- Floating point support added for the API

- Lower temperature cap removed in "calc_heater_res" API
 - Added typecast for overflow check in "calc_pressure" API

README.md

@@ -7,9 +7,9 @@ The sensor driver package includes bme680.h, bme680.c and bme680_defs.h files
 ## Version
 File          | Version | Date
 --------------|---------|-------------
-bme680.c      |  3.5.5	| 20 Nov 2017
+bme680.c      |  3.5.6	| 19 Jan 2018
-bme680.h      |  3.5.5	| 20 Nov 2017
+bme680.h      |  3.5.6	| 19 Jan 2018
-bme680_defs.h |  3.5.5	| 20 Nov 2017  
+bme680_defs.h |  3.5.6	| 19 Jan 2018  
 
 ## Integration details
 * Integrate bme680.h, bme680_defs.h and bme680.c file in to your project.
@@ -62,6 +62,16 @@ fill in the various parameters as shown below
 	rslt = bme680_init(&gas_sensor);
 ```
 
+Regarding compensation functions for temperature, pressure, humidity and gas we have two implementations.
+
+    - Integer version
+    - floating point version
+
+By default, Integer version is used in the API
+
+If the user needs the floating point version, the user has to un-comment BME680_FLOAT_POINT_COMPENSATION macro 
+in bme680_defs.h file or to add it in the compiler flags.
+
 ### Configuring the sensor
 #### Example for configuring the sensor in forced mode
 ``` c

bme680.c

@@ -40,8 +40,8 @@
  * patent rights of the copyright holder.
  *
  * File		bme680.c
- * @date	20 Nov 2017
+ * @date	19 Jan 2018
- * @version	3.5.5
+ * @version	3.5.6
  *
  */
 
@@ -107,6 +107,8 @@ static int8_t get_gas_config(struct bme680_dev *dev);
  */
 static uint8_t calc_heater_dur(uint16_t dur);
 
+#ifndef BME680_FLOAT_POINT_COMPENSATION
+
 /*!
  * @brief This internal API is used to calculate the temperature value.
  *
@@ -151,13 +153,72 @@ static uint32_t calc_gas_resistance(uint16_t gas_res_adc, uint8_t gas_range, con
 /*!
  * @brief This internal API is used to calculate the Heat Resistance value.
  *
- * @param[in] dev	:Structure instance of bme680_dev.
+ * @param[in] dev	: Structure instance of bme680_dev
- * @param[in] temp	:Contains the temporary value.
+ * @param[in] temp	: Contains the target temperature value.
  *
  * @return uint8_t calculated heater resistance.
  */
 static uint8_t calc_heater_res(uint16_t temp, const struct bme680_dev *dev);
 
+#else
+/*!
+ * @brief This internal API is used to calculate the
+ * temperature value value in float format
+ *
+ * @param[in] dev	:Structure instance of bme680_dev.
+ * @param[in] temp_adc	:Contains the temperature ADC value .
+ *
+ * @return Calculated temperature in float
+ */
+static float calc_temperature(uint32_t temp_adc, struct bme680_dev *dev);
+
+/*!
+ * @brief This internal API is used to calculate the
+ * pressure value value in float format
+ *
+ * @param[in] dev	:Structure instance of bme680_dev.
+ * @param[in] pres_adc	:Contains the pressure ADC value .
+ *
+ * @return Calculated pressure in float.
+ */
+static float calc_pressure(uint32_t pres_adc, const struct bme680_dev *dev);
+
+/*!
+ * @brief This internal API is used to calculate the
+ * humidity value value in float format
+ *
+ * @param[in] dev	:Structure instance of bme680_dev.
+ * @param[in] hum_adc	:Contains the humidity ADC value.
+ *
+ * @return Calculated humidity in float.
+ */
+static float calc_humidity(uint16_t hum_adc, const struct bme680_dev *dev);
+
+/*!
+ * @brief This internal API is used to calculate the
+ * gas resistance value value in float format
+ *
+ * @param[in] dev		:Structure instance of bme680_dev.
+ * @param[in] gas_res_adc	:Contains the Gas Resistance ADC value.
+ * @param[in] gas_range		:Contains the range of gas values.
+ *
+ * @return Calculated gas resistance in float.
+ */
+static float calc_gas_resistance(uint16_t gas_res_adc, uint8_t gas_range, const struct bme680_dev *dev);
+
+/*!
+ * @brief This internal API is used to calculate the
+ * heater resistance value in float format
+ *
+ * @param[in] temp	: Contains the target temperature value.
+ * @param[in] dev	: Structure instance of bme680_dev.
+ *
+ * @return Calculated heater resistance in float.
+ */
+static float calc_heater_res(uint16_t temp, const struct bme680_dev *dev);
+
+#endif
+
 /*!
  * @brief This internal API is used to calculate the field data of sensor.
  *
@@ -818,6 +879,8 @@ static int8_t get_gas_config(struct bme680_dev *dev)
 	return rslt;
 }
 
