BME280.cpp

00001 #include "BME280.h"
00002 
00003 BME280::BME280(I2C& bme280_i2c, uint8_t bme280_addr):
00004     _i2c(bme280_i2c), _addr(bme280_addr<<1)
00005 {
00006     _init=false;
00007 }
00008 
00009 bool BME280::init(void)
00010 {
00011     char cmd[18];
00012  
00013     cmd[0] = BME280_CTRL_HUM;
00014     cmd[1] = BME280_SAMPLING_X1;
00015     if(_i2c.write(_addr, cmd, 2)!=0)
00016         return false;
00017     
00018     cmd[0] = BME280_CTRL_MEAS; // ctrl_meas
00019     cmd[1] = 0x27; // Temparature oversampling x1, Pressure oversampling x1, Normal mode
00020     _i2c.write(_addr, cmd, 2);
00021  
00022     cmd[0] = 0xf5; // config
00023     cmd[1] = 0xa0; // Standby 1000ms, Filter off
00024     _i2c.write(_addr, cmd, 2);
00025  
00026     cmd[0] = 0x88; // read dig_T regs
00027     _i2c.write(_addr, cmd, 1);
00028     _i2c.read(_addr, cmd, 6);
00029  
00030     dig_T1 = (cmd[1] << 8) | cmd[0];
00031     dig_T2 = (cmd[3] << 8) | cmd[2];
00032     dig_T3 = (cmd[5] << 8) | cmd[4];
00033  
00034     cmd[0] = 0x8E; // read dig_P regs
00035     _i2c.write(_addr, cmd, 1);
00036     _i2c.read(_addr, cmd, 18);
00037  
00038     dig_P1 = (cmd[ 1] << 8) | cmd[ 0];
00039     dig_P2 = (cmd[ 3] << 8) | cmd[ 2];
00040     dig_P3 = (cmd[ 5] << 8) | cmd[ 4];
00041     dig_P4 = (cmd[ 7] << 8) | cmd[ 6];
00042     dig_P5 = (cmd[ 9] << 8) | cmd[ 8];
00043     dig_P6 = (cmd[11] << 8) | cmd[10];
00044     dig_P7 = (cmd[13] << 8) | cmd[12];
00045     dig_P8 = (cmd[15] << 8) | cmd[14];
00046     dig_P9 = (cmd[17] << 8) | cmd[16];
00047     
00048     cmd[0] = 0xA1; // read dig_H regs
00049     _i2c.write(_addr, cmd, 1);
00050     _i2c.read(_addr, cmd, 1);
00051      cmd[1] = 0xE1; // read dig_H regs
00052     _i2c.write(_addr, &cmd[1], 1);
00053     _i2c.read(_addr, &cmd[1], 7);
00054 
00055     dig_H1 = cmd[0];
00056     dig_H2 = (cmd[2] << 8) | cmd[1];
00057     dig_H3 = cmd[3];
00058     dig_H4 = (cmd[4] << 4) | (cmd[5] & 0x0f);
00059     dig_H5 = (cmd[6] << 4) | ((cmd[5]>>4) & 0x0f);
00060     dig_H6 = cmd[7];
00061     return true;
00062 }
00063 
00064 float BME280::getTemperature(void)
00065 {
00066     uint32_t temp_raw;
00067     float tempf;
00068     char cmd[4];
00069  
00070     cmd[0] = 0xfa; // temp_msb
00071     _i2c.write(_addr, cmd, 1);
00072     _i2c.read(_addr, &cmd[1], 3);
00073  
00074     temp_raw = (cmd[1] << 12) | (cmd[2] << 4) | (cmd[3] >> 4);
00075  
00076     int32_t temp;
00077  
00078     temp =
00079         (((((temp_raw >> 3) - (dig_T1 << 1))) * dig_T2) >> 11) +
00080         ((((((temp_raw >> 4) - dig_T1) * ((temp_raw >> 4) - dig_T1)) >> 12) * dig_T3) >> 14);
00081  
00082     t_fine = temp;
00083     temp = (temp * 5 + 128) >> 8;
00084     tempf = (float)temp;
00085  
00086     return (tempf/100.0f);
00087 }
00088  
00089 float BME280::getPressure(void)
00090 {
00091     uint32_t press_raw;
00092     float pressf;
00093     char cmd[4];
00094  
00095     cmd[0] = 0xf7; // press_msb
00096     _i2c.write(_addr, cmd, 1);
00097     _i2c.read(_addr, &cmd[1], 3);
00098  
00099     press_raw = (cmd[1] << 12) | (cmd[2] << 4) | (cmd[3] >> 4);
00100  
00101     int32_t var1, var2;
00102     uint32_t press;
00103  
00104     var1 = (t_fine >> 1) - 64000;
00105     var2 = (((var1 >> 2) * (var1 >> 2)) >> 11) * dig_P6;
00106     var2 = var2 + ((var1 * dig_P5) << 1);
00107     var2 = (var2 >> 2) + (dig_P4 << 16);
00108     var1 = (((dig_P3 * (((var1 >> 2)*(var1 >> 2)) >> 13)) >> 3) + ((dig_P2 * var1) >> 1)) >> 18;
00109     var1 = ((32768 + var1) * dig_P1) >> 15;
00110     if (var1 == 0) {
00111         return 0;
00112     }
00113     press = (((1048576 - press_raw) - (var2 >> 12))) * 3125;
00114     if(press < 0x80000000) {
00115         press = (press << 1) / var1;
00116     } else {
00117         press = (press / var1) * 2;
00118     }
00119     var1 = ((int32_t)dig_P9 * ((int32_t)(((press >> 3) * (press >> 3)) >> 13))) >> 12;
00120     var2 = (((int32_t)(press >> 2)) * (int32_t)dig_P8) >> 13;
00121     press = (press + ((var1 + var2 + dig_P7) >> 4));
00122  
00123     pressf = (float)press;
00124     return (pressf/100.0f);
00125 }
00126  
00127 float BME280::getHumidity(void)
00128 {
00129     uint32_t hum_raw;
00130     float humf;
00131     char cmd[4];
00132  
00133     cmd[0] = 0xfd; // hum_msb
00134     _i2c.write(_addr, cmd, 1);
00135     _i2c.read(_addr, &cmd[1], 2);
00136  
00137     hum_raw = (cmd[1] << 8) | cmd[2];
00138  
00139     int32_t v_x1;
00140  
00141     v_x1 = t_fine - 76800;
00142     v_x1 =  (((((hum_raw << 14) -(((int32_t)dig_H4) << 20) - (((int32_t)dig_H5) * v_x1)) +
00143                ((int32_t)16384)) >> 15) * (((((((v_x1 * (int32_t)dig_H6) >> 10) *
00144                                             (((v_x1 * ((int32_t)dig_H3)) >> 11) + 32768)) >> 10) + 2097152) *
00145                                             (int32_t)dig_H2 + 8192) >> 14));
00146     v_x1 = (v_x1 - (((((v_x1 >> 15) * (v_x1 >> 15)) >> 7) * (int32_t)dig_H1) >> 4));
00147     v_x1 = (v_x1 < 0 ? 0 : v_x1);
00148     v_x1 = (v_x1 > 419430400 ? 419430400 : v_x1);
00149  
00150     humf = (float)(v_x1 >> 12);
00151  
00152     return (humf/1024.0f);
00153 }