP085_CAL_AC5);
  ac6 = read16(BMP085_CAL_AC6);

  b1 = read16(BMP085_CAL_B1);
  b2 = read16(BMP085_CAL_B2);

  mb = read16(BMP085_CAL_MB);
  mc = read16(BMP085_CAL_MC);
  md = read16(BMP085_CAL_MD);

#if (BMP085_DEBUG == 1)
  Serial.print("ac1 = "); Serial.println(ac1, DEC);
  Serial.print("ac2 = "); Serial.println(ac2, DEC);
  Serial.print("ac3 = "); Serial.println(ac3, DEC);
  Serial.print("ac4 = "); Serial.println(ac4, DEC);
  Serial.print("ac5 = "); Serial.println(ac5, DEC);
  Serial.print("ac6 = "); Serial.println(ac6, DEC);

  Serial.print("b1 = "); Serial.println(b1, DEC);
  Serial.print("b2 = "); Serial.println(b2, DEC);

  Serial.print("mb = "); Serial.println(mb, DEC);
  Serial.print("mc = "); Serial.println(mc, DEC);
  Serial.print("md = "); Serial.println(md, DEC);
#endif
}

uint16_t BMP085::readRawTemperature(void) {
  write8(BMP085_CONTROL, BMP085_READTEMPCMD);
  _delay_ms(5);
#if BMP085_DEBUG == 1
  Serial.print("Raw temp: "); Serial.println(read16(BMP085_TEMPDATA));
#endif
  return read16(BMP085_TEMPDATA);
}

uint32_t BMP085::readRawPressure(void) {
  uint32_t raw;

  write8(BMP085_CONTROL, BMP085_READPRESSURECMD + (oversampling << 6));

  if (oversampling == BMP085_ULTRALOWPOWER) 
    _delay_ms(5);
  else if (oversampling == BMP085_STANDARD) 
    _delay_ms(8);
  else if (oversampling == BMP085_HIGHRES) 
    _delay_ms(14);
  else 
    _delay_ms(26);

  raw = read16(BMP085_PRESSUREDATA);
  raw <<= 8;
  raw |= read8(BMP085_PRESSUREDATA+2);
  raw >>= (8 - oversampling);
#if BMP085_DEBUG == 1
  Serial.print("Raw pressure: "); Serial.println(raw);
#endif
  return raw;
}


int32_t BMP085::readPressure(void) {
  int32_t UT, UP, B3, B5, B6, X1, X2, X3, p;
  uint32_t B4, B7;

  UT = readRawTemperature();
  UP = readRawPressure();

#if BMP085_DEBUG == 1
  // use datasheet numbers!
  UT = 27898;
  UP = 23843;
  ac6 = 23153;
  ac5 = 32757;
  mc = -8711;
  md = 2868;
  b1 = 6190;
  b2 = 4;
  ac3 = -14383;
  ac2 = -72;
  ac1 = 408;
  ac4 = 32741;
  oversampling = 0;
#endif

  // do temperature calculations
  X1 = ((UT - (int32_t)ac6) * (int32_t)ac5) >> 15;
  X2 = ((int32_t)mc << 11) - (X1 + md)/2;     // round up
  X2 /= (X1 + md);
  B5 = X1 + X2;

#if BMP085_DEBUG == 1
  Serial.print("X1 = "); Serial.println(X1);
  Serial.print("X2 = "); Serial.println(X2);
  Serial.print("B5 = "); Serial.println(B5);
#endif

  // do pressure calcs
  B6 = B5 - 4000;
  X1 = ((int32_t)b2 * ( (B6 * B6)>>12 )) >> 11;
  X2 = ((int32_t)ac2 * B6) >> 11;
  X3 = X1 + X2;
  B3 = ((((int32_t)ac1*4 + X3) << oversampling) + 2) / 4;

#if BMP085_DEBUG == 1
  Serial.print("B6 = "); Serial.println(B6);
  Serial.print("X1 = "); Serial.println(X1);
  Serial.print("X2 = "); Serial.println(X2);
  Serial.print("B3 = "); Serial.println(B3);
#endif

