Taijun Kozarashi / BMP085

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Fork of myBMP085 by Taijun Kozarashi

BMP085.cpp@0:b9870f4bc956, 2014-06-05 (annotated)

Committer:
stepJun
Date:
Thu Jun 05 12:02:46 2014 +0000
Revision:
0:b9870f4bc956
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Who changed what in which revision?

UserRevisionLine numberNew contents of line
stepJun 0:b9870f4bc956 1 /*
stepJun 0:b9870f4bc956 2 * mbed library to use a Bosch Sensortec BMP085 sensor
stepJun 0:b9870f4bc956 3 * Copyright (c) 2010 Hiroshi Suga
stepJun 0:b9870f4bc956 4 * Released under the MIT License: http://mbed.org/license/mit
stepJun 0:b9870f4bc956 5 */
stepJun 0:b9870f4bc956 6
stepJun 0:b9870f4bc956 7 #include "mbed.h"
stepJun 0:b9870f4bc956 8 #include "BMP085.h"
stepJun 0:b9870f4bc956 9
stepJun 0:b9870f4bc956 10 #define WEATHER_BMP085 0xee
stepJun 0:b9870f4bc956 11 #define xpow(x, y) ((long)1 << y)
stepJun 0:b9870f4bc956 12
stepJun 0:b9870f4bc956 13
stepJun 0:b9870f4bc956 14 BMP085::BMP085 (PinName p_sda, PinName p_scl, BMP085_oss p_oss) : i2c(p_sda, p_scl) {
stepJun 0:b9870f4bc956 15 init(p_oss);
stepJun 0:b9870f4bc956 16 }
stepJun 0:b9870f4bc956 17
stepJun 0:b9870f4bc956 18 BMP085::BMP085 (I2C& p_i2c, BMP085_oss p_oss) : i2c(p_i2c) {
stepJun 0:b9870f4bc956 19 init(p_oss);
stepJun 0:b9870f4bc956 20 }
stepJun 0:b9870f4bc956 21
stepJun 0:b9870f4bc956 22 float BMP085::get_temperature() {
stepJun 0:b9870f4bc956 23 return temperature;
stepJun 0:b9870f4bc956 24 }
stepJun 0:b9870f4bc956 25
stepJun 0:b9870f4bc956 26 long BMP085::get_pressure() {
stepJun 0:b9870f4bc956 27 return pressure;
stepJun 0:b9870f4bc956 28 }
stepJun 0:b9870f4bc956 29
stepJun 0:b9870f4bc956 30 void BMP085::update () {
stepJun 0:b9870f4bc956 31 long t, p, ut, up, x1, x2, x3, b3, b5, b6;
stepJun 0:b9870f4bc956 32 unsigned long b4, b7;
stepJun 0:b9870f4bc956 33
stepJun 0:b9870f4bc956 34 twi_writechar(WEATHER_BMP085, 0xf4, 0x2e);
stepJun 0:b9870f4bc956 35 wait(0.0045);
stepJun 0:b9870f4bc956 36 ut = twi_readshort(WEATHER_BMP085, 0xf6);
stepJun 0:b9870f4bc956 37
stepJun 0:b9870f4bc956 38 twi_writechar(WEATHER_BMP085, 0xf4, 0x34 | (oss << 6));
stepJun 0:b9870f4bc956 39 wait(0.0075);
stepJun 0:b9870f4bc956 40 up = twi_readlong(WEATHER_BMP085, 0xf6) >> (8 - oss);
stepJun 0:b9870f4bc956 41
stepJun 0:b9870f4bc956 42 x1 = (ut - ac6) * ac5 / xpow(2, 15);
stepJun 0:b9870f4bc956 43 x2 = (long)mc * xpow(2, 11) / (x1 + md);
stepJun 0:b9870f4bc956 44 b5 = x1 + x2;
stepJun 0:b9870f4bc956 45 t = (b5 + 8) / xpow(2, 4);
stepJun 0:b9870f4bc956 46 temperature = (float)t / 10.0;
stepJun 0:b9870f4bc956 47
stepJun 0:b9870f4bc956 48 b6 = b5 - 4000;
stepJun 0:b9870f4bc956 49 x1 = (b2 * (b6 * b6 / xpow(2, 12))) / xpow(2, 11);
stepJun 0:b9870f4bc956 50 x2 = ac2 * b6 / xpow(2, 11);
stepJun 0:b9870f4bc956 51 x3 = x1 + x2;
stepJun 0:b9870f4bc956 52 b3 = ((((unsigned long)ac1 * 4 + x3) << oss) + 2) / 4;
stepJun 0:b9870f4bc956 53 x1 = ac3 * b6 / xpow(2, 13);
stepJun 0:b9870f4bc956 54 x2 = (b1 * (b6 * b6 / xpow(2, 12))) / xpow(2, 16);
stepJun 0:b9870f4bc956 55 x3 = ((x1 + x2) + 2) / xpow(2, 2);
stepJun 0:b9870f4bc956 56 b4 = ac4 * (unsigned long)(x3 + 32768) / xpow(2, 15);
