Spiridion Mbed / BMP180

BMP180 Pressure/Temperature Sensor library

Dependents:   frdm_mikroklimat Weather_Station WMG Sample_BMP180 ... more

Yet another BMP180 library!

Bosch BMP180 is a pressure and temperature sensor which can be addressed through an I2C interface.

This library is based on the Bosch documentation (/media/uploads/spiridion/bst-bmp180-ds000-09.pdf ) and has been tested on LPC1768 and FRM-KL25Z plateforms using the BMP180 Sparkfun breakout (https://www.sparkfun.com/products/11824).

BMP180.cpp@0:9a0671b6009f, 2014-03-08 (annotated)

Committer:
spiridion
Date:
Sat Mar 08 21:42:40 2014 +0000
Revision:
0:9a0671b6009f
Child:
1:072073c79cfd
first release

Who changed what in which revision?

UserRevisionLine numberNew contents of line
spiridion 0:9a0671b6009f 1 /*
spiridion 0:9a0671b6009f 2 @file BMP180.cpp
spiridion 0:9a0671b6009f 3
spiridion 0:9a0671b6009f 4 @brief Barometric Pressure and Temperature Sensor BMP180 Breakout I2C Library
spiridion 0:9a0671b6009f 5
spiridion 0:9a0671b6009f 6 @Author spiridion (http://mailme.spiridion.net)
spiridion 0:9a0671b6009f 7
spiridion 0:9a0671b6009f 8 Tested on LPC1768 and FRDM-KL25Z
spiridion 0:9a0671b6009f 9
spiridion 0:9a0671b6009f 10 Copyright (c) 2014 spiridion
spiridion 0:9a0671b6009f 11 Released under the MIT License (see http://mbed.org/license/mit)
spiridion 0:9a0671b6009f 12
spiridion 0:9a0671b6009f 13 Documentation regarding the BMP180 can be found here:
spiridion 0:9a0671b6009f 14 ...............
spiridion 0:9a0671b6009f 15 */
spiridion 0:9a0671b6009f 16
spiridion 0:9a0671b6009f 17 #include "BMP180.h"
spiridion 0:9a0671b6009f 18 #include "mbed.h"
spiridion 0:9a0671b6009f 19
spiridion 0:9a0671b6009f 20 // Uncomment to test the documentation algorithm against the documentation example
spiridion 0:9a0671b6009f 21 // Result should be 699.64 hPa and 15°C
spiridion 0:9a0671b6009f 22 // #define BMP180_TEST_FORMULA
spiridion 0:9a0671b6009f 23
spiridion 0:9a0671b6009f 24 BMP180::BMP180(PinName sda, PinName scl, int address)
spiridion 0:9a0671b6009f 25 : m_i2c(sda,scl), m_addr(address)
spiridion 0:9a0671b6009f 26 {
spiridion 0:9a0671b6009f 27 Initialize();
spiridion 0:9a0671b6009f 28 }
spiridion 0:9a0671b6009f 29
spiridion 0:9a0671b6009f 30 BMP180::BMP180(I2C& i2c, int address)
spiridion 0:9a0671b6009f 31 : m_i2c(i2c), m_addr(address)
spiridion 0:9a0671b6009f 32 {
spiridion 0:9a0671b6009f 33 Initialize();
spiridion 0:9a0671b6009f 34 }
spiridion 0:9a0671b6009f 35
spiridion 0:9a0671b6009f 36 int BMP180::Initialize(float altitude, int overSamplingSetting)
spiridion 0:9a0671b6009f 37 {
spiridion 0:9a0671b6009f 38 char data[22];
spiridion 0:9a0671b6009f 39 int errors = 0;
spiridion 0:9a0671b6009f 40
spiridion 0:9a0671b6009f 41 m_altitude = altitude;
spiridion 0:9a0671b6009f 42 m_oss = overSamplingSetting;
spiridion 0:9a0671b6009f 43
spiridion 0:9a0671b6009f 44 m_temperature = UNSET_BMP180_TEMPERATURE_VALUE;
spiridion 0:9a0671b6009f 45 m_pressure = UNSET_BMP180_PRESSURE_VALUE;
