Kevin Braun
Multi environmental sensor
My version of the bme280 pressure, humidity and temperature sensor
Diff: bme280.cpp
- Revision:
- 3:96075bee19f0
- Parent:
- 0:40b4ebf843c6
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/bme280.cpp Fri Apr 22 14:25:55 2016 +0000
@@ -0,0 +1,425 @@
+// Borch BME280 Barometer, Humidity and Temperature sensor IC
+
+#include "bme280.h"
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// Constructor, to allow for user to select i2c address based on CSB pin
+
+bme280::bme280(PinName sda, PinName scl, CSBpolarity CSBpin) : _i2c(sda, scl) {
+ _i2c.frequency(400000);
+ i2cWAddr = BME280_WADDR;
+ i2cRAddr = BME280_RADDR;
+ if(CSBpin == CSBpin_1) {
+ i2cWAddr++;
+ i2cWAddr++;
+ i2cRAddr++;
+ i2cRAddr++;
+ }
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// deconstructor
+
+bme280::~bme280() {
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// I2C start. Returns "ack" from slave
+
+int bme280::_i2c_start(uint8_t i2c_addr) {
+ int ack;
+ _i2c.start();
+ ack = _i2c_write(i2c_addr);
+ return(ack);
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// I2C stop
+
+void bme280::_i2c_stop() {
+ _i2c.stop();
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// I2C write a byte. Returns "ack" from slave
+
+uint8_t bme280::_i2c_write(uint8_t data) {
+ int ack = _i2c.write(data);
+ return(ack);
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// I2C read byte and sending ACK. Returns data byte.
+
+uint8_t bme280::_i2c_readACK() {
+ uint8_t rdata = _i2c.read(1);
+ return(rdata);
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// I2C read byte and sending NACK. Returns data byte.
+
+uint8_t bme280::_i2c_readNACK() {
+ uint8_t rdata = _i2c.read(0);
+ return(rdata);
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// Get BME280 ID register
+
+uint8_t bme280::getBmeID() {
+#if defined BMEi2cLOWLEVEL
+ _i2c_start(i2cWAddr);
+ _i2c_write(BME280_CHIP_ID_REG);
+ _i2c_start(i2cRAddr);
+ uint8_t rdata = _i2c_readNACK();
+ _i2c_stop();
+ return(rdata);
+#else
+ bme280Buffer[0] = BME280_CHIP_ID_REG;
+ _i2c.write(i2cWAddr, bme280Buffer, 1, true);
+ _i2c.read(i2cRAddr, bme280Buffer, 1, false);
+ uint8_t rdata = bme280Buffer[0];
+ return(bme280Buffer[0]);
+#endif
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// Soft reset the chip
+
+uint8_t bme280::resetBme() {
+#if defined BMEi2cLOWLEVEL
+ uint8_t rdata = _i2c_start(i2cWAddr);
+ if(rdata) return(rdata);
+ _i2c_write(BME280_RST_REG);
+ _i2c_write(BME280_RESET_VALUE);
+ _i2c_stop();
+#else
+ bme280Buffer[0] = BME280_RST_REG;
+ bme280Buffer[1] = BME280_RESET_VALUE;
+ uint8_t rdata = _i2c.write(i2cWAddr, bme280Buffer, 2, false);
+#endif
+ return(rdata);
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// Get BME280 status register. Returns register value
+
+uint8_t bme280::getBmeStatus() {
+#if defined BMEi2cLOWLEVEL
+ _i2c_start(i2cWAddr);
+ _i2c_write(BME280_STAT_REG);
+ _i2c_start(i2cRAddr);
+ uint8_t rdata = _i2c_readNACK();
+ _i2c_stop();
+ return(rdata);
+#else
+ bme280Buffer[0] = BME280_STAT_REG;
+ _i2c.write(i2cWAddr, bme280Buffer, 1, true);
