bme280.h

00001 /*
00002   bme280.h - driver for Bosch Sensortec BME280 combined humidity and pressure sensor.
00003 
00004   Copyright (c) 2015 Elektor
00005 
00006   26/11/2015 - CPV, Initial release.
00007   
00008   This library is free software; you can redistribute it and/or
00009   modify it under the terms of the GNU Lesser General Public
00010   License as published by the Free Software Foundation; either
00011   version 2.1 of the License, or (at your option) any later version.
00012 
00013   This library is distributed in the hope that it will be useful,
00014   but WITHOUT ANY WARRANTY; without even the implied warranty of
00015   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00016   Lesser General Public License for more details.
00017 
00018   You should have received a copy of the GNU Lesser General
00019   Public License along with this library; if not, write to the
00020   Free Software Foundation, Inc., 59 Temple Place, Suite 330,
00021   Boston, MA  02111-1307  USA
00022 
00023 */
00024 
00025 #ifndef __BME280_H__
00026 #define __BME280_H__
00027 
00028 #include <stdint.h>
00029 
00030 
00031 #define BME280_ALLOW_FLOAT  (1)
00032 
00033 #if BME280_ALLOW_FLOAT!=0
00034   typedef double temperature_t;
00035   typedef double pressure_t;
00036   typedef double humidity_t;
00037 #else
00038   typedef int32_t temperature_t;
00039   typedef uint32_t pressure_t;
00040   typedef uint32_t humidity_t;
00041 #endif /* BME280_ALLOW_FLOAT */
00042 
00043 
00044 // Two possible addresses, depending on level on SDO pin.
00045 #define BME280_I2C_ADDRESS1  (0x76)
00046 #define BME280_I2C_ADDRESS2  (0x77)
00047 
00048 // Calibration registers.
00049 #define BME280_CAL_T1  (0x88)
00050 #define BME280_CAL_T2  (0x8a)
00051 #define BME280_CAL_T3  (0x8c)
00052 #define BME280_CAL_P1  (0x8e)
00053 #define BME280_CAL_P2  (0x90)
00054 #define BME280_CAL_P3  (0x92)
00055 #define BME280_CAL_P4  (0x94)
00056 #define BME280_CAL_P5  (0x96)
00057 #define BME280_CAL_P6  (0x98)
00058 #define BME280_CAL_P7  (0x9a)
00059 #define BME280_CAL_P8  (0x9c)
00060 #define BME280_CAL_P9  (0x9e)
00061 #define BME280_CAL_H1  (0xa1) /* 8 bits */
00062 #define BME280_CAL_H2  (0xe1)
00063 #define BME280_CAL_H3  (0xe3) /* 8 bits */
00064 #define BME280_CAL_H4  (0xe4) /* 12 bits, combined with H45 */
00065 #define BME280_CAL_H45  (0xe5) /* 12 bits, combined with H5 */
00066 #define BME280_CAL_H5  (0xe6) /* 8 bits */
00067 #define BME280_CAL_H6  (0xe7) /* 8 bits */
00068 
00069 // Control registers.
00070 #define BME280_ID_REGISTER  (0xd0) /* 8 bits */
00071 #define BME280_RESET_REGISTER  (0xe0) /* 8 bits */
00072 #define BME280_CTRL_HUM_REGISTER  (0xf2) /* 8 bits */
00073 #define BME280_STATUS_REGISTER  (0xf3) /* 8 bits */
00074 #define BME280_CTRL_MEAS_REGISTER  (0xf4) /* 8 bits */
00075 #define BME280_CONFIG_REGISTER  (0xf5) /* 8 bits */
00076 
00077 // Measurement registers.
00078 #define BME280_PRESSURE  (0xf7) /* 20 bits */
00079 #define BME280_PRESSURE_MSB  (0xf7) /* 8 bits */
00080 #define BME280_PRESSURE_LSB  (0xf8) /* 8 bits */
00081 #define BME280_PRESSURE_XLSB  (0xf9) /* 8 bits */
00082 #define BME280_TEMPERATURE  (0xfa) /* 20 bits */
00083 #define BME280_TEMPERATURE_MSB  (0xfa) /* 8 bits */
00084 #define BME280_TEMPERATURE_LSB  (0xfb) /* 8 bits */
00085 #define BME280_TEMPERATURE_XLSB  (0xfc) /* 8 bits */
00086 #define BME280_HUMIDITY  (0xfd) /* 16 bits */
00087 #define BME280_HUMIDITY_MSB  (0xfd) /* 8 bits */
00088 #define BME280_HUMIDITY_LSB  (0xfe) /* 8 bits */
00089 
00090 // It is recommended to read all the measurements in one go.
00091 #define BME280_MEASUREMENT_REGISTER  (BME280_PRESSURE)
00092 #define BME280_MEASUREMENT_SIZE  (8)
00093 
00094 // Values for osrs_p & osrs_t fields of CTRL_MEAS register.
00095 #define BME280_SKIP  (0)
00096 #define BME280_OVERSAMPLING_1X  (1)
00097 #define BME280_OVERSAMPLING_2X  (2)
00098 #define BME280_OVERSAMPLING_4X  (3)
00099 #define BME280_OVERSAMPLING_8X  (4)
00100 #define BME280_OVERSAMPLING_16X  (5)
00101 
00102 // Values for mode field of CTRL_MEAS register.