spiridion 0:9a0671b6009f 46
spiridion 0:9a0671b6009f 47 // read calibration data
spiridion 0:9a0671b6009f 48 data[0]=0xAA;
spiridion 0:9a0671b6009f 49 errors = m_i2c.write(m_addr, data, 1); // set the eeprom pointer position to 0xAA
spiridion 0:9a0671b6009f 50 errors += m_i2c.read(m_addr, data, 22); // read 11 x 16 bits at this position
spiridion 0:9a0671b6009f 51 wait_ms(10);
spiridion 0:9a0671b6009f 52
spiridion 0:9a0671b6009f 53 // store calibration data for further calculus
spiridion 0:9a0671b6009f 54 ac1 = data[0] << 8 | data[1];
spiridion 0:9a0671b6009f 55 ac2 = data[2] << 8 | data[3];
spiridion 0:9a0671b6009f 56 ac3 = data[4] << 8 | data[5];
spiridion 0:9a0671b6009f 57 ac4 = data[6] << 8 | data[7];
spiridion 0:9a0671b6009f 58 ac5 = data[8] << 8 | data[9];
spiridion 0:9a0671b6009f 59 ac6 = data[10] << 8 | data[11];
spiridion 0:9a0671b6009f 60 b1 = data[12] << 8 | data[13];
spiridion 0:9a0671b6009f 61 b2 = data[14] << 8 | data[15];
spiridion 0:9a0671b6009f 62 mb = data[16] << 8 | data[17];
spiridion 0:9a0671b6009f 63 mc = data[18] << 8 | data[19];
spiridion 0:9a0671b6009f 64 md = data[20] << 8 | data[21];
spiridion 0:9a0671b6009f 65
spiridion 0:9a0671b6009f 66 #ifdef BMP180_TEST_FORMULA
spiridion 0:9a0671b6009f 67 ac1 = 408;
spiridion 0:9a0671b6009f 68 ac2 = -72;
spiridion 0:9a0671b6009f 69 ac3 = -14383;
spiridion 0:9a0671b6009f 70 ac4 = 32741;
spiridion 0:9a0671b6009f 71 ac5 = 32757;
spiridion 0:9a0671b6009f 72 ac6 = 23153;
spiridion 0:9a0671b6009f 73 b1 = 6190;
spiridion 0:9a0671b6009f 74 b2 = 4;
spiridion 0:9a0671b6009f 75 mb = -32768;
spiridion 0:9a0671b6009f 76 mc = -8711;
spiridion 0:9a0671b6009f 77 md = 2868;
spiridion 0:9a0671b6009f 78 m_oss = 0;
spiridion 0:9a0671b6009f 79 errors = 0;
spiridion 0:9a0671b6009f 80 #endif // #ifdef BMP180_TEST_FORMULA
spiridion 0:9a0671b6009f 81
spiridion 0:9a0671b6009f 82 return errors? 0 : 1;
spiridion 0:9a0671b6009f 83 }
spiridion 0:9a0671b6009f 84
spiridion 0:9a0671b6009f 85 int BMP180::ReadData(float* pTemperature, float* pPressure)
spiridion 0:9a0671b6009f 86 {
spiridion 0:9a0671b6009f 87 long t, p;
spiridion 0:9a0671b6009f 88
spiridion 0:9a0671b6009f 89 if (!ReadRawTemperature(&t) || !ReadRawPressure(&p))
spiridion 0:9a0671b6009f 90 {
spiridion 0:9a0671b6009f 91 m_temperature = UNSET_BMP180_TEMPERATURE_VALUE;
spiridion 0:9a0671b6009f 92 m_pressure = UNSET_BMP180_PRESSURE_VALUE;
spiridion 0:9a0671b6009f 93 return 0;
spiridion 0:9a0671b6009f 94 }
spiridion 0:9a0671b6009f 95
spiridion 0:9a0671b6009f 96 m_temperature = TrueTemperature(t);
spiridion 0:9a0671b6009f 97 m_pressure = TruePressure(p);
spiridion 0:9a0671b6009f 98
spiridion 0:9a0671b6009f 99 if (pPressure)
spiridion 0:9a0671b6009f 100 *pPressure = m_pressure;
spiridion 0:9a0671b6009f 101 if (pTemperature)
spiridion 0:9a0671b6009f 102 *pTemperature = m_temperature;
spiridion 0:9a0671b6009f 103
spiridion 0:9a0671b6009f 104 return 1;
spiridion 0:9a0671b6009f 105 }