+ _i2c.read(i2cRAddr, bme280Buffer, 1, false);
+ return(bme280Buffer[0]);
+#endif
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// Get BME280 PTH values. Saves raw data is data structure. Returns 0 if successful, !0 if status was busy - pass thru from getBmeStatus();
+
+uint8_t bme280::getBmeRawData(bme_data& bmed) {
+ uint8_t rdata = getBmeStatus();
+ if(rdata) return(rdata);
+ bmed.raw_hum = 0;
+#if defined BMEi2cLOWLEVEL
+ _i2c_start(i2cWAddr);
+ _i2c_write(BME280_PRESSURE_MSB_REG);
+ _i2c_start(i2cRAddr);
+
+ // MSB first LSB second XLSB third
+ bmed.raw_baro = ((_i2c_readACK() << 12) | (_i2c_readACK() << 4) | (_i2c_readACK()));
+ bmed.raw_temp = ((_i2c_readACK() << 12) | (_i2c_readACK() << 4) | (_i2c_readACK()));
+ bmed.raw_hum = ((_i2c_readACK() << 8) | (_i2c_readNACK()));
+ _i2c_stop();
+#else
+ bme280Buffer[0] = BME280_PRESSURE_MSB_REG;
+ _i2c.write(i2cWAddr, bme280Buffer, 1, true);
+ _i2c.read(i2cRAddr, bme280Buffer, 8, false);
+ // MSB first LSB second XLSB third
+ bmed.raw_baro = ((bme280Buffer[0] << 12) | (bme280Buffer[1] << 4) | (bme280Buffer[2]));
+ bmed.raw_temp = ((bme280Buffer[3] << 12) | (bme280Buffer[4] << 4) | (bme280Buffer[5]));
+ bmed.raw_hum = ((bme280Buffer[6] << 8) | (bme280Buffer[7]));
+#endif
+ return(0);
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+//Convert BME280 PTH values. Takes raw data from data structure and applies calibration values to it.
+
+void bme280::convertBmeRawData(bme_data& bmed, bme_cal& bmec) {
+
+ //Returns temperature in DegC, resolution is 0.01 DegC. Output value of “5123” equals 51.23 DegC.
+ //t_fine carries fine temperature as global value
+ int var1t = ((((bmed.raw_temp >> 3) - ((int)bmec.dig_T1 << 1))) * ((int)bmec.dig_T2)) >> 11;
+ int var2t = (((((bmed.raw_temp >> 4) - ((int)bmec.dig_T1)) * ((bmed.raw_temp >> 4) - ((int)bmec.dig_T1))) >> 12) *
+ ((int)bmec.dig_T3)) >> 14;
+ bmec.t_fine = var1t + var2t;
+ bmed.corr_temp = (bmec.t_fine * 5 + 128) >> 8;
+ bmed.bme_temp = (double)bmed.corr_temp / 100.0;
+
+ //Returns pressure in Pa as unsigned 32 bit integer in Q24.8 format (24 integer bits and 8 fractional bits).
+ //Output value of “24674867” represents 24674867/256 = 96386.2 Pa = 963.862 hPa
+ int64_t var1p, var2p, p;
+ var1p = ((int64_t)bmec.t_fine) - 128000;
+ var2p = var1p * var1p * (int64_t)bmec.dig_P6;
+ var2p = var2p + ((var1p * (int64_t)bmec.dig_P5) << 17);
+ var2p = var2p + (((int64_t)bmec.dig_P4) << 35);
+ var1p = ((var1p * var1p * (int64_t)bmec.dig_P3 )>> 8) + ((var1p * (int64_t)bmec.dig_P2) << 12);
+ var1p = (((((int64_t)1) << 47) + var1p)) * ((int64_t)bmec.dig_P1) >> 33;
+ if (var1p == 0) return; // avoid exception caused by division by zero
+ p = 1048576 - bmed.raw_baro;
+ p = (((p << 31) - var2p) * 3125)/var1p;
+ var1p = (((int64_t)bmec.dig_P9) * (p >> 13) * (p >> 13)) >> 25;
+ var2p = (((int64_t)bmec.dig_P8) * p) >> 19;
+ p = ((p + var1p + var2p) >> 8) + (((int64_t)bmec.dig_P7) << 4);
+ bmed.corr_baro = p >> 8;
+ bmed.bme_baro = (double)bmed.corr_baro / 100.0;
+
+ //Returns humidity in %RH as unsigned 32 bit integer in Q22.10 format (22 integer and 10 fractional bits).