00103 #define BME280_MODE_SLEEP  (0)
00104 #define BME280_MODE_FORCED  (1)
00105 #define BME280_MODE_NORMAL  (3)
00106 
00107 // Value for RESET register.
00108 #define BME280_RESET  (0xb6)
00109 
00110 // Value of ID register.
00111 #define BME280_ID  (0x60)
00112 
00113 // Values for t_sb field of CONFIG register
00114 #define BME280_STANDBY_500_US  (0)
00115 #define BME280_STANDBY_10_MS  (6)
00116 #define BME280_STANDBY_20_MS  (7)
00117 #define BME280_STANDBY_63_MS  (1)
00118 #define BME280_STANDBY_125_MS  (2)
00119 #define BME280_STANDBY_250_MS  (3)
00120 #define BME280_STANDBY_500_MS  (4)
00121 #define BME280_STANDBY_1000_MS  (5)
00122 
00123 // Values for filter field of CONFIG register
00124 #define BME280_FILTER_OFF  (0)
00125 #define BME280_FILTER_COEFF_2  (1)
00126 #define BME280_FILTER_COEFF_4  (2)
00127 #define BME280_FILTER_COEFF_8  (3)
00128 #define BME280_FILTER_COEFF_16  (4)
00129 
00130 
00131 // I2C write function must support repeated start to avoid interruption of transactions.
00132 // User-provided function to write data_size bytes from buffer p_data to I2C device at bus address i2c_address.
00133 // Provide empty function if not used.
00134 extern void i2cWrite(uint8_t i2c_address, uint8_t *p_data, uint8_t data_size, uint8_t repeated_start);
00135 // User-provided function to read data_size bytes from I2C device at bus address i2c_address to buffer p_data.
00136 // Provide empty function if not used.
00137 extern void i2cRead(uint8_t i2c_address, uint8_t *p_data, uint8_t data_size);
00138 
00139 // SPI functions must activate (make low) BME280 CSB pin before doing a transfer
00140 // and deactivate it (make high) when done.
00141 // User-provided function to write data_size bytes from buffer p_data to SPI device.
00142 // Provide empty function if not used.
00143 extern void spiWrite(uint8_t *p_data, uint8_t data_size);
00144 // User-provided function to read data_size bytes from SPI device to buffer p_data.
00145 // Provide empty function if not used.
00146 extern void spiRead(uint8_t *p_data, uint8_t data_size);
00147 
00148 
00149 class BME280
00150 {
00151 public:
00152   BME280(void);
00153   uint8_t begin(uint8_t i2cAddress=0); // I2C address not set means SPI.
00154 
00155   void readCalibrationData(void);
00156   uint8_t readId(void);
00157   uint8_t readFrom(uint8_t reg, uint8_t data_size, uint8_t *p_data);
00158 
00159   void read(void);
00160 
00161   // If using floating points, values are scaled, if not then
00162   // temperature is 100*T, pressure is Pa en humidity is 1024*%RH
00163   temperature_t temperature(void) { return _temperature; } // [degrees Celsius] or 100*[degrees Celsius]
00164   pressure_t pressure(void) { return _pressure; } // [Pa]
00165   humidity_t humidity(void) { return _humidity; } // [%RH] or 1024*[%RH]
00166 
00167   void writeControlRegisters(uint8_t osrs_t, uint8_t osrs_p, uint8_t osrs_h, uint8_t mode);
00168   void writeConfigRegister(uint8_t t_sb, uint8_t filter, uint8_t spi);
00169 
00170   void reset(void);
00171 
00172 private:
00173   uint8_t _i2c_address;
00174 
00175   void busWrite(uint8_t *p_data, uint8_t data_size, uint8_t repeated_start);
00176   void busRead(uint8_t *p_data, uint8_t data_size);
00177 
00178   // Calibration data.
00179   uint16_t _dig_T1;
00180   int16_t _dig_T2;
00181   int16_t _dig_T3;
00182   uint16_t _dig_P1;
00183   int16_t _dig_P2;
00184   int16_t _dig_P3;
00185   int16_t _dig_P4;
00186   int16_t _dig_P5;
00187   int16_t _dig_P6;
00188   int16_t _dig_P7;
00189   int16_t _dig_P8;
00190   int16_t _dig_P9;
00191   uint8_t _dig_H1;
00192   int16_t _dig_H2;
00193   uint8_t _dig_H3;
00194   int16_t _dig_H4;
00195   int16_t _dig_H5;
00196   int8_t _dig_H6;
00197   void clearCalibrationData(void);
00198 
00199   uint8_t readUint8(uint8_t reg);
00200   uint16_t readUint16(uint8_t reg);
00201 
00202   int32_t assembleRawValue(uint8_t *p_data, uint8_t has_xlsb);
00203 
00204   int32_t _t_fine;
00205 
00206   temperature_t compensateTemperature(int32_t adc_T);
00207   pressure_t compensatePressure(int32_t adc_P);
00208   humidity_t compensateHumidity(int32_t adc_H);
00209 
00210   temperature_t _temperature;
00211   pressure_t _pressure;
00212   humidity_t _humidity;
00213 };
00214 
00215 
00216 #endif /* __BME280_H__*/