stepJun 0:b9870f4bc956 57 b7 = ((unsigned long)up - b3) * (50000 >> oss);
stepJun 0:b9870f4bc956 58 if (b7 < (unsigned long)0x80000000) {
stepJun 0:b9870f4bc956 59 p = (b7 * 2) / b4;
stepJun 0:b9870f4bc956 60 } else {
stepJun 0:b9870f4bc956 61 p = (b7 / b4) * 2;
stepJun 0:b9870f4bc956 62 }
stepJun 0:b9870f4bc956 63 x1 = (p / xpow(2, 8)) * (p / xpow(2, 8));
stepJun 0:b9870f4bc956 64 x1 = (x1 * 3038) / xpow(2, 16);
stepJun 0:b9870f4bc956 65 x2 = (-7357 * p) / xpow(2, 16);
stepJun 0:b9870f4bc956 66 p = p + (x1 + x2 + 3791) / xpow(2, 4);
stepJun 0:b9870f4bc956 67 pressure = (long)p;
stepJun 0:b9870f4bc956 68 }
stepJun 0:b9870f4bc956 69
stepJun 0:b9870f4bc956 70 void BMP085::init (BMP085_oss p_oss) {
stepJun 0:b9870f4bc956 71 ac1 = twi_readshort(WEATHER_BMP085, 0xaa);
stepJun 0:b9870f4bc956 72 ac2 = twi_readshort(WEATHER_BMP085, 0xac);
stepJun 0:b9870f4bc956 73 ac3 = twi_readshort(WEATHER_BMP085, 0xae);
stepJun 0:b9870f4bc956 74 ac4 = twi_readshort(WEATHER_BMP085, 0xb0);
stepJun 0:b9870f4bc956 75 ac5 = twi_readshort(WEATHER_BMP085, 0xb2);
stepJun 0:b9870f4bc956 76 ac6 = twi_readshort(WEATHER_BMP085, 0xb4);
stepJun 0:b9870f4bc956 77 b1 = twi_readshort(WEATHER_BMP085, 0xb6);
stepJun 0:b9870f4bc956 78 b2 = twi_readshort(WEATHER_BMP085, 0xb8);
stepJun 0:b9870f4bc956 79 mb = twi_readshort(WEATHER_BMP085, 0xba);
stepJun 0:b9870f4bc956 80 mc = twi_readshort(WEATHER_BMP085, 0xbc);
stepJun 0:b9870f4bc956 81 md = twi_readshort(WEATHER_BMP085, 0xbe);
stepJun 0:b9870f4bc956 82 oss = p_oss;
stepJun 0:b9870f4bc956 83 }
stepJun 0:b9870f4bc956 84
stepJun 0:b9870f4bc956 85 unsigned short BMP085::twi_readshort (int id, int addr) {
stepJun 0:b9870f4bc956 86 unsigned short i;
stepJun 0:b9870f4bc956 87
stepJun 0:b9870f4bc956 88 i2c.start();
stepJun 0:b9870f4bc956 89 i2c.write(id);
stepJun 0:b9870f4bc956 90 i2c.write(addr);
stepJun 0:b9870f4bc956 91
stepJun 0:b9870f4bc956 92 i2c.start();
stepJun 0:b9870f4bc956 93 i2c.write(id | 1);
stepJun 0:b9870f4bc956 94 i = i2c.read(1) << 8;
stepJun 0:b9870f4bc956 95 i |= i2c.read(0);
stepJun 0:b9870f4bc956 96 i2c.stop();
stepJun 0:b9870f4bc956 97
stepJun 0:b9870f4bc956 98 return i;
stepJun 0:b9870f4bc956 99 }
stepJun 0:b9870f4bc956 100
stepJun 0:b9870f4bc956 101 unsigned long BMP085::twi_readlong (int id, int addr) {
stepJun 0:b9870f4bc956 102 unsigned long i;
stepJun 0:b9870f4bc956 103
stepJun 0:b9870f4bc956 104 i2c.start();
stepJun 0:b9870f4bc956 105 i2c.write(id);
stepJun 0:b9870f4bc956 106 i2c.write(addr);
stepJun 0:b9870f4bc956 107
stepJun 0:b9870f4bc956 108 i2c.start();
stepJun 0:b9870f4bc956 109 i2c.write(id | 1);
stepJun 0:b9870f4bc956 110 i = i2c.read(1) << 16;
stepJun 0:b9870f4bc956 111 i |= i2c.read(1) << 8;
stepJun 0:b9870f4bc956 112 i |= i2c.read(0);
stepJun 0:b9870f4bc956 113 i2c.stop();
stepJun 0:b9870f4bc956 114
stepJun 0:b9870f4bc956 115 return i;
stepJun 0:b9870f4bc956 116 }
stepJun 0:b9870f4bc956 117
stepJun 0:b9870f4bc956 118 void BMP085::twi_writechar (int id, int addr, int dat) {
stepJun 0:b9870f4bc956 119
stepJun 0:b9870f4bc956 120 i2c.start();
stepJun 0:b9870f4bc956 121 i2c.write(id);
stepJun 0:b9870f4bc956 122 i2c.write(addr);
stepJun 0:b9870f4bc956 123 i2c.write(dat);
stepJun 0:b9870f4bc956 124 i2c.stop();
stepJun 0:b9870f4bc956 125 }