Omar Hagrass / bmp085_lib1

Pressure Sensor

Dependencies:   mbed-src

Fork of bmp085_lib by Suga koubou

BMP085/BMP085.cpp@2:4fe211aae36e, 2015-08-11 (annotated)

Committer:
Hagrass
Date:
Tue Aug 11 14:01:49 2015 +0000
Revision:
2:4fe211aae36e
Parent:
1:1d88eb9f5bbd 
PressureSensor

Who changed what in which revision?

UserRevisionLine numberNew contents of line
okini3939 0:dbba605ca87c 1 /*
okini3939 0:dbba605ca87c 2 * mbed library to use a Bosch Sensortec BMP085 sensor
okini3939 0:dbba605ca87c 3 * Copyright (c) 2010 Hiroshi Suga
okini3939 0:dbba605ca87c 4 * Released under the MIT License: http://mbed.org/license/mit
okini3939 0:dbba605ca87c 5 */
okini3939 0:dbba605ca87c 6
okini3939 0:dbba605ca87c 7 #include "mbed.h"
okini3939 0:dbba605ca87c 8 #include "BMP085.h"
okini3939 0:dbba605ca87c 9
okini3939 0:dbba605ca87c 10 #define WEATHER_BMP085 0xee
okini3939 0:dbba605ca87c 11 #define xpow(x, y) ((long)1 << y)
Hagrass 2:4fe211aae36e 12 const float ALTITUDE_EXPONENT = 1/5.255;
Hagrass 2:4fe211aae36e 13 const float ALTITUDE_PRESSURE_REFERENCE = 101325;
Hagrass 2:4fe211aae36e 14 const float ALTITUDE_COEFF = 44330.0;
Hagrass 2:4fe211aae36e 15 float BMP085::calcAltitude(int pressure) {
Hagrass 2:4fe211aae36e 16 //Compute an estimate of altitude
Hagrass 2:4fe211aae36e 17 // see page 15 of manual
Hagrass 2:4fe211aae36e 18 float float_comp_pressure = (float) pressure;
Hagrass 2:4fe211aae36e 19 float altitude = float_comp_pressure/ALTITUDE_PRESSURE_REFERENCE;
Hagrass 2:4fe211aae36e 20 altitude = pow(altitude, ALTITUDE_EXPONENT);
Hagrass 2:4fe211aae36e 21 altitude = 1.0 - altitude;
Hagrass 2:4fe211aae36e 22 altitude *= ALTITUDE_COEFF;
Hagrass 2:4fe211aae36e 23 // formula is: altitude = 44330 * (1-pow((p/p0), 1/5.255))
Hagrass 2:4fe211aae36e 24 return altitude;
Hagrass 2:4fe211aae36e 25 }
okini3939 0:dbba605ca87c 26
okini3939 0:dbba605ca87c 27 BMP085::BMP085 (PinName p_sda, PinName p_scl, BMP085_oss p_oss) : i2c(p_sda, p_scl) {
okini3939 0:dbba605ca87c 28 init(p_oss);
okini3939 0:dbba605ca87c 29 }
okini3939 0:dbba605ca87c 30
okini3939 0:dbba605ca87c 31 BMP085::BMP085 (I2C& p_i2c, BMP085_oss p_oss) : i2c(p_i2c) {
okini3939 0:dbba605ca87c 32 init(p_oss);
okini3939 0:dbba605ca87c 33 }
okini3939 0:dbba605ca87c 34
okini3939 0:dbba605ca87c 35 float BMP085::get_temperature() {
okini3939 0:dbba605ca87c 36 return temperature;
okini3939 0:dbba605ca87c 37 }
okini3939 0:dbba605ca87c 38
okini3939 0:dbba605ca87c 39 float BMP085::get_pressure() {
okini3939 0:dbba605ca87c 40 return pressure;
