BMP280.cpp

00001 /**
00002  *  BMP280 Combined humidity and pressure sensor library
00003  *
00004  *  @author  Toyomasa Watarai
00005  *  @version 1.0
00006  *  @date    06-April-2015
00007  *
00008  *  Library for "BMP280 temperature, humidity and pressure sensor module" from Switch Science
00009  *    https://www.switch-science.com/catalog/2236/
00010  *
00011  *  For more information about the BMP280:
00012  *    http://ae-bst.resource.bosch.com/media/products/dokumente/BMP280/BST-BMP280_DS001-10.pdf
00013  */
00014 
00015 #include "mbed.h"
00016 #include "BMP280.h"
00017 
00018 BMP280::BMP280(PinName sda, PinName scl, char slave_adr)
00019     :
00020     i2c_p(new I2C(sda, scl)), 
00021     i2c(*i2c_p),
00022     address(slave_adr),
00023     t_fine(0)
00024 {
00025     initialize();
00026 }
00027 
00028 BMP280::BMP280(I2C &i2c_obj, char slave_adr)
00029     :
00030     i2c_p(NULL), 
00031     i2c(i2c_obj),
00032     address(slave_adr),
00033     t_fine(0)
00034 {
00035     initialize();
00036 }
00037 
00038 BMP280::~BMP280()
00039 {
00040     if (NULL != i2c_p)
00041         delete  i2c_p;
00042 }
00043     
00044 void BMP280::initialize()
00045 {
00046     char cmd[18];
00047  
00048     cmd[0] = 0xf2; // ctrl_hum
00049     cmd[1] = 0x01; // Humidity oversampling x1
00050     i2c.write(address, cmd, 2);
00051  
00052     cmd[0] = 0xf4; // ctrl_meas
00053     cmd[1] = 0x27; // Temparature oversampling x1, Pressure oversampling x1, Normal mode
00054     i2c.write(address, cmd, 2);
00055  
00056     cmd[0] = 0xf5; // config
00057     cmd[1] = 0xa0; // Standby 1000ms, Filter off
00058     i2c.write(address, cmd, 2);
00059  
00060     cmd[0] = 0x88; // read dig_T regs
00061     i2c.write(address, cmd, 1);
00062     i2c.read(address, cmd, 6);
00063  
00064     dig_T1 = (cmd[1] << 8) | cmd[0];
00065     dig_T2 = (cmd[3] << 8) | cmd[2];
00066     dig_T3 = (cmd[5] << 8) | cmd[4];
00067  
00068     DEBUG_PRINT("dig_T = 0x%x, 0x%x, 0x%x\n", dig_T1, dig_T2, dig_T3);
00069  
00070     cmd[0] = 0x8E; // read dig_P regs
00071     i2c.write(address, cmd, 1);
00072     i2c.read(address, cmd, 18);
00073  
00074     dig_P1 = (cmd[ 1] << 8) | cmd[ 0];
00075     dig_P2 = (cmd[ 3] << 8) | cmd[ 2];
00076     dig_P3 = (cmd[ 5] << 8) | cmd[ 4];
00077     dig_P4 = (cmd[ 7] << 8) | cmd[ 6];
00078     dig_P5 = (cmd[ 9] << 8) | cmd[ 8];
00079     dig_P6 = (cmd[11] << 8) | cmd[10];
00080     dig_P7 = (cmd[13] << 8) | cmd[12];
00081     dig_P8 = (cmd[15] << 8) | cmd[14];
00082     dig_P9 = (cmd[17] << 8) | cmd[16];
00083  
00084     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);
00085  
00086   /*  cmd[0] = 0xA1; // read dig_H regs
00087     i2c.write(address, cmd, 1);
00088     i2c.read(address, cmd, 1);
00089      cmd[1] = 0xE1; // read dig_H regs
00090     i2c.write(address, &cmd[1], 1);
00091     i2c.read(address, &cmd[1], 7);
00092 
00093     dig_H1 = cmd[0];
00094     dig_H2 = (cmd[2] << 8) | cmd[1];
00095     dig_H3 = cmd[3];
00096     dig_H4 = (cmd[4] << 4) | (cmd[5] & 0x0f);
00097     dig_H5 = (cmd[6] << 4) | ((cmd[5]>>4) & 0x0f);
00098     dig_H6 = cmd[7];
00099  
00100     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);
00101 */
00102 }
00103  
00104 float BMP280::getTemperature()
00105 {
00106     uint32_t temp_raw;
00107     float tempf;
00108     char cmd[4];
00109  
00110     cmd[0] = 0xfa; // temp_msb
00111     i2c.write(address, cmd, 1);
00112     i2c.read(address, &cmd[1], 3);
00113  
00114     temp_raw = (cmd[1] << 12) | (cmd[2] << 4) | (cmd[3] >> 4);
00115  
00116     int32_t temp;
00117  
00118     temp =
00119         (((((temp_raw >> 3) - (dig_T1 << 1))) * dig_T2) >> 11) +
00120         ((((((temp_raw >> 4) - dig_T1) * ((temp_raw >> 4) - dig_T1)) >> 12) * dig_T3) >> 14);
00121  
00122     t_fine = temp;
00123     temp = (temp * 5 + 128) >> 8;
00124     tempf = (float)temp;
00125  
00126     return (tempf/100.0f);
00127 }
00128  
00129 float BMP280::getPressure()
00130 {
00131     uint32_t press_raw;
00132     float pressf;
00133     char cmd[4];
00134  
00135     cmd[0] = 0xf7; // press_msb
00136     i2c.write(address, cmd, 1);
00137     i2c.read(address, &cmd[1], 3);
00138  
00139     press_raw = (cmd[1] << 12) | (cmd[2] << 4) | (cmd[3] >> 4);
00140  
00141     int32_t var1, var2;
00142     uint32_t press;
00143  
00144     var1 = (t_fine >> 1) - 64000;
00145     var2 = (((var1 >> 2) * (var1 >> 2)) >> 11) * dig_P6;
00146     var2 = var2 + ((var1 * dig_P5) << 1);
00147     var2 = (var2 >> 2) + (dig_P4 << 16);
00148     var1 = (((dig_P3 * (((var1 >> 2)*(var1 >> 2)) >> 13)) >> 3) + ((dig_P2 * var1) >> 1)) >> 18;
00149     var1 = ((32768 + var1) * dig_P1) >> 15;
00150     if (var1 == 0) {
00151         return 0;
00152     }
00153     press = (((1048576 - press_raw) - (var2 >> 12))) * 3125;
00154     if(press < 0x80000000) {
00155         press = (press << 1) / var1;
00156     } else {
00157         press = (press / var1) * 2;
00158     }
00159     var1 = ((int32_t)dig_P9 * ((int32_t)(((press >> 3) * (press >> 3)) >> 13))) >> 12;
00160     var2 = (((int32_t)(press >> 2)) * (int32_t)dig_P8) >> 13;
00161     press = (press + ((var1 + var2 + dig_P7) >> 4));
00162  
00163     pressf = (float)press;
00164     return (pressf/100.0f);
00165 }