A library to read BME280 sensor with error detection
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BME280.cpp
00001 /** 00002 * BME280 Combined humidity and pressure sensor library 00003 * 00004 * @author Toyomasa Watarai 00005 * @version 1.0 00006 * @date 06-April-2015 00007 * 00008 * Library for "BME280 temperature, humidity and pressure sensor module" from Switch Science 00009 * https://www.switch-science.com/catalog/2236/ 00010 * 00011 * For more information about the BME280: 00012 * http://ae-bst.resource.bosch.com/media/products/dokumente/bme280/BST-BME280_DS001-10.pdf 00013 */ 00014 00015 #include "mbed.h" 00016 #include "BME280.h" 00017 00018 BME280::BME280(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 i2c.frequency(10000); 00027 } 00028 00029 BME280::BME280(I2C &i2c_obj, char slave_adr) 00030 : 00031 i2c_p(NULL), 00032 i2c(i2c_obj), 00033 address(slave_adr), 00034 t_fine(0) 00035 { 00036 initialize(); 00037 } 00038 00039 BME280::~BME280() 00040 { 00041 if (NULL != i2c_p) 00042 delete i2c_p; 00043 } 00044 00045 void BME280::initialize() 00046 { 00047 char cmd[18]; 00048 00049 cmd[0] = 0xf2; // ctrl_hum 00050 cmd[1] = 0x01; // Humidity oversampling x1 00051 i2c.write(address, cmd, 2); 00052 00053 cmd[0] = 0xf4; // ctrl_meas 00054 cmd[1] = 0x27; // Temparature oversampling x1, Pressure oversampling x1, Normal mode 00055 i2c.write(address, cmd, 2); 00056 00057 cmd[0] = 0xf5; // config 00058 cmd[1] = 0xa0; // Standby 1000ms, Filter off 00059 i2c.write(address, cmd, 2); 00060 00061 cmd[0] = 0x88; // read dig_T regs 00062 i2c.write(address, cmd, 1); 00063 i2c.read(address, cmd, 6); 00064 00065 dig_T1 = (cmd[1] << 8) | cmd[0]; 00066 dig_T2 = (cmd[3] << 8) | cmd[2]; 00067 dig_T3 = (cmd[5] << 8) | cmd[4]; 00068 00069 DEBUG_PRINT("dig_T = 0x%x, 0x%x, 0x%x\n", dig_T1, dig_T2, dig_T3); 00070 00071 cmd[0] = 0x8E; // read dig_P regs 00072 i2c.write(address, cmd, 1); 00073 i2c.read(address, cmd, 18); 00074 00075 dig_P1 = (cmd[ 1] << 8) | cmd[ 0]; 00076 dig_P2 = (cmd[ 3] << 8) | cmd[ 2]; 00077 dig_P3 = (cmd[ 5] << 8) | cmd[ 4]; 00078 dig_P4 = (cmd[ 7] << 8) | cmd[ 6]; 00079 dig_P5 = (cmd[ 9] << 8) | cmd[ 8]; 00080 dig_P6 = (cmd[11] << 8) | cmd[10]; 00081 dig_P7 = (cmd[13] << 8) | cmd[12]; 00082 dig_P8 = (cmd[15] << 8) | cmd[14]; 00083 dig_P9 = (cmd[17] << 8) | cmd[16]; 00084 00085 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); 00086 00087 cmd[0] = 0xA1; // read dig_H regs 00088 i2c.write(address, cmd, 1); 00089 i2c.read(address, cmd, 1); 00090 cmd[1] = 0xE1; // read dig_H regs 00091 i2c.write(address, &cmd[1], 1); 00092 i2c.read(address, &cmd[1], 7); 00093 00094 dig_H1 = cmd[0]; 00095 dig_H2 = (cmd[2] << 8) | cmd[1]; 00096 dig_H3 = cmd[3]; 00097 dig_H4 = (cmd[4] << 4) | (cmd[5] & 0x0f); 00098 dig_H5 = (cmd[6] << 4) | ((cmd[5]>>4) & 0x0f); 00099 dig_H6 = cmd[7]; 00100 00101 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); 00102 } 00103 00104 float BME280::getTemperature() 00105 { 00106 uint32_t temp_raw; 00107 