Hagrass 2:4fe211aae36e 41
okini3939 0:dbba605ca87c 42 }
okini3939 0:dbba605ca87c 43
okini3939 0:dbba605ca87c 44 void BMP085::update () {
okini3939 0:dbba605ca87c 45 long t, p, ut, up, x1, x2, x3, b3, b5, b6;
okini3939 0:dbba605ca87c 46 unsigned long b4, b7;
okini3939 0:dbba605ca87c 47
okini3939 0:dbba605ca87c 48 twi_writechar(WEATHER_BMP085, 0xf4, 0x2e);
okini3939 0:dbba605ca87c 49 wait(0.01);
okini3939 0:dbba605ca87c 50 ut = twi_readshort(WEATHER_BMP085, 0xf6);
okini3939 0:dbba605ca87c 51
okini3939 0:dbba605ca87c 52 twi_writechar(WEATHER_BMP085, 0xf4, 0x34 | (oss << 6));
okini3939 0:dbba605ca87c 53 wait(0.05);
okini3939 0:dbba605ca87c 54 up = twi_readlong(WEATHER_BMP085, 0xf6) >> (8 - oss);
okini3939 0:dbba605ca87c 55
okini3939 0:dbba605ca87c 56 x1 = (ut - ac6) * ac5 / xpow(2, 15);
okini3939 0:dbba605ca87c 57 x2 = (long)mc * xpow(2, 11) / (x1 + md);
okini3939 0:dbba605ca87c 58 b5 = x1 + x2;
okini3939 0:dbba605ca87c 59 t = (b5 + 8) / xpow(2, 4);
okini3939 0:dbba605ca87c 60 temperature = (float)t / 10.0;
okini3939 0:dbba605ca87c 61
okini3939 0:dbba605ca87c 62 b6 = b5 - 4000;
okini3939 0:dbba605ca87c 63 x1 = (b2 * (b6 * b6 / xpow(2, 12))) / xpow(2, 11);
okini3939 0:dbba605ca87c 64 x2 = ac2 * b6 / xpow(2, 11);
okini3939 0:dbba605ca87c 65 x3 = x1 + x2;
okini3939 0:dbba605ca87c 66 b3 = ((((unsigned long)ac1 * 4 + x3) << oss) + 2) / 4;
okini3939 0:dbba605ca87c 67 x1 = ac3 * b6 / xpow(2, 13);
okini3939 0:dbba605ca87c 68 x2 = (b1 * (b6 * b6 / xpow(2, 12))) / xpow(2, 16);
okini3939 0:dbba605ca87c 69 x3 = ((x1 + x2) + 2) / xpow(2, 2);
okini3939 0:dbba605ca87c 70 b4 = ac4 * (unsigned long)(x3 + 32768) / xpow(2, 15);
okini3939 0:dbba605ca87c 71 b7 = ((unsigned long)up - b3) * (50000 >> oss);
okini3939 0:dbba605ca87c 72 if (b7 < (unsigned long)0x80000000) {
okini3939 0:dbba605ca87c 73 p = (b7 * 2) / b4;
okini3939 0:dbba605ca87c 74 } else {
okini3939 0:dbba605ca87c 75 p = (b7 / b4) * 2;
okini3939 0:dbba605ca87c 76 }
okini3939 0:dbba605ca87c 77 x1 = (p / xpow(2, 8)) * (p / xpow(2, 8));
okini3939 0:dbba605ca87c 78 x1 = (x1 * 3038) / xpow(2, 16);
okini3939 0:dbba605ca87c 79 x2 = (-7357 * p) / xpow(2, 16);
okini3939 0:dbba605ca87c 80 p = p + (x1 + x2 + 3791) / xpow(2, 4);
okini3939 0:dbba605ca87c 81 pressure = (float)p / 100.0;
okini3939 0:dbba605ca87c 82 }
okini3939 0:dbba605ca87c 83
okini3939 0:dbba605ca87c 84 void BMP085::init (BMP085_oss p_oss) {
okini3939 0:dbba605ca87c 85 ac1 = twi_readshort(WEATHER_BMP085, 0xaa);
okini3939 0:dbba605ca87c 86 ac2 = twi_readshort(WEATHER_BMP085, 0xac);