spiridion 0:9a0671b6009f 106
spiridion 0:9a0671b6009f 107 int BMP180::ReadRawTemperature(long* pUt)
spiridion 0:9a0671b6009f 108 {
spiridion 0:9a0671b6009f 109 int errors = 0;
spiridion 0:9a0671b6009f 110 char data[2];
spiridion 0:9a0671b6009f 111
spiridion 0:9a0671b6009f 112 // request temperature measurement
spiridion 0:9a0671b6009f 113 data[0] = 0xF4;
spiridion 0:9a0671b6009f 114 data[1] = 0x2E;
spiridion 0:9a0671b6009f 115 errors = m_i2c.write(m_addr, data, 2); // write 0XF2 into reg 0XF4
spiridion 0:9a0671b6009f 116
spiridion 0:9a0671b6009f 117 wait_ms(4.5F);
spiridion 0:9a0671b6009f 118
spiridion 0:9a0671b6009f 119 // read raw temperature data
spiridion 0:9a0671b6009f 120 data[0] = 0xF6;
spiridion 0:9a0671b6009f 121 errors += m_i2c.write(m_addr, data, 2); // set eeprom pointer position to 0XF6
spiridion 0:9a0671b6009f 122 errors += m_i2c.read(m_addr, data, 2); // get 16 bits at this position
spiridion 0:9a0671b6009f 123
spiridion 0:9a0671b6009f 124 #ifdef BMP180_TEST_FORMULA
spiridion 0:9a0671b6009f 125 errors = 0;
spiridion 0:9a0671b6009f 126 #endif // #ifdef BMP180_TEST_FORMULA
spiridion 0:9a0671b6009f 127
spiridion 0:9a0671b6009f 128 if (errors)
spiridion 0:9a0671b6009f 129 return 0;
spiridion 0:9a0671b6009f 130 else
spiridion 0:9a0671b6009f 131 *pUt = data[0] << 8 | data[1];
spiridion 0:9a0671b6009f 132
spiridion 0:9a0671b6009f 133 #ifdef BMP180_TEST_FORMULA
spiridion 0:9a0671b6009f 134 *pUt = 27898;
spiridion 0:9a0671b6009f 135 #endif // #ifdef BMP180_TEST_FORMULA
spiridion 0:9a0671b6009f 136
spiridion 0:9a0671b6009f 137 return 1;
spiridion 0:9a0671b6009f 138 }
spiridion 0:9a0671b6009f 139
spiridion 0:9a0671b6009f 140 int BMP180::ReadRawPressure(long* pUp)
spiridion 0:9a0671b6009f 141 {
spiridion 0:9a0671b6009f 142 int errors = 0;
spiridion 0:9a0671b6009f 143 char data[2];
spiridion 0:9a0671b6009f 144
spiridion 0:9a0671b6009f 145 // request pressure measurement
spiridion 0:9a0671b6009f 146 data[0] = 0xF4;
spiridion 0:9a0671b6009f 147 data[1] = 0x34 + (m_oss << 6);
spiridion 0:9a0671b6009f 148 errors = m_i2c.write(m_addr, data, 2); // write 0x34 + (m_oss << 6) into reg 0XF4
spiridion 0:9a0671b6009f 149
spiridion 0:9a0671b6009f 150 switch (m_oss)
spiridion 0:9a0671b6009f 151 {
spiridion 0:9a0671b6009f 152 case BMP180_OSS_ULTRA_LOW_POWER: wait_ms(4.5); break;
spiridion 0:9a0671b6009f 153 case BMP180_OSS_NORMAL: wait_ms(7.5); break;
spiridion 0:9a0671b6009f 154 case BMP180_OSS_HIGH_RESOLUTION: wait_ms(13.5); break;
spiridion 0:9a0671b6009f 155 case BMP180_OSS_ULTRA_HIGH_RESOLUTION: wait_ms(25.5); break;
spiridion 0:9a0671b6009f 156 }
spiridion 0:9a0671b6009f 157
spiridion 0:9a0671b6009f 158 // read raw pressure data
spiridion 0:9a0671b6009f 159 data[0] = 0xF6;
spiridion 0:9a0671b6009f 160 errors += m_i2c.write(m_addr, data, 1); // set eeprom pointer position to 0XF6
spiridion 0:9a0671b6009f 161 errors += m_i2c.read(m_addr, data, 2); // get 16 bits at this position
spiridion 0:9a0671b6009f 162
