File content as of revision 5:691e06db489f:

/**
 *  BME280 Combined humidity and pressure sensor library
 *
 *  @author  Toyomasa Watarai
 *  @version 1.0
 *  @date    06-April-2015
 *
 *  29 November 2016 
 *  Toyomasa Watarai code Modified  by jon trinder jont@ninelocks.com 
 *  readtemperature routine replaced
 *
 *  Library for "BME280 temperature, humidity and pressure sensor module" from Switch Science
 *    https://www.switch-science.com/catalog/2236/
 *
 *  For more information about the BME280:
 *    http://ae-bst.resource.bosch.com/media/products/dokumente/bme280/BST-BME280_DS001-10.pdf
 */

#include "mbed.h"
#include "BME280.h"

BME280::BME280(PinName sda, PinName scl, char slave_adr)
    :
    i2c_p(new I2C(sda, scl)), 
    i2c(*i2c_p),
    address(slave_adr),
    t_fine(0)
{
    initialize();
}

BME280::BME280(I2C &i2c_obj, char slave_adr)
    :
    i2c_p(NULL), 
    i2c(i2c_obj),
    address(slave_adr),
    t_fine(0)
{
    initialize();
}

BME280::~BME280()
{
    if (NULL != i2c_p)
        delete  i2c_p;
}
    
void BME280::initialize()
{
    char cmd[18];
 
    cmd[0] = 0xf2; // ctrl_hum
    cmd[1] = 0x01; // Humidity oversampling x1
    i2c.write(address, cmd, 2);
 
    cmd[0] = 0xf4; // ctrl_meas
    cmd[1] = 0x27; // Temparature oversampling x1, Pressure oversampling x1, Normal mode
    i2c.write(address, cmd, 2);
 
    cmd[0] = 0xf5; // config
    cmd[1] = 0xa0; // Standby 1000ms, Filter off
    i2c.write(address, cmd, 2);
 
    cmd[0] = 0x88; // read dig_T regs
    i2c.write(address, cmd, 1);
    i2c.read(address, cmd, 6);
 
    dig_T1 = (cmd[1] << 8) | cmd[0];
    dig_T2 = (cmd[3] << 8) | cmd[2];
    dig_T3 = (cmd[5] << 8) | cmd[4];
 
    DEBUG_PRINT("dig_T = 0x%x, 0x%x, 0x%x\n", dig_T1, dig_T2, dig_T3);
 
    cmd[0] = 0x8E; // read dig_P regs
    i2c.write(address, cmd, 1);
    i2c.read(address, cmd, 18);
 
    dig_P1 = (cmd[ 1] << 8) | cmd[ 0];
    dig_P2 = (cmd[ 3] << 8) | cmd[ 2];
    dig_P3 = (cmd[ 5] << 8) | cmd[ 4];
    dig_P4 = (cmd[ 7] << 8) | cmd[ 6];
    dig_P5 = (cmd[ 9] << 8) | cmd[ 8];
    dig_P6 = (cmd[11] << 8) | cmd[10];
    dig_P7 = (cmd[13] << 8) | cmd[12];
    dig_P8 = (cmd[15] << 8) | cmd[14];
    dig_P9 = (cmd[17] << 8) | cmd[16];
 
    DEBUG_PRINT("dig_P = 0x%x, 0x%x, 0x%x, 0x%x, 0x%x, 0x%x, 0x%x, 0x%x, 0x%x\n", dig_P1, dig_P2, dig_P3, dig_P4, dig_P5, dig_P6, dig_P7, dig_P8, dig_P9);
 
    cmd[0] = 0xA1; // read dig_H regs
    i2c.write(address, cmd, 1);
    i2c.read(address, cmd, 1);
     cmd[1] = 0xE1; // read dig_H regs
    i2c.write(address, &cmd[1], 1);
    i2c.read(address, &cmd[1], 7);

    dig_H1 = cmd[0];
    dig_H2 = (cmd[2] << 8) | cmd[1];
    dig_H3 = cmd[3];
    dig_H4 = (cmd[4] << 4) | (cmd[5] & 0x0f);
    dig_H5 = (cmd[6] << 4) | ((cmd[5]>>4) & 0x0f);
    dig_H6 = cmd[7];
 
    DEBUG_PRINT("dig_H = 0x%x, 0x%x, 0x%x, 0x%x, 0x%x, 0x%x\n", dig_H1, dig_H2, dig_H3, dig_H4, dig_H5, dig_H6);
}
 
