1 | /***************************************************************************
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2 | This is a library for the BME280 humidity, temperature & pressure sensor
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3 |
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4 | Designed specifically to work with the Adafruit BME280 Breakout
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5 | ----> http://www.adafruit.com/products/2650
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6 |
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7 | These sensors use I2C or SPI to communicate, 2 or 4 pins are required
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8 | to interface.
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9 |
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10 | Adafruit invests time and resources providing this open source code,
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11 | please support Adafruit andopen-source hardware by purchasing products
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12 | from Adafruit!
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13 |
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14 | Written by Limor Fried & Kevin Townsend for Adafruit Industries.
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15 | BSD license, all text above must be included in any redistribution
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16 | ***************************************************************************/
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17 | #include "Arduino.h"
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18 | #include <Wire.h>
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19 | #include "BME280.h"
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20 |
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21 |
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22 | /***************************************************************************
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23 | PRIVATE FUNCTIONS
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24 | ***************************************************************************/
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25 |
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26 |
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27 | bool BME280::begin(uint8_t a) {
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28 | _i2caddr = a;
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29 |
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30 | if (read8(BME280_REGISTER_CHIPID) != 0x60)
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31 | return false;
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32 |
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33 | readCoefficients();
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34 |
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35 | //Set before CONTROL_meas (DS 5.4.3)
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36 | write8(BME280_REGISTER_CONTROLHUMID, 0x05); //16x oversampling
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37 |
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38 | write8(BME280_REGISTER_CONTROL, 0xB7); // 16x ovesampling, normal mode
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39 | return true;
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40 | }
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41 |
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42 |
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43 | /**************************************************************************/
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44 | /*!
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45 | @brief Writes an 8 bit value over I2C/SPI
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46 | */
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47 | /**************************************************************************/
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48 | void BME280::write8(byte reg, byte value)
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49 | {
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50 | Wire.beginTransmission((uint8_t)_i2caddr);
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51 | Wire.write((uint8_t)reg);
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52 | Wire.write((uint8_t)value);
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53 | Wire.endTransmission();
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54 | }
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55 |
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56 | /**************************************************************************/
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57 | /*!
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58 | @brief Reads an 8 bit value over I2C
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59 | */
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60 | /**************************************************************************/
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61 | uint8_t BME280::read8(byte reg)
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62 | {
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63 | uint8_t value;
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64 |
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65 | Wire.beginTransmission((uint8_t)_i2caddr);
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66 | Wire.write((uint8_t)reg);
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67 | Wire.endTransmission();
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68 | Wire.requestFrom((uint8_t)_i2caddr, (byte)1);
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69 | value = Wire.read();
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70 | return value;
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71 | }
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72 |
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73 | /**************************************************************************/
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74 | /*!
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75 | @brief Reads a 16 bit value over I2C
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76 | */
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77 | /**************************************************************************/
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78 | uint16_t BME280::read16(byte reg)
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79 | {
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80 | uint16_t value;
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81 |
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82 | Wire.beginTransmission((uint8_t)_i2caddr);
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83 | Wire.write((uint8_t)reg);
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84 | Wire.endTransmission();
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85 | Wire.requestFrom((uint8_t)_i2caddr, (byte)2);
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86 | value = (Wire.read() << 8) | Wire.read();
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87 |
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88 | return value;
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89 | }
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90 |
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91 | uint16_t BME280::read16_LE(byte reg) {
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92 | uint16_t temp = read16(reg);
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93 | return (temp >> 8) | (temp << 8);
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94 |
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95 | }
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96 |
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97 | /**************************************************************************/
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98 | /*!
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99 | @brief Reads a signed 16 bit value over I2C
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100 | */
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101 | /**************************************************************************/
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102 | int16_t BME280::readS16(byte reg)
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103 | {
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104 | return (int16_t)read16(reg);
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105 |
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106 | }
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107 |
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108 | int16_t BME280::readS16_LE(byte reg)
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109 | {
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110 | return (int16_t)read16_LE(reg);
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111 |
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112 | }
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113 |
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114 |
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115 | /**************************************************************************/
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116 | /*!