+ //Output value of “47445” represents 47445/1024 = 46.333 %RH
+ int v_x1_u32r = (bmec.t_fine - ((int)76800));
+ v_x1_u32r = (((((bmed.raw_hum << 14) - (((int)bmec.dig_H4) << 20) - (((int)bmec.dig_H5) * v_x1_u32r)) +
+ ((int)16384)) >> 15) * (((((((v_x1_u32r * ((int)bmec.dig_H6)) >> 10) * (((v_x1_u32r *
+ ((int)bmec.dig_H3)) >> 11) + ((int)32768))) >> 10) + ((int)2097152)) *
+ ((int)bmec.dig_H2) + 8192) >> 14));
+ v_x1_u32r = (v_x1_u32r - (((((v_x1_u32r >> 15) * (v_x1_u32r >> 15)) >> 7) * ((int)bmec.dig_H1)) >> 4));
+ v_x1_u32r = (v_x1_u32r < 0 ? 0 : v_x1_u32r);
+ v_x1_u32r = (v_x1_u32r > 419430400 ? 419430400 : v_x1_u32r);
+ bmed.corr_hum = (uint32_t)(v_x1_u32r >> 12);
+ bmed.bme_hum = (double)bmed.corr_hum / 1024.0; //was: / 1000.0
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+//Convert BME280 PTH values. Takes raw data from data structure and applies calibration values to it.
+//Note: This is the floating point version.
+
+void bme280::convertBmeRawDataFloat(bme_data& bmed, bme_cal& bmec) {
+
+ //Returns temperature in DegC, double precision. Output value of “51.23” equals 51.23 DegC.
+ //t_fine carries fine temperature as global value
+ double var1, var2;
+ var1 = (((double)bmed.raw_temp) / 16384.0 - ((double)bmec.dig_T1) / 1024.0) * ((double)bmec.dig_T2);
+ var2 = ((((double)bmed.raw_temp) / 131072.0 - ((double)bmec.dig_T1) / 8192.0) *
+ (((double)bmed.raw_temp) / 131072.0 - ((double)bmec.dig_T1) / 8192.0)) * ((double)bmec.dig_T3);
+ bmec.t_fine = (int)(var1 + var2);
+ bmed.corr_temp = 0;
+ bmed.bme_temp = (var1 + var2) / 5120.0;
+
+ //Returns pressure in Pa as double. Output value of “96386.2” equals 96386.2 Pa = 963.862 hPa
+ double p;
+ var1 = ((double)bmec.t_fine / 2.0) - 64000.0;
+ var2 = var1 * var1 * ((double)bmec.dig_P6) / 32768.0;
+ var2 = var2 + var1 * ((double)bmec.dig_P5) * 2.0;
+ var2 = (var2 / 4.0)+(((double)bmec.dig_P4) * 65536.0);
+ var1 = (((double)bmec.dig_P3) * var1 * var1 / 524288.0 + ((double)bmec.dig_P2) * var1) / 524288.0;
+ var1 = (1.0 + var1 / 32768.0)*((double)bmec.dig_P1);
+ if (var1 == 0.0) {
+ bmed.corr_baro = 0;
+ bmed.bme_baro = 0.0;
+ return; //avoid exception caused by division by zero
+ }
+ p = 1048576.0 - (double)bmed.raw_baro;
+ p = (p - (var2 / 4096.0)) * 6250.0 / var1;
+ var1 = ((double)bmec.dig_P9) * p * p / 2147483648.0;
+ var2 = p * ((double)bmec.dig_P8) / 32768.0;
+ p = p + (var1 + var2 + ((double)bmec.dig_P7)) / 16.0;
+ bmed.corr_baro = 0;
+ bmed.bme_baro = p / 100.0;
+
+ //Returns humidity in %rH as as double. Output value of “46.332” represents 46.332 %rH
+ double var_H;
+ var_H = (((double)bmec.t_fine) - 76800.0);
+ var_H = (bmed.raw_hum - (((double)bmec.dig_H4) * 64.0 + ((double)bmec.dig_H5) / 16384.0 * var_H)) *
+ (((double)bmec.dig_H2) / 65536.0 * (1.0 + ((double)bmec.dig_H6) / 67108864.0 * var_H *
+ (1.0 + ((double)bmec.dig_H3) / 67108864.0 * var_H)));
+ var_H = var_H * (1.0 - ((double)bmec.dig_H1) * var_H / 524288.0);
+ if (var_H > 100.0) {
+ var_H = 100.0;
+ } else if (var_H < 0.0) {
+ var_H = 0.0;
+ }
+ bmed.corr_hum = 0;
+ bmed.bme_hum = var_H;
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// Initialize the chip
+
+uint8_t bme280::initBme(bme_cal& bmec) {
+#if defined BMEi2cLOWLEVEL
+ //initialize the chip
+ _i2c_start(i2cWAddr);
+ _i2c_write(BME280_CTRL_HUMIDITY_REG);
+ _i2c_write(BME280_CTRL_HUMIDITY_REG_DATA);
+ _i2c_stop();
+
+ _i2c_start(i2cWAddr);
+ _i2c_write(BME280_CTRL_MEAS_REG);
+ _i2c_write(BME280_CTRL_MEAS_REG_DATA);
+ _i2c_stop();
+
+ _i2c_start(i2cWAddr);
+ _i2c_write(BME280_CONFIG_REG);
+ _i2c_write(BME280_CONFIG_REG_DATA);
+ _i2c_stop();
+
+ //read back config registers
+ _i2c_start(i2cWAddr);
+ _i2c_write(BME280_CTRL_HUMIDITY_REG);
+ _i2c_start(i2cRAddr);
+ bmec.ctrl_hum_reg = _i2c_readACK();
+ uint8_t status = _i2c_readACK();
+ bmec.ctrl_meas_reg = _i2c_readACK();
+ bmec.config_reg = _i2c_readNACK();
+ _i2c_stop();
+
+ //now get the calibration registers
+ _i2c_start(i2cWAddr);
+ _i2c_write(BME280_CAL_DATA_START_1);
+ _i2c_start(i2cRAddr);
+ // LSB first MSB second
+ bmec.dig_T1 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ bmec.dig_T2 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ bmec.dig_T3 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ bmec.dig_P1 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ bmec.dig_P2 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ bmec.dig_P3 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ bmec.dig_P4 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ bmec.dig_P5 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ bmec.dig_P6 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ bmec.dig_P7 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ bmec.dig_P8 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ bmec.dig_P9 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ uint8_t rdata = (_i2c_readACK()); //dummy read of address 0xa0
+ bmec.dig_H1 = (_i2c_readNACK());
+ _i2c_stop();
+
+ //finally, get the Humid calibration registers
+ _i2c_start(i2cWAddr);
+ _i2c_write(BME280_CAL_DATA_START_2);
+ _i2c_start(i2cRAddr);
+ bmec.dig_H2 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ bmec.dig_H3 = (_i2c_readACK());
+ bmec.dig_H4 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ bmec.dig_H5 = (_i2c_readACK() + (_i2c_readACK() << 8));
+ bmec.dig_H6 = (_i2c_readNACK());
+ _i2c_stop();
+
+#else
+ //initialize the chip
+ bme280Buffer[0] = BME280_CTRL_HUMIDITY_REG;
+ bme280Buffer[1] = BME280_CTRL_HUMIDITY_REG_DATA;
+ _i2c.write(i2cWAddr, bme280Buffer, 2, false);
+
+ bme280Buffer[0] = BME280_CTRL_MEAS_REG;
+ bme280Buffer[1] = BME280_CTRL_MEAS_REG_DATA;
+ _i2c.write(i2cWAddr, bme280Buffer, 2, false);
+
+ bme280Buffer[0] = BME280_CONFIG_REG;
+ bme280Buffer[1] = BME280_CONFIG_REG_DATA;
+ _i2c.write(i2cWAddr, bme280Buffer, 2, false);
+
+ //read back config registers
+ bme280Buffer[0] = BME280_CTRL_HUMIDITY_REG;
+ _i2c.write(i2cWAddr, bme280Buffer, 1, true);
+ _i2c.read(i2cRAddr, bme280Buffer, 4, false);
+ bmec.ctrl_hum_reg = bme280Buffer[0];
+// uint8_t status = bme280Buffer[1];
+ bmec.ctrl_meas_reg = bme280Buffer[2];
+ bmec.config_reg = bme280Buffer[3];
+
+ //now get the calibration registers, Temp and Press first
+ bme280Buffer[0] = BME280_CAL_DATA_START_1;
+ _i2c.write(i2cWAddr, bme280Buffer, 1, true);
+ _i2c.read(i2cRAddr, bme280Buffer, 26, false);
+ // LSB first MSB second
+ bmec.dig_T1 = (bme280Buffer[0] | (bme280Buffer[1] << 8));
+ bmec.dig_T2 = (bme280Buffer[2] | (bme280Buffer[3] << 8));
+ bmec.dig_T3 = (bme280Buffer[4] | (bme280Buffer[5] << 8));