 
 /* 
As Thomas routine was giving me weird values I rewrote it to look mostly like the adafruit 
arduino code, which in turn is a lot like the bosch datasheet 
jon Trinder
*/
 /*
float BME280::getTemperature()
{
    uint32_t temp_raw;
    float tempf;
    char cmd[4];
 
    cmd[0] = 0xfa; // temp_msb
    i2c.write(address, cmd, 1);
    i2c.read(address, &cmd[1], 3);
 
    temp_raw = (cmd[1] << 12) | (cmd[2] << 4) | (cmd[3] >> 4);
 
    int32_t temp;
 
    temp =
        (((((temp_raw >> 3) - (dig_T1 << 1))) * dig_T2) >> 11) +
        ((((((temp_raw >> 4) - dig_T1) * ((temp_raw >> 4) - dig_T1)) >> 12) * dig_T3) >> 14);
 
    t_fine = temp;
    temp = (temp * 5 + 128) >> 8;
    tempf = (float)temp;
 
    return (tempf/100.0f);
}
*/

// new version of getTemperature jont@ninelocks.com November 2016 
float BME280::getTemperature()
{
    int32_t var1, var2, T;
    int32_t adc_T;
    float temp_as_float;
    char cmd[4];
    cmd[0] = 0xfa; // temp_msb
    i2c.write(address, cmd, 1);
    i2c.read(address, &cmd[1], 3);

    //jons slow painful shifting of bits to make it readable
    adc_T = cmd[1];
    adc_T <<= 8;
    adc_T |= cmd[2];
    adc_T <<= 8;
    adc_T |= cmd[3];
     
    //from here more or less same as ada and bosch
 
    adc_T >>= 4;
    
    var1  = ((((adc_T>>3) - ((int32_t)dig_T1 <<1))) *
       ((int32_t)dig_T2)) >> 11;
    
    var2  = (((((adc_T>>4) - ((int32_t)dig_T1)) *
         ((adc_T>>4) - ((int32_t)dig_T1))) >> 12) *
       ((int32_t)dig_T3)) >> 14;
    
    t_fine = var1 + var2;
    
    T  = (t_fine * 5 + 128) >> 8;
    temp_as_float = T/100.0;
    return temp_as_float;   
}


 
float BME280::getPressure()
{
    uint32_t press_raw;
    float pressf;
    char cmd[4];
 
    cmd[0] = 0xf7; // press_msb
    i2c.write(address, cmd, 1);
    i2c.read(address, &cmd[1], 3);
 
    press_raw = (cmd[1] << 12) | (cmd[2] << 4) | (cmd[3] >> 4);
 
    int32_t var1, var2;
    uint32_t press;
 
    var1 = (t_fine >> 1) - 64000;
    var2 = (((var1 >> 2) * (var1 >> 2)) >> 11) * dig_P6;
    var2 = var2 + ((var1 * dig_P5) << 1);
    var2 = (var2 >> 2) + (dig_P4 << 16);
    var1 = (((dig_P3 * (((var1 >> 2)*(var1 >> 2)) >> 13)) >> 3) + ((dig_P2 * var1) >> 1)) >> 18;
    var1 = ((32768 + var1) * dig_P1) >> 15;
    if (var1 == 0) {
        return 0;
    }
    press = (((1048576 - press_raw) - (var2 >> 12))) * 3125;
    if(press < 0x80000000) {
        press = (press << 1) / var1;
    } else {
        press = (press / var1) * 2;
    }
    var1 = ((int32_t)dig_P9 * ((int32_t)(((press >> 3) * (press >> 3)) >> 13))) >> 12;
    var2 = (((int32_t)(press >> 2)) * (int32_t)dig_P8) >> 13;
    press = (press + ((var1 + var2 + dig_P7) >> 4));
 
    pressf = (float)press;
    return (pressf/100.0f);
}
 
float BME280::getHumidity()
{
    uint32_t hum_raw;
    float humf;
    char cmd[4];
 
    cmd[0] = 0xfd; // hum_msb
    i2c.write(address, cmd, 1);
    i2c.read(address, &cmd[1], 2);
 
    hum_raw = (cmd[1] << 8) | cmd[2];
 
    int32_t v_x1;
 
    v_x1 = t_fine - 76800;
    v_x1 =  (((((hum_raw << 14) -(((int32_t)dig_H4) << 20) - (((int32_t)dig_H5) * v_x1)) +
               ((int32_t)16384)) >> 15) * (((((((v_x1 * (int32_t)dig_H6) >> 10) *
                                            (((v_x1 * ((int32_t)dig_H3)) >> 11) + 32768)) >> 10) + 2097152) *
                                            (int32_t)dig_H2 + 8192) >> 14));
    v_x1 = (v_x1 - (((((v_x1 >> 15) * (v_x1 >> 15)) >> 7) * (int32_t)dig_H1) >> 4));
    v_x1 = (v_x1 < 0 ? 0 : v_x1);
    v_x1 = (v_x1 > 419430400 ? 419430400 : v_x1);
 
    humf = (float)(v_x1 >> 12);
 
    return (humf/1024.0f);
}