spiridion 0:9a0671b6009f 163 #ifdef BMP180_TEST_FORMULA
spiridion 0:9a0671b6009f 164 errors = 0;
spiridion 0:9a0671b6009f 165 #endif // #ifdef BMP180_TEST_FORMULA
spiridion 0:9a0671b6009f 166
spiridion 0:9a0671b6009f 167 if (errors)
spiridion 0:9a0671b6009f 168 return 0;
spiridion 0:9a0671b6009f 169 else
spiridion 0:9a0671b6009f 170 *pUp = (data[0] << 16 | data[1] << 8) >> (8 - m_oss);
spiridion 0:9a0671b6009f 171 #ifdef BMP180_TEST_FORMULA
spiridion 0:9a0671b6009f 172 *pUp = 23843;
spiridion 0:9a0671b6009f 173 #endif // #ifdef BMP180_TEST_FORMULA
spiridion 0:9a0671b6009f 174
spiridion 0:9a0671b6009f 175 return 1;
spiridion 0:9a0671b6009f 176 }
spiridion 0:9a0671b6009f 177
spiridion 0:9a0671b6009f 178 float BMP180::TrueTemperature(long ut)
spiridion 0:9a0671b6009f 179 {
spiridion 0:9a0671b6009f 180 long t;
spiridion 0:9a0671b6009f 181
spiridion 0:9a0671b6009f 182 // straight out from the documentation
spiridion 0:9a0671b6009f 183 x1 = ((ut - ac6) * ac5) >> 15;
spiridion 0:9a0671b6009f 184 x2 = ((long)mc << 11) / (x1 + md);
spiridion 0:9a0671b6009f 185 b5 = x1 + x2;
spiridion 0:9a0671b6009f 186 t = (b5 + 8) >> 4;
spiridion 0:9a0671b6009f 187
spiridion 0:9a0671b6009f 188 // convert to celcius
spiridion 0:9a0671b6009f 189 return t / 10.F;
spiridion 0:9a0671b6009f 190 }
spiridion 0:9a0671b6009f 191
spiridion 0:9a0671b6009f 192 float BMP180::TruePressure(long up)
spiridion 0:9a0671b6009f 193 {
spiridion 0:9a0671b6009f 194 long p;
spiridion 0:9a0671b6009f 195
spiridion 0:9a0671b6009f 196 // straight out from the documentation
spiridion 0:9a0671b6009f 197 b6 = b5 - 4000;
spiridion 0:9a0671b6009f 198 x1 = (b2 * (b6 * b6 >> 12)) >> 11;
spiridion 0:9a0671b6009f 199 x2 = ac2 * b6 >> 11;
spiridion 0:9a0671b6009f 200 x3 = x1 + x2;
spiridion 0:9a0671b6009f 201 b3 = (((ac1 * 4 + x3) << m_oss) + 2) >> 2;
spiridion 0:9a0671b6009f 202 x1 = (ac3 * b6) >> 13;
spiridion 0:9a0671b6009f 203 x2 = (b1 * ((b6 * b6) >> 12)) >> 16;
spiridion 0:9a0671b6009f 204 x3 = ((x1 + x2) + 2) >> 2;
spiridion 0:9a0671b6009f 205 b4 = ac4 * (unsigned long)(x3 + 32768) >> 15;
spiridion 0:9a0671b6009f 206 b7 = ((unsigned long)up - b3)* (50000 >> m_oss);
spiridion 0:9a0671b6009f 207 if (b7 < 0x80000000)
spiridion 0:9a0671b6009f 208 p = (b7 << 1) / b4;
spiridion 0:9a0671b6009f 209 else
spiridion 0:9a0671b6009f 210 p = (b7 / b4) << 1;
spiridion 0:9a0671b6009f 211 x1 = (p >> 8) * (p >> 8);
spiridion 0:9a0671b6009f 212 x1 = (x1 * 3038) >> 16;
spiridion 0:9a0671b6009f 213 x2 = (-7357 * p) >> 16;
spiridion 0:9a0671b6009f 214 p = p + ((x1 + x2 + 3791) >> 4);
spiridion 0:9a0671b6009f 215
spiridion 0:9a0671b6009f 216 // convert to hPa and, if altitude has been initialized, to sea level pressure
spiridion 0:9a0671b6009f 217 if (m_altitude == 0.F)
spiridion 0:9a0671b6009f 218 return p / 100.F;
spiridion 0:9a0671b6009f 219 else
spiridion 0:9a0671b6009f 220 return p / (100.F * pow((1.F - m_altitude / 44330.0L), 5.255L));
spiridion 0:9a0671b6009f 221 }