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117 | @brief Reads a 24 bit value over I2C
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118 | */
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119 | /**************************************************************************/
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120 |
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121 | uint32_t BME280::read24(byte reg)
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122 | {
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123 | uint32_t value;
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124 |
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125 | Wire.beginTransmission((uint8_t)_i2caddr);
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126 | Wire.write((uint8_t)reg);
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127 | Wire.endTransmission();
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128 | Wire.requestFrom((uint8_t)_i2caddr, (byte)3);
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129 |
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130 | value = Wire.read();
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131 | value <<= 8;
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132 | value |= Wire.read();
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133 | value <<= 8;
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134 | value |= Wire.read();
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135 |
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136 | return value;
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137 | }
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138 |
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139 |
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140 | /**************************************************************************/
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141 | /*!
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142 | @brief Reads the factory-set coefficients
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143 | */
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144 | /**************************************************************************/
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145 | void BME280::readCoefficients(void)
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146 | {
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147 | _bme280_calib.dig_T1 = read16_LE(BME280_REGISTER_DIG_T1);
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148 | _bme280_calib.dig_T2 = readS16_LE(BME280_REGISTER_DIG_T2);
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149 | _bme280_calib.dig_T3 = readS16_LE(BME280_REGISTER_DIG_T3);
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150 |
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151 | _bme280_calib.dig_P1 = read16_LE(BME280_REGISTER_DIG_P1);
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152 | _bme280_calib.dig_P2 = readS16_LE(BME280_REGISTER_DIG_P2);
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153 | _bme280_calib.dig_P3 = readS16_LE(BME280_REGISTER_DIG_P3);
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154 | _bme280_calib.dig_P4 = readS16_LE(BME280_REGISTER_DIG_P4);
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155 | _bme280_calib.dig_P5 = readS16_LE(BME280_REGISTER_DIG_P5);
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156 | _bme280_calib.dig_P6 = readS16_LE(BME280_REGISTER_DIG_P6);
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157 | _bme280_calib.dig_P7 = readS16_LE(BME280_REGISTER_DIG_P7);
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158 | _bme280_calib.dig_P8 = readS16_LE(BME280_REGISTER_DIG_P8);
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159 | _bme280_calib.dig_P9 = readS16_LE(BME280_REGISTER_DIG_P9);
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160 |
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161 | _bme280_calib.dig_H1 = read8(BME280_REGISTER_DIG_H1);
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162 | _bme280_calib.dig_H2 = readS16_LE(BME280_REGISTER_DIG_H2);
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163 | _bme280_calib.dig_H3 = read8(BME280_REGISTER_DIG_H3);
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164 | _bme280_calib.dig_H4 = (read8(BME280_REGISTER_DIG_H4) << 4) | (read8(BME280_REGISTER_DIG_H4+1) & 0xF);
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165 | _bme280_calib.dig_H5 = (read8(BME280_REGISTER_DIG_H5+1) << 4) | (read8(BME280_REGISTER_DIG_H5) >> 4);
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166 | _bme280_calib.dig_H6 = (int8_t)read8(BME280_REGISTER_DIG_H6);
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167 | }
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168 |
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169 | /**************************************************************************/
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170 | /*!
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171 |
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172 | */
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173 | /**************************************************************************/
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174 | float BME280::temperature(void)
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175 | {
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176 | int32_t var1, var2;
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177 |
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178 | int32_t adc_T = read24(BME280_REGISTER_TEMPDATA);
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179 | adc_T >>= 4;
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180 |
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181 | var1 = ((((adc_T>>3) - ((int32_t)_bme280_calib.dig_T1 <<1))) *
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182 | ((int32_t)_bme280_calib.dig_T2)) >> 11;
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183 |
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184 | var2 = (((((adc_T>>4) - ((int32_t)_bme280_calib.dig_T1)) *
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185 | ((adc_T>>4) - ((int32_t)_bme280_calib.dig_T1))) >> 12) *
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186 | ((int32_t)_bme280_calib.dig_T3)) >> 14;
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187 |
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188 | t_fine = var1 + var2;
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189 |
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190 | float T = (t_fine * 5 + 128) >> 8;
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191 | return T/100;
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192 | }
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193 |
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194 | /**************************************************************************/
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195 | /*!
