BMP085.cpp

00001 /*
00002  * BMP085.cpp
00003  *
00004  *  Created on: 13 juil. 2013
00005  *      Author: Vincent
00006  */
00007 
00008 #include "BMP085.h"
00009 #include <new>
00010 
00011 BMP085::BMP085(PinName sda, PinName scl) : i2c_(*reinterpret_cast<I2C*>(i2cRaw))
00012 {
00013     // Placement new to avoid additional heap memory allocation.
00014     new(i2cRaw) I2C(sda, scl);
00015     i2c_.frequency(50000);
00016     pressure = 101300;
00017     temperature = 298;
00018 }
00019 
00020 BMP085::~BMP085()
00021 {
00022     // If the I2C object is initialized in the buffer in this object, call destructor of it.
00023     if(&i2c_ == reinterpret_cast<I2C*>(&i2cRaw))
00024         reinterpret_cast<I2C*>(&i2cRaw)->~I2C();
00025 }
00026 
00027 // oversampling setting
00028 // 0 = ultra low power
00029 // 1 = standard
00030 // 2 = high
00031 // 3 = ultra high resolution
00032 const unsigned char oversampling_setting = 3; //oversampling for measurement
00033 const unsigned char pressure_conversiontime[4] = {4.5, 7.5, 13.5, 25.5 };  // delays for oversampling settings 0, 1, 2 and 3
00034 
00035 // sensor registers from the BOSCH BMP085 datasheet
00036 short ac1;
00037 short ac2;
00038 short ac3;
00039 unsigned short ac4;
00040 unsigned short ac5;
00041 unsigned short ac6;
00042 short b1;
00043 short b2;
00044 short mb;
00045 short mc;
00046 short md;
00047 
00048 void BMP085::writeRegister(unsigned char r, unsigned char v)
00049 {
00050   char cmd1[2];
00051   cmd1[0] = r;
00052   cmd1[1] = v;
00053   i2c_.write(I2C_ADDRESS,cmd1, 2);
00054 }
00055 
00056 // read a 16 bit register
00057 int BMP085::readIntRegister(unsigned char r)
00058 {
00059   char cmd1[2];
00060   char cmd2[1];
00061   //unsigned char msb, lsb;
00062   cmd2[0] = r;
00063   i2c_.write(I2C_ADDRESS,cmd2, 1);
00064   i2c_.read(I2C_ADDRESS, cmd1, 2);
00065   return (((int)cmd1[0]<<8) | ((int)cmd1[1]));
00066 }
00067 
00068 // read uncompensated temperature value
00069 unsigned int BMP085::readUT() {
00070   writeRegister(0xf4,0x2e);
00071   wait(0.0045); // the datasheet suggests 4.5 ms
00072   return readIntRegister(0xf6);
00073 
00074 }
00075 
00076 // read uncompensated pressure value
00077 long BMP085::readUP() {
00078   writeRegister(0xf4,0x34+(oversampling_setting<<6));
00079   wait(pressure_conversiontime[oversampling_setting]*0.001);
00080 
00081   //unsigned char msb, lsb, xlsb;
00082   char cmd1[3];
00083   char cmd0[1];
00084   cmd0[0] = 0xf6;
00085   i2c_.write(I2C_ADDRESS,cmd0, 1);
00086   i2c_.read(I2C_ADDRESS, cmd1, 3);
00087   return (((long)cmd1[0]<<16) | ((long)cmd1[1]<<8) | ((long)cmd1[2])) >>(8-oversampling_setting);
00088 
00089 }
00090 
00091 // Below there are the utility functions to get data from the sensor.
00092 
00093 // read temperature and pressure from sensor
00094 void BMP085::readSensor() {
00095 
00096   long ut= readUT();
00097   long up = readUP();
00098 
00099 
00100   int x1, x2, x3, b3, b5, b6, p;
00101   unsigned int b4, b7;
00102   //calculate true temperature
00103   x1 = ((long)ut - ac6) * ac5 >> 15;
00104   x2 = ((long) mc << 11) / (x1 + md);
00105   b5 = x1 + x2;
00106   temperature = (b5 + 8) >> 4;
00107 
00108   //calculate true pressure
00109   b6 = b5 - 4000;
00110   x1 = (b2 * (b6 * b6 >> 12)) >> 11;
00111   x2 = ac2 * b6 >> 11;
00112   x3 = x1 + x2;
00113 
00114   if (oversampling_setting == 3) b3 = ((int32_t) ac1 * 4 + x3 + 2) << 1;
00115   if (oversampling_setting == 2) b3 = ((int32_t) ac1 * 4 + x3 + 2);
00116   if (oversampling_setting == 1) b3 = ((int32_t) ac1 * 4 + x3 + 2) >> 1;
00117   if (oversampling_setting == 0) b3 = ((int32_t) ac1 * 4 + x3 + 2) >> 2;
00118 
00119   x1 = ac3 * b6 >> 13;
00120   x2 = (b1 * (b6 * b6 >> 12)) >> 16;
00121   x3 = ((x1 + x2) + 2) >> 2;
00122   b4 = (ac4 * (unsigned long) (x3 + 32768)) >> 15;
00123   b7 = ((unsigned long) up - b3) * (50000 >> oversampling_setting);
00124   p = b7 < 0x80000000 ? (b7 * 2) / b4 : (b7 / b4) * 2;
00125 
00126   x1 = (p >> 8) * (p >> 8);
00127   x1 = (x1 * 3038) >> 16;
00128   x2 = (-7357 * p) >> 16;
00129   pressure = p + ((x1 + x2 + 3791) >> 4);
00130 }
00131 
00132 void  BMP085::getCalibrationData() {
00133   ac1 = readIntRegister(0xAA);
00134   ac2 = readIntRegister(0xAC);
00135   ac3 = readIntRegister(0xAE);
00136   ac4 = readIntRegister(0xB0);
00137   ac5 = readIntRegister(0xB2);
00138   ac6 = readIntRegister(0xB4);
00139   b1 = readIntRegister(0xB6);
00140   b2 = readIntRegister(0xB8);
00141   mb = readIntRegister(0xBA);
00142   mc = readIntRegister(0xBC);
00143   md = readIntRegister(0xBE);
00144 }
00145 
00146 float BMP085::press(void)
00147 {
00148     return(pressure);
00149 }
00150 
00151 float BMP085::temp(void)
00152 {
00153     return(temperature);
00154 }
00155 
00156 float BMP085::altitud(void)
00157 {
00158     //press();
00159    // temp();
00160     float To=298;
00161     float ho=0;
00162     float Po=101325;
00163     //ecuacion
00164     float c=(To-0.0065*ho);
00165     float e=(pressure/Po);
00166     float d=exp(0.19082*log(e));
00167     float b=c*d;
00168     float alt=153.84615*(To-b);
00169     return(alt);
00170 }
00171