  X1 = ((int32_t)ac3 * B6) >> 13;
  X2 = ((int32_t)b1 * ((B6 * B6) >> 12)) >> 16;
  X3 = ((X1 + X2) + 2) >> 2;
  B4 = ((uint32_t)ac4 * (uint32_t)(X3 + 32768)) >> 15;
  B7 = ((uint32_t)UP - B3) * (uint32_t)( 50000UL >> oversampling );

#if BMP085_DEBUG == 1
  Serial.print("X1 = "); Serial.println(X1);
  Serial.print("X2 = "); Serial.println(X2);
  Serial.print("B4 = "); Serial.println(B4);
  Serial.print("B7 = "); Serial.println(B7);
#endif

  if (B7 < 0x80000000) {
    p = (B7 * 2) / B4;
  } else {
    p = (B7 * 2) / B3;
  }
  X1 = (p >> 8) * (p >> 8);
  X1 = (X1 * 3038) >> 16;
  X2 = (-7357 * p) >> 16;

#if BMP085_DEBUG == 1
  Serial.print("p = "); Serial.println(p);
  Serial.print("X1 = "); Serial.println(X1);
  Serial.print("X2 = "); Serial.println(X2);
#endif

  p = p + ((X1 + X2 + (int32_t)3791)>>4);
#if BMP085_DEBUG == 1
  Serial.print("p = "); Serial.println(p);
#endif
  return p;
}


//float BMP085::readTemperature(void) {
int32_t BMP085::readTemperature(void) {

  int32_t UT, X1, X2, B5;     // following ds convention
  //float temp;
  int32_t temp;

  UT = readRawTemperature();

#if BMP085_DEBUG == 1
  // use datasheet numbers!
  UT = 27898;
  ac6 = 23153;
  ac5 = 32757;
  mc = -8711;
  md = 2868;
#endif

  // step 1
  X1 = ((UT - (int32_t)ac6) * (int32_t)ac5) >> 15;
  X2 = ((int32_t)mc << 11) / (X1 + (int32_t)md);
  B5 = X1 + X2;
  temp = (B5 + 8) >> 4;
  //temp /= 10;

  //return (int32_t)temp;
  return temp;
}


/************************************************************************
   Uncomment the function below to make use of the readAltitude function.
   This function invokes the math.h library for the "pow()" function, and
   as such takes up considerable program space. If you don't need to
   calculate altitude, leave it out!
*************************************************************************/

/*
float BMP085::readAltitude(float sealevelPressure) {
  float altitude;

  float pressure = readPressure();

  altitude = 44330 * (1.0 - pow(pressure /sealevelPressure,0.1903));

  return altitude;
}
*/


uint8_t BMP085::read8(uint8_t a) {
  uint8_t ret;

  TinyWireM.beginTransmission(BMP085_I2CADDR); // start transmission to device 
  TinyWireM.send(a); // sends register address to read from
  TinyWireM.endTransmission(); // end transmission
  
  TinyWireM.beginTransmission(BMP085_I2CADDR); // start transmission to device 
  TinyWireM.requestFrom(BMP085_I2CADDR, 1);// send data n-bytes read
  ret = TinyWireM.receive(); // receive DATA
  //TinyWireM.endTransmission(); // end transmission 

  return ret;
}

uint16_t BMP085::read16(uint8_t a) {
  uint16_t ret;

  TinyWireM.beginTransmission(BMP085_I2CADDR); // start transmission to device 
  TinyWireM.send(a); // sends register address to read from
  TinyWireM.endTransmission(); // end transmission
  
  TinyWireM.beginTransmission(BMP085_I2CADDR); // start transmission to device 
  TinyWireM.requestFrom(BMP085_I2CADDR, 2);// send data n-bytes read
  ret = TinyWireM.receive(); // receive DATA
  ret <<= 8;
  ret |= TinyWireM.receive(); // receive DATA
  //TinyWireM.endTransmission(); // end transmission


  return ret;
}

void BMP085::write8(uint8_t a, uint8_t d) {
  TinyWireM.beginTransmission(BMP085_I2CADDR); // start transmission to device 
  TinyWireM.send(a); // sends register address to read from
  TinyWireM.send(d);  // write data
  TinyWireM.endTransmission(); // end transmission


}