Andrew's git - arduino-weather.git/blob - libraries/bmp180/bmp180.cpp

   1#include "Arduino.h"
   2#include "bmp180.h"
   3
   4bmp180::bmp180(int pin) {
   5  pinMode(pin, OUTPUT);
   6  _pin = pin;
   7  Wire.begin();
   8  calibrate();
   9}
  10
  11//Calabration of Barometic sensor
  12void bmp180::calibrate() {
  13  _ac1 = readInt(0xAA);
  14  _ac2 = readInt(0xAC);
  15  _ac3 = readInt(0xAE);
  16  _ac4 = readInt(0xB0);
  17  _ac5 = readInt(0xB2);
  18  _ac6 = readInt(0xB4);
  19  _b1 = readInt(0xB6);
  20  _b2 = readInt(0xB8);
  21  _mb = readInt(0xBA);
  22  _mc = readInt(0xBC);
  23  _md = readInt(0xBE);
  24}
  25
  26
  27
  28// Read 1 byte from BMP180
  29char bmp180::read(unsigned char address) {
  30
  31  unsigned char data;
  32
  33  Wire.beginTransmission(bmppin);
  34  Wire.write(address);
  35  Wire.endTransmission();
  36
  37  Wire.requestFrom(bmppin, 1);
  38  while(!Wire.available());
  39
  40  return Wire.read();
  41}
  42
  43// Read 2 bytes from the BMP180. First byte from 'address', second from 'address'+1
  44int bmp180::readInt(unsigned char address) {
  45
  46  unsigned char msb, lsb;
  47
  48  Wire.beginTransmission(bmppin);
  49  Wire.write(address);
  50  Wire.endTransmission();
  51
  52  Wire.requestFrom(bmppin, 2);
  53  while(Wire.available()<2)
  54    ;
  55  msb = Wire.read();
  56  lsb = Wire.read();
  57
  58  return (int) msb<<8 | lsb;
  59}
  60
  61// Read the compensated temperature value
  62unsigned int bmp180::readTemperature(){
  63  unsigned int ut;
  64
  65  // Write 0x2E into Register 0xF4
  66  // This requests a temperature reading
  67  Wire.beginTransmission(bmppin);
  68  Wire.write(0xF4);
  69  Wire.write(0x2E);
  70  Wire.endTransmission();
  71
  72  // Wait at least 4.5ms
  73  delay(5);
  74
  75  // Read two bytes from registers 0xF6 and 0xF7
  76  ut = readInt(0xF6);
  77
  78  long x1, x2;
  79
  80  x1 = (((long)ut - (long)ac6)*(long)ac5) >> 15;
  81  x2 = ((long)mc << 11)/(x1 + md);
  82  b5 = x1 + x2;
  83
  84  float temp = ((b5 + 8)>>4);
  85  temp = temp /10;
  86
  87  return temp;
  88}
  89
  90
  91
  92
  93
  94
  95// Calculate pressure given up (Uncompensated Pressure)
  96// calibration values must be known
  97// b5 is also required so bmp180GetTemperature(...) must be called first.
  98// Value returned will be pressure in units of Pa.
  99
 100// Read the compensated pressure value
 101unsigned long bmp180::readPressure(){
 102
 103  unsigned char msb, lsb, xlsb;
 104  unsigned long up = 0;
 105
 106  // Write 0x34+(OSS<<6) into register 0xF4
 107  // Request a pressure reading w/ oversampling setting
 108  Wire.beginTransmission(bmppin);
 109  Wire.write(0xF4);
 110  Wire.write(0x34 + (OSS<<6));
 111  Wire.endTransmission();
 112
 113  // Wait for conversion, delay time dependent on OSS
 114  delay(2 + (3<<OSS));
 115
 116  // Read register 0xF6 (MSB), 0xF7 (LSB), and 0xF8 (XLSB)
 117  msb = read(0xF6);
 118  lsb = read(0xF7);
 119  xlsb = read(0xF8);
 120
 121  up = (((unsigned long) msb << 16) | ((unsigned long) lsb << 8) | (unsigned long) xlsb) >> (8-OSS); // Calculate uncompensated pressure
 122
 123
 124  long x1, x2, x3, b3, b6, p;
 125  unsigned long b4, b7;
 126
 127  b6 = b5 - 4000;
 128  // Calculate B3
 129  x1 = (b2 * (b6 * b6)>>12)>>11;
 130  x2 = (ac2 * b6)>>11;
 131  x3 = x1 + x2;
 132  b3 = (((((long)ac1)*4 + x3)<<OSS) + 2)>>2;
 133
 134  // Calculate B4
 135  x1 = (ac3 * b6)>>13;
 136  x2 = (b1 * ((b6 * b6)>>12))>>16;
 137  x3 = ((x1 + x2) + 2)>>2;
 138  b4 = (ac4 * (unsigned long)(x3 + 32768))>>15;
 139
 140  b7 = ((unsigned long)(up - b3) * (50000>>OSS));
 141  if (b7 < 0x80000000)
 142    p = (b7<<1)/b4;
 143  else
 144    p = (b7/b4)<<1;
 145
 146  x1 = (p>>8) * (p>>8);
 147  x1 = (x1 * 3038)>>16;
 148  x2 = (-7357 * p)>>16;
 149  p += (x1 + x2 + 3791)>>4;
 150
 151  long pressure = p;
 152  return pressure;
 153}