Added pressure related API functions

src/W800 SDK v1.00.08/app/app_drivers/i2c/BMP280.c

@@ -139,6 +139,52 @@ float BMP280_get_temperature(void)
     return T / 100;
 }
 
+float BMP280_get_pressure(float * const temperature)
+{
+    int64_t var1, var2, p;
+    uint8_t data[3];
+
+    float temp = BMP280_get_temperature();
+    if(temperature) *temperature = temp;
+    
+    if(!i2c_read(BMP280_I2C_ADDR, BMP280_PRESS_MSB, data, sizeof data)) return 0.0f;
+
+    int32_t adc_P = data[0] << 16 | data[1] << 8 | data[2];
+
+    var1 = ((int64_t)t_fine) - 128000;
+    var2 = var1 * var1 * (int64_t)_calibration_data.dig_P6;
+    var2 = var2 + ((var1*(int64_t)_calibration_data.dig_P5)<<17);
+    var2 = var2 + (((int64_t)_calibration_data.dig_P4)<<35);
+    var1 = ((var1 * var1 * (int64_t)_calibration_data.dig_P3)>>8) + ((var1 * (int64_t)_calibration_data.dig_P2)<<12);
+    var1 = (((((int64_t)1)<<47)+var1))*((int64_t)_calibration_data.dig_P1)>>33;
+    
+    if (var1 == 0)
+    {
+        return 0.0f; // avoid exception caused by division by zero
+    }
+
+    p = 1048576-adc_P;
+    p = (((p<<31)-var2)*3125)/var1;
+    var1 = (((int64_t)_calibration_data.dig_P9) * (p>>13) * (p>>13)) >> 25;
+    var2 = (((int64_t)_calibration_data.dig_P8) * p) >> 19;
+    p = ((p + var1 + var2) >> 8) + (((int64_t)_calibration_data.dig_P7)<<4);
+    
+    return (float)p/256; //to get rid of the Q24.8 format ! 
+}
+
+float BMP280_get_altitude(float pressureAtSeeLevel, float * const pressure, float * const temperature)
+{
+    if(pressureAtSeeLevel == 0) pressureAtSeeLevel = 1013.25;
+
+    float press = BMP280_get_pressure(temperature);
+
+    if(pressure) *pressure = press;
+
+    press /= 100;
+
+    return 44330 * (1.0 - pow(press / pressureAtSeeLevel, 0.1903));
+}
+
 bool BMP280_software_reset(void)
 {
     return i2c_write_reg(BMP280_I2C_ADDR, BMP280_RESET, BMP280_RESET_CODE);

src/W800 SDK v1.00.08/app/app_drivers/i2c/BMP280.h

@@ -77,16 +77,70 @@ typedef enum BMP280_Standby_Duration
     BMP280_Standby_4000MS = 7,
 } BMP280_Standby_Duration_e;
 
+/**
+ * @brief Initializes the BMP280 sensor. This must be called before any other API functions.
+ * Don't forget to initialize the I2C peripheral using the i2c_init function first !
+ * 
+ * @return true on success
+ * @return false on failure
+ */
 bool BMP280_init(void);
 
+/**
+ * @brief Configures the sensor by setting the sensor operating mode, temperature oversampling, pressure oversampling, the filter and the standby duration.
+ * 
+ * @param mode the operating mode, can be BMP280_Sleep, BMP280_Forced or BMP280_Normal.
+ * In sleep mode, no measurements are taken and the sensor uses the least power
+ * In forced mode, one measurement is taken before the sensor goes to sleep. To trigger the next measurement, the @ref BMP280_trigger_measurement should be called first.
+ * In normal mode, a measurements is taken followed by a standby period set using @ref BMP280_Standby_Duration_e. This cycle repeats continuously.
+ * @param temperature_oversampling the oversampling to apply to the measurement, higher is cleaner, but takes more time.
+ * @param pressure_oversampling the oversampling to apply to the measurement, higher is cleaner, but takes more time.
+ * @param filter the filtering to apply to the temperature and pressure measurements.
+ * @param standby_duration the standby duration to apply in normal mode after a measurement has been performed.
+ * @return true if the configuration was successful
+ * @return false otherwise
+ */
 bool BMP280_configure(BMP280_Mode_e mode, BMP280_Oversampling_e temperature_oversampling, BMP280_Oversampling_e pressure_oversampling, BMP280_Filter_e filter, BMP280_Standby_Duration_e standby_duration);
 
+/**
+ * @brief Tells the sensor to perform a new measurement. This has to be called when the sensor is configured in the forced operating mode. 
+ * 
+ * @return true if a new measurement was triggered successfully
+ * @return false otherwise
+ */
 bool BMP280_trigger_measurement(void);
 
+/**
+ * @brief Returns the previously sampled temperature in °C.
+ * 
+ * @return float the value of the temperature in °C
+ */
 float BMP280_get_temperature(void);
 
-float BMP280_get_pressure(void);
+/**
+ * @brief Returns the previously sampled pressure in Pa.
+ * 
+ * @param temperature the address of a float which will contain the measured temperature. If not needed, can be NULL.
+ * @return float the value of the pressure in Pa
+ */
+float BMP280_get_pressure(float * const temperature);
 
+/**
+ * @brief Returns an approximation of the altitude using the measured atmospheric pressure.
+ * 
+ * @param pressureAtSeeLevel the current atmospheric pressure at see level in hPa. Can be 0 if unknown and a default value of 1013.25 hPa will be used.
+ * @param pressure the address of a float which will contain the measured pressure. If not needed, can be NULL.
+ * @param temperature the address of a float which will contain the measured temperature. If not needed, can be NULL.
+ * @return float the altitude in meters
+ */
+float BMP280_get_altitude(float pressureAtSeeLevel, float * const pressure, float * const temperature);
+
+/**
+ * @brief Issues a software reset of the sensor.
+ * 
+ * @return true on success
+ * @return false on failure
+ */
 bool BMP280_software_reset(void);
 
 #endif //BMP280_H