okini3939 0:dbba605ca87c 87 ac3 = twi_readshort(WEATHER_BMP085, 0xae);
okini3939 0:dbba605ca87c 88 ac4 = twi_readshort(WEATHER_BMP085, 0xb0);
okini3939 0:dbba605ca87c 89 ac5 = twi_readshort(WEATHER_BMP085, 0xb2);
okini3939 0:dbba605ca87c 90 ac6 = twi_readshort(WEATHER_BMP085, 0xb4);
okini3939 0:dbba605ca87c 91 b1 = twi_readshort(WEATHER_BMP085, 0xb6);
okini3939 0:dbba605ca87c 92 b2 = twi_readshort(WEATHER_BMP085, 0xb8);
okini3939 0:dbba605ca87c 93 mb = twi_readshort(WEATHER_BMP085, 0xba);
okini3939 0:dbba605ca87c 94 mc = twi_readshort(WEATHER_BMP085, 0xbc);
okini3939 0:dbba605ca87c 95 md = twi_readshort(WEATHER_BMP085, 0xbe);
okini3939 0:dbba605ca87c 96 oss = p_oss;
okini3939 0:dbba605ca87c 97 }
okini3939 0:dbba605ca87c 98
okini3939 0:dbba605ca87c 99 unsigned short BMP085::twi_readshort (int id, int addr) {
okini3939 0:dbba605ca87c 100 unsigned short i;
okini3939 0:dbba605ca87c 101
okini3939 0:dbba605ca87c 102 i2c.start();
okini3939 0:dbba605ca87c 103 i2c.write(id);
okini3939 0:dbba605ca87c 104 i2c.write(addr);
okini3939 0:dbba605ca87c 105
okini3939 0:dbba605ca87c 106 i2c.start();
okini3939 0:dbba605ca87c 107 i2c.write(id | 1);
okini3939 0:dbba605ca87c 108 i = i2c.read(1) << 8;
okini3939 0:dbba605ca87c 109 i |= i2c.read(0);
okini3939 0:dbba605ca87c 110 i2c.stop();
okini3939 0:dbba605ca87c 111
okini3939 0:dbba605ca87c 112 return i;
okini3939 0:dbba605ca87c 113 }
okini3939 0:dbba605ca87c 114
okini3939 0:dbba605ca87c 115 unsigned long BMP085::twi_readlong (int id, int addr) {
okini3939 0:dbba605ca87c 116 unsigned long i;
okini3939 0:dbba605ca87c 117
okini3939 0:dbba605ca87c 118 i2c.start();
okini3939 0:dbba605ca87c 119 i2c.write(id);
okini3939 0:dbba605ca87c 120 i2c.write(addr);
okini3939 0:dbba605ca87c 121
okini3939 0:dbba605ca87c 122 i2c.start();
okini3939 0:dbba605ca87c 123 i2c.write(id | 1);
okini3939 0:dbba605ca87c 124 i = i2c.read(1) << 16;
okini3939 0:dbba605ca87c 125 i |= i2c.read(1) << 8;
okini3939 0:dbba605ca87c 126 i |= i2c.read(0);
okini3939 0:dbba605ca87c 127 i2c.stop();
okini3939 0:dbba605ca87c 128
okini3939 0:dbba605ca87c 129 return i;
okini3939 0:dbba605ca87c 130 }
okini3939 0:dbba605ca87c 131
okini3939 1:1d88eb9f5bbd 132 void BMP085::twi_writechar (int id, int addr, int dat) {
okini3939 0:dbba605ca87c 133
okini3939 0:dbba605ca87c 134 i2c.start();
okini3939 0:dbba605ca87c 135 i2c.write(id);
okini3939 0:dbba605ca87c 136 i2c.write(addr);
okini3939 0:dbba605ca87c 137 i2c.write(dat);
okini3939 0:dbba605ca87c 138 i2c.stop();
okini3939 0:dbba605ca87c 139 }