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196 |
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197 | */
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198 | /**************************************************************************/
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199 | float BME280::pressure(void) {
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200 | int64_t var1, var2, p;
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201 |
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202 | temperature(); // must be done first to get t_fine
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203 |
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204 | int32_t adc_P = read24(BME280_REGISTER_PRESSUREDATA);
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205 | adc_P >>= 4;
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206 |
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207 | var1 = ((int64_t)t_fine) - 128000;
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208 | var2 = var1 * var1 * (int64_t)_bme280_calib.dig_P6;
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209 | var2 = var2 + ((var1*(int64_t)_bme280_calib.dig_P5)<<17);
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210 | var2 = var2 + (((int64_t)_bme280_calib.dig_P4)<<35);
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211 | var1 = ((var1 * var1 * (int64_t)_bme280_calib.dig_P3)>>8) +
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212 | ((var1 * (int64_t)_bme280_calib.dig_P2)<<12);
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213 | var1 = (((((int64_t)1)<<47)+var1))*((int64_t)_bme280_calib.dig_P1)>>33;
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214 |
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215 | if (var1 == 0) {
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216 | return 0; // avoid exception caused by division by zero
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217 | }
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218 | p = 1048576 - adc_P;
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219 | p = (((p<<31) - var2)*3125) / var1;
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220 | var1 = (((int64_t)_bme280_calib.dig_P9) * (p>>13) * (p>>13)) >> 25;
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221 | var2 = (((int64_t)_bme280_calib.dig_P8) * p) >> 19;
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222 |
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223 | p = ((p + var1 + var2) >> 8) + (((int64_t)_bme280_calib.dig_P7)<<4);
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224 | return (float)p/256;
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225 | }
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226 |
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227 |
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228 | /**************************************************************************/
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229 | /*!
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230 |
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231 | */
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232 | /**************************************************************************/
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233 | float BME280::humidity(void) {
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234 |
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235 | temperature(); // must be done first to get t_fine
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236 |
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237 | int32_t adc_H = read16(BME280_REGISTER_HUMIDDATA);
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238 |
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239 | int32_t v_x1_u32r;
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240 |
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241 | v_x1_u32r = (t_fine - ((int32_t)76800));
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242 |
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243 | v_x1_u32r = (((((adc_H << 14) - (((int32_t)_bme280_calib.dig_H4) << 20) -
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244 | (((int32_t)_bme280_calib.dig_H5) * v_x1_u32r)) + ((int32_t)16384)) >> 15) *
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245 | (((((((v_x1_u32r * ((int32_t)_bme280_calib.dig_H6)) >> 10) *
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246 | (((v_x1_u32r * ((int32_t)_bme280_calib.dig_H3)) >> 11) + ((int32_t)32768))) >> 10) +
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247 | ((int32_t)2097152)) * ((int32_t)_bme280_calib.dig_H2) + 8192) >> 14));
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248 |
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249 | v_x1_u32r = (v_x1_u32r - (((((v_x1_u32r >> 15) * (v_x1_u32r >> 15)) >> 7) *
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250 | ((int32_t)_bme280_calib.dig_H1)) >> 4));
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251 |
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252 | v_x1_u32r = (v_x1_u32r < 0) ? 0 : v_x1_u32r;
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253 | v_x1_u32r = (v_x1_u32r > 419430400) ? 419430400 : v_x1_u32r;
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254 | float h = (v_x1_u32r>>12);
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255 | return h / 1024.0;
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256 | }
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257 |
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258 | /**************************************************************************/
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259 | /*!
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260 | Calculates the altitude (in meters) from the specified atmospheric
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261 | pressure (in hPa), and sea-level pressure (in hPa).
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262 |
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263 | @param seaLevel Sea-level pressure in hPa
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264 | @param atmospheric Atmospheric pressure in hPa
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265 | */
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266 | /**************************************************************************/
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267 | float BME280::altitude(float seaLevel)
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268 | {
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269 | // Equation taken from BMP180 datasheet (page 16):
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270 | // http://www.adafruit.com/datasheets/BST-BMP180-DS000-09.pdf
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271 |
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272 | // Note that using the equation from wikipedia can give bad results
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273 | // at high altitude. See this thread for more information:
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274 | // http://forums.adafruit.com/viewtopic.php?f=22&t=58064
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275 |
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276 | float atmospheric = pressure() / 100.0F;
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277 | return 44330.0 * (1.0 - pow(atmospheric / seaLevel, 0.1903));
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278 | }
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279 |
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280 | BME280 bme280;
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