float tempf; 00108 char cmd[4]; 00109 00110 cmd[0] = 0xfa; // temp_msb 00111 int writeResult = i2c.write(address, cmd, 1); 00112 int readResult = i2c.read(address, &cmd[1], 3); 00113 00114 if(writeResult != 0 || readResult != 0) 00115 return -10000000; 00116 00117 temp_raw = (cmd[1] << 12) | (cmd[2] << 4) | (cmd[3] >> 4); 00118 00119 int32_t temp; 00120 00121 temp = 00122 (((((temp_raw >> 3) - (dig_T1 << 1))) * dig_T2) >> 11) + 00123 ((((((temp_raw >> 4) - dig_T1) * ((temp_raw >> 4) - dig_T1)) >> 12) * dig_T3) >> 14); 00124 00125 t_fine = temp; 00126 temp = (temp * 5 + 128) >> 8; 00127 tempf = (float)temp; 00128 00129 return (tempf/100.0f); 00130 } 00131 00132 float BME280::getPressure() 00133 { 00134 uint32_t press_raw; 00135 float pressf; 00136 char cmd[4]; 00137 00138 cmd[0] = 0xf7; // press_msb 00139 int writeResult = i2c.write(address, cmd, 1); 00140 int readResult = i2c.read(address, &cmd[1], 3); 00141 00142 if(writeResult != 0 || readResult != 0) 00143 return -10000000; 00144 00145 press_raw = (cmd[1] << 12) | (cmd[2] << 4) | (cmd[3] >> 4); 00146 00147 int32_t var1, var2; 00148 uint32_t press; 00149 00150 var1 = (t_fine >> 1) - 64000; 00151 var2 = (((var1 >> 2) * (var1 >> 2)) >> 11) * dig_P6; 00152 var2 = var2 + ((var1 * dig_P5) << 1); 00153 var2 = (var2 >> 2) + (dig_P4 << 16); 00154 var1 = (((dig_P3 * (((var1 >> 2)*(var1 >> 2)) >> 13)) >> 3) + ((dig_P2 * var1) >> 1)) >> 18; 00155 var1 = ((32768 + var1) * dig_P1) >> 15; 00156 if (var1 == 0) { 00157 return 0; 00158 } 00159 press = (((1048576 - press_raw) - (var2 >> 12))) * 3125; 00160 if(press < 0x80000000) { 00161 press = (press << 1) / var1; 00162 } else { 00163 press = (press / var1) * 2; 00164 } 00165 var1 = ((int32_t)dig_P9 * ((int32_t)(((press >> 3) * (press >> 3)) >> 13))) >> 12; 00166 var2 = (((int32_t)(press >> 2)) * (int32_t)dig_P8) >> 13; 00167 press = (press + ((var1 + var2 + dig_P7) >> 4)); 00168 00169 pressf = (float)press; 00170 return (pressf/100.0f); 00171 } 00172 00173 float BME280::getHumidity() 00174 { 00175 uint32_t hum_raw; 00176 float humf; 00177 char cmd[4]; 00178 00179 cmd[0] = 0xfd; // hum_msb 00180 int writeResult = i2c.write(address, cmd, 1); 00181 int readResult = i2c.read(address, &cmd[1], 2); 00182 00183 if(writeResult != 0 || readResult != 0) 00184 return -10000000; 00185 00186 hum_raw = (cmd[1] << 8) | cmd[2]; 00187 00188 int32_t v_x1; 00189 00190 v_x1 = t_fine - 76800; 00191 v_x1 = (((((hum_raw << 14) -(((int32_t)dig_H4) << 20) - (((int32_t)dig_H5) * v_x1)) + 00192 ((int32_t)16384)) >> 15) * (((((((v_x1 * (int32_t)dig_H6) >> 10) * 00193 (((v_x1 * ((int32_t)dig_H3)) >> 11) + 32768)) >> 10) + 2097152) * 00194 (int32_t)dig_H2 + 8192) >> 14)); 00195 v_x1 = (v_x1 - (((((v_x1 >> 15) * (v_x1 >> 15)) >> 7) * (int32_t)dig_H1) >> 4)); 00196 v_x1 = (v_x1 < 0 ? 0 : v_x1); 00197 v_x1 = (v_x1 > 419430400 ? 419430400 : v_x1); 00198 00199 humf = (float)(v_x1 >> 12); 00200 00201 return (humf/1024.0f); 00202 }
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