BMP280.h

00001 #ifndef BMP280_H
00002 #define BMP280_H
00003  
00004 //#include "mbed.h"
00005 
00006 // BMP280 registers
00007 #define BMP280_TEMP_XLSB  0xFC
00008 #define BMP280_TEMP_LSB   0xFB
00009 #define BMP280_TEMP_MSB   0xFA
00010 #define BMP280_PRESS_XLSB 0xF9
00011 #define BMP280_PRESS_LSB  0xF8
00012 #define BMP280_PRESS_MSB  0xF7
00013 #define BMP280_CONFIG     0xF5
00014 #define BMP280_CTRL_MEAS  0xF4
00015 #define BMP280_STATUS     0xF3
00016 #define BMP280_RESET      0xE0
00017 #define BMP280_ID         0xD0  // should be 0x58
00018 #define BMP280_CALIB00    0x88
00019 #define BMP280_ADDRESS 0x77<<1
00020 
00021 // Set initial input parameters
00022 
00023 enum Posr {
00024   P_OSR_00 = 0,  // no op
00025   P_OSR_01,
00026   P_OSR_02,
00027   P_OSR_04,
00028   P_OSR_08,
00029   P_OSR_16
00030 };
00031 
00032 enum Tosr {
00033   T_OSR_00 = 0,  // no op
00034   T_OSR_01,
00035   T_OSR_02,
00036   T_OSR_04,
00037   T_OSR_08,
00038   T_OSR_16
00039 };
00040 
00041 enum IIRFilter {
00042   full = 0,  // bandwidth at full sample rate
00043   BW0_223ODR,
00044   BW0_092ODR,
00045   BW0_042ODR,
00046   BW0_021ODR // bandwidth at 0.021 x sample rate
00047 };
00048 
00049 enum Mode {
00050   BMP280Sleep = 0,
00051   forced,
00052   forced2,
00053   normal
00054 };
00055 
00056 enum SBy {
00057   t_00_5ms = 0,
00058   t_62_5ms,
00059   t_125ms,
00060   t_250ms,
00061   t_500ms,
00062   t_1000ms,
00063   t_2000ms,
00064   t_4000ms,
00065 };
00066 
00067 // Specify BMP280 configuration
00068 uint8_t Posr = P_OSR_16, Tosr = T_OSR_02, Mode = normal, IIRFilter = BW0_042ODR, SBy = t_62_5ms;     // set pressure amd temperature output data rate
00069 // t_fine carries fine temperature as global value for BMP280
00070 int32_t t_fine;
00071 
00072 //Set up I2C, (SDA,SCL)
00073 //I2C i2c(P0_0, P0_1);
00074     
00075 // BMP280 compensation parameters
00076 uint16_t dig_T1, dig_P1;
00077 int16_t  dig_T2, dig_T3, dig_P2, dig_P3, dig_P4, dig_P5, dig_P6, dig_P7, dig_P8, dig_P9;
00078 
00079 class BMP280 {
00080  
00081     protected:
00082  
00083     public:
00084   //===================================================================================================================
00085 //====== Set of useful function to access pressure and temperature data
00086 //===================================================================================================================
00087 
00088     
00089     void writeByte(uint8_t address, uint8_t subAddress, uint8_t data)
00090 {
00091    char data_write[2];
00092    data_write[0] = subAddress;
00093    data_write[1] = data;
00094    i2c.write(address, data_write, 2, 0);
00095 }
00096 
00097     char readByte(uint8_t address, uint8_t subAddress)
00098 {
00099     char data[1]; // `data` will store the register data     
00100     char data_write[1];
00101     data_write[0] = subAddress;
00102     i2c.write(address, data_write, 1, 1); // no stop
00103     i2c.read(address, data, 1, 0); 
00104     return data[0]; 
00105 }
00106 
00107     void readBytes(uint8_t address, uint8_t subAddress, uint8_t count, uint8_t * dest)
00108 {     
00109     char data[24];
00110     char data_write[1];
00111     data_write[0] = subAddress;
00112     i2c.write(address, data_write, 1, 1); // no stop
00113     i2c.read(address, data, count, 0); 
00114     for(int ii = 0; ii < count; ii++) {
00115      dest[ii] = data[ii];
00116     }
00117 } 
00118  
00119 
00120 int32_t readBMP280Temperature()
00121 {