+ bmec.dig_P1 = (bme280Buffer[6] | (bme280Buffer[7] << 8));
+ bmec.dig_P2 = (bme280Buffer[8] | (bme280Buffer[9] << 8));
+ bmec.dig_P3 = (bme280Buffer[10] | (bme280Buffer[11] << 8));
+ bmec.dig_P4 = (bme280Buffer[12] | (bme280Buffer[13] << 8));
+ bmec.dig_P5 = (bme280Buffer[14] | (bme280Buffer[15] << 8));
+ bmec.dig_P6 = (bme280Buffer[16] | (bme280Buffer[17] << 8));
+ bmec.dig_P7 = (bme280Buffer[18] | (bme280Buffer[19] << 8));
+ bmec.dig_P8 = (bme280Buffer[20] | (bme280Buffer[21] << 8));
+ bmec.dig_P9 = (bme280Buffer[22] | (bme280Buffer[23] << 8));
+// uint8_t rdata = (bme280Buffer[24]); //dummy read of address 0xa0
+ bmec.dig_H1 = (bme280Buffer[25]);
+
+ //finally, get the Humid calibration registers
+ bme280Buffer[0] = BME280_CAL_DATA_START_2;
+ _i2c.write(i2cWAddr, bme280Buffer, 1, true);
+ _i2c.read(i2cRAddr, bme280Buffer, 8, false);
+ bmec.dig_H2 = (bme280Buffer[0] | (bme280Buffer[1] << 8));
+ bmec.dig_H3 = (bme280Buffer[2]);
+ bmec.dig_H4 = ((bme280Buffer[4] & 15) | (bme280Buffer[3] << 4));
+ bmec.dig_H5 = (((bme280Buffer[4] >> 4) & 15) | (bme280Buffer[5] << 4));
+ bmec.dig_H6 = (bme280Buffer[6]);
+
+#endif
+ return(0);
+ }
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// Return corrected altitude (in feet) from barometer at sea level (in mB)
+
+float bme280::getAltitudeFT(bme_data& bmed, float sea_pressure) {
+ return(float)((1 - (pow((bmed.bme_baro / (double)sea_pressure), 0.190284))) * 145366.45);
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// Return corrected barometer, based on altitude (in feet)
+
+float bme280::getSeaLevelBaroFT(bme_data& bmed, float known_alt) {
+ return(pow(pow((bmed.bme_baro * MB_INHG_DOUBLE), 0.190284) + 0.00001313 * (double)known_alt , 5.2553026) * INHG_MB_DOUBLE);
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// Return corrected barometer, based on altitude (in meters)
+
+float bme280::getSeaLevelBaroM(bme_data& bmed, float known_alt) {
+ return(pow(pow((bmed.bme_baro * MB_INHG_DOUBLE), 0.190284) + 0.00001313 * (double)known_alt * FEET_METERS , 5.2553026) * INHG_MB_DOUBLE);
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// Return dew point. More accurate, slower
+
+float bme280::getDewPt(bme_data& bmed) {
+ // dewPoint function NOAA
+ // reference: http://wahiduddin.net/calc/density_algorithms.htm
+ double A0= 373.15 / (273.15 + (double)bmed.bme_temp);
+ double SUM = -7.90298 * (A0 -1);
+ SUM += 5.02808 * log10(A0);
+ SUM += -1.3816e-7 * (pow(10, (11.344 * (1 - 1/A0))) -1) ;
+ SUM += 8.1328e-3 * (pow(10,(-3.49149 * (A0 -1))) -1) ;
+ SUM += log10(1013.246);
+ double VP = pow(10, SUM -3) * bmed.bme_hum;
+ double T = log(VP / 0.61078); // temp var
+ return (241.88 * T) / (17.558 - T);
+}
+
+//--------------------------------------------------------------------------------------------------------------------------------------//
+// Return dew point. Less accurate, faster
+
+float bme280::getDewPtFast(bme_data& bmed) {
+ // delta max = 0.6544 wrt dewPoint()
+ // 5x faster than dewPoint()
+ // reference: http://en.wikipedia.org/wiki/Dew_point
+ double bmeDtzA = 17.271;
+ double bmeDtzB = 237.7;
+ double bmeDtzC = (bmeDtzA * bmed.bme_temp) / (bmeDtzB + bmed.bme_temp) + log(bmed.bme_hum / 100.0);
+ double bmeDtzD = (bmeDtzB * bmeDtzC) / (bmeDtzA - bmeDtzC);
+ return (bmeDtzD);
+}
+
+
+