Merge pull request #85 from AgentZombie/temp-adjust-84

Provide temperature compensation #84

Author: ladyada

Adafruit_BME280.cpp

@@ -419,7 +419,7 @@ float Adafruit_BME280::readTemperature(void) {
           ((int32_t)_bme280_calib.dig_T3)) >>
          14;
 
-  t_fine = var1 + var2;
+  t_fine = var1 + var2 + t_fine_adjust;
 
   float T = (t_fine * 5 + 128) >> 8;
   return T / 100;
@@ -540,6 +540,24 @@ float Adafruit_BME280::seaLevelForAltitude(float altitude, float atmospheric) {
  */
 uint32_t Adafruit_BME280::sensorID(void) { return _sensorID; }
 
+/*!
+ *   Returns the current temperature compensation value in degrees Celcius
+ *   @returns the current temperature compensation value in degrees Celcius
+ */
+float Adafruit_BME280::getTemperatureCompensation(void) {
+  return float(((t_fine_adjust * 5) >> 8) / 100);
+};
+
+/*!
+ *  Sets a value to be added to each temperature reading. This adjusted
+ *  temperature is used in pressure and humidity readings.
+ *  @param  adjustment  Value to be added to each tempature reading in Celcius
+ */
+void Adafruit_BME280::setTemperatureCompensation(float adjustment) {
+  // convert the value in C into and adjustment to t_fine
+  t_fine_adjust = ((int32_t(adjustment * 100) << 8)) / 5;
+};
+
 /*!
     @brief  Gets an Adafruit Unified Sensor object for the temp sensor component
     @return Adafruit_Sensor pointer to temperature sensor

Adafruit_BME280.h

@@ -234,6 +234,9 @@ class Adafruit_BME280 {
   float seaLevelForAltitude(float altitude, float pressure);
   uint32_t sensorID(void);
 
+  float getTemperatureCompensation(void);
+  void setTemperatureCompensation(float);
+
   Adafruit_Sensor *getTemperatureSensor(void);
   Adafruit_Sensor *getPressureSensor(void);
   Adafruit_Sensor *getHumiditySensor(void);
@@ -274,6 +277,9 @@ class Adafruit_BME280 {
   int8_t _miso; //!< for the SPI interface
   int8_t _sck;  //!< for the SPI interface
 
+  int32_t t_fine_adjust = 0; //!< add to compensate temp readings and in turn
+                             //!< to pressure and humidity readings
+
   bme280_calib_data _bme280_calib; //!< here calibration data is stored
 
   /**************************************************************************/