00122   uint8_t rawData[3];  // 20-bit pressure register data stored here
00123   readBytes(BMP280_ADDRESS, BMP280_TEMP_MSB, 3, &rawData[0]);  
00124   return (int32_t) (((int32_t) rawData[0] << 16 | (int32_t) rawData[1] << 8 | rawData[2]) >> 4);
00125 }
00126 
00127 int32_t readBMP280Pressure()
00128 {
00129   uint8_t rawData[3];  // 20-bit pressure register data stored here
00130   readBytes(BMP280_ADDRESS, BMP280_PRESS_MSB, 3, &rawData[0]);  
00131   return (int32_t) (((int32_t) rawData[0] << 16 | (int32_t) rawData[1] << 8 | rawData[2]) >> 4);
00132 }
00133 
00134 void BMP280Init()
00135 {
00136   // Configure the BMP280
00137   // Set T and P oversampling rates and sensor mode
00138   writeByte(BMP280_ADDRESS, BMP280_CTRL_MEAS, Tosr << 5 | Posr << 2 | Mode);
00139   // Set standby time interval in normal mode and bandwidth
00140   writeByte(BMP280_ADDRESS, BMP280_CONFIG, SBy << 5 | IIRFilter << 2);
00141   // Read and store calibration data
00142   uint8_t calib[24];
00143   readBytes(BMP280_ADDRESS, BMP280_CALIB00, 24, &calib[0]);
00144   dig_T1 = (uint16_t)(((uint16_t) calib[1] << 8) | calib[0]);
00145   dig_T2 = ( int16_t)((( int16_t) calib[3] << 8) | calib[2]);
00146   dig_T3 = ( int16_t)((( int16_t) calib[5] << 8) | calib[4]);
00147   dig_P1 = (uint16_t)(((uint16_t) calib[7] << 8) | calib[6]);
00148   dig_P2 = ( int16_t)((( int16_t) calib[9] << 8) | calib[8]);
00149   dig_P3 = ( int16_t)((( int16_t) calib[11] << 8) | calib[10]);
00150   dig_P4 = ( int16_t)((( int16_t) calib[13] << 8) | calib[12]);
00151   dig_P5 = ( int16_t)((( int16_t) calib[15] << 8) | calib[14]);
00152   dig_P6 = ( int16_t)((( int16_t) calib[17] << 8) | calib[16]);
00153   dig_P7 = ( int16_t)((( int16_t) calib[19] << 8) | calib[18]);
00154   dig_P8 = ( int16_t)((( int16_t) calib[21] << 8) | calib[20]);
00155   dig_P9 = ( int16_t)((( int16_t) calib[23] << 8) | calib[22]);
00156 }
00157 
00158 // Returns temperature in DegC, resolution is 0.01 DegC. Output value of
00159 // “5123” equals 51.23 DegC.
00160 int32_t bmp280_compensate_T(int32_t adc_T)
00161 {
00162   int32_t var1, var2, T;
00163   var1 = ((((adc_T >> 3) - ((int32_t)dig_T1 << 1))) * ((int32_t)dig_T2)) >> 11;
00164   var2 = (((((adc_T >> 4) - ((int32_t)dig_T1)) * ((adc_T >> 4) - ((int32_t)dig_T1))) >> 12) * ((int32_t)dig_T3)) >> 14;
00165   t_fine = var1 + var2;
00166   T = (t_fine * 5 + 128) >> 8;
00167   return T;
00168 }
00169 
00170 // Returns pressure in Pa as unsigned 32 bit integer in Q24.8 format (24 integer bits and 8
00171 //fractional bits).
00172 //Output value of “24674867” represents 24674867/256 = 96386.2 Pa = 963.862 hPa
00173 uint32_t bmp280_compensate_P(int32_t adc_P)
00174 {
00175   long long var1, var2, p;
00176   var1 = ((long long)t_fine) - 128000;
00177   var2 = var1 * var1 * (long long)dig_P6;
00178   var2 = var2 + ((var1*(long long)dig_P5)<<17);
00179   var2 = var2 + (((long long)dig_P4)<<35);
00180   var1 = ((var1 * var1 * (long long)dig_P3)>>8) + ((var1 * (long long)dig_P2)<<12);
00181   var1 = (((((long long)1)<<47)+var1))*((long long)dig_P1)>>33;
00182   if(var1 == 0)
00183   {
00184     return 0;
00185     // avoid exception caused by division by zero
00186   }
00187   p = 1048576 - adc_P;
00188   p = (((p<<31) - var2)*3125)/var1;
00189   var1 = (((long long)dig_P9) * (p>>13) * (p>>13)) >> 25;
00190   var2 = (((long long)dig_P8) * p)>> 19;
00191   p = ((p + var1 + var2) >> 8) + (((long long)dig_P7)<<4);
00192   return (uint32_t)p;
00193 }
00194 
00195 
00196  
00197  
00198   };
00199 #endif