+#ifndef BME680_FLOAT_POINT_COMPENSATION
+
 /*!
  * @brief This internal API is used to calculate the temperature value.
  */
@@ -861,7 +924,7 @@ static uint32_t calc_pressure(uint32_t pres_adc, const struct bme680_dev *dev)
 	var1 = ((32768 + var1) * (int32_t)dev->calib.par_p1) >> 15;
 	pressure_comp = 1048576 - pres_adc;
 	pressure_comp = (int32_t)((pressure_comp - (var2 >> 12)) * ((uint32_t)3125));
-	var4 = (1 << 31);
+	var4 = (INT32_C(1) << 31);
 	if (pressure_comp >= var4)
 		pressure_comp = ((pressure_comp / (uint32_t)var1) << 1);
 	else
@@ -949,9 +1012,7 @@ static uint8_t calc_heater_res(uint16_t temp, const struct bme680_dev *dev)
 	int32_t var5;
 	int32_t heatr_res_x100;
 
-	if (temp < 200) /* Cap temperature */
+	if (temp > 400) /* Cap temperature */
-		temp = 200;
-	else if (temp > 400)
 		temp = 400;
 
 	var1 = (((int32_t) dev->amb_temp * dev->calib.par_gh3) / 1000) * 256;
@@ -965,6 +1026,165 @@ static uint8_t calc_heater_res(uint16_t temp, const struct bme680_dev *dev)
 	return heatr_res;
 }
 
+#else
+
+
+/*!
+ * @brief This internal API is used to calculate the
+ * temperature value in float format
+ */
+static float calc_temperature(uint32_t temp_adc, struct bme680_dev *dev)
+{
+	float var1 = 0;
+	float var2 = 0;
+	float calc_temp = 0;
+
+	/* calculate var1 data */
+	var1  = ((((float)temp_adc / 16384.0f) - ((float)dev->calib.par_t1 / 1024.0f))
+			* ((float)dev->calib.par_t2));
+
+	/* calculate var2 data */
+	var2  = (((((float)temp_adc / 131072.0f) - ((float)dev->calib.par_t1 / 8192.0f)) *
+		(((float)temp_adc / 131072.0f) - ((float)dev->calib.par_t1 / 8192.0f))) *
+		((float)dev->calib.par_t3 * 16.0f));
+
+	/* t_fine value*/
+	dev->calib.t_fine = (var1 + var2);
+
+	/* compensated temperature data*/
+	calc_temp  = ((dev->calib.t_fine) / 5120.0f);
+
+	return calc_temp;
+}
+
+/*!
+ * @brief This internal API is used to calculate the
+ * pressure value in float format
+ */
+static float calc_pressure(uint32_t pres_adc, const struct bme680_dev *dev)
+{
+	float var1 = 0;
+	float var2 = 0;
+	float var3 = 0;
+	float calc_pres = 0;
+
+	var1 = (((float)dev->calib.t_fine / 2.0f) - 64000.0f);
+	var2 = var1 * var1 * (((float)dev->calib.par_p6) / (131072.0f));
+	var2 = var2 + (var1 * ((float)dev->calib.par_p5) * 2.0f);
+	var2 = (var2 / 4.0f) + (((float)dev->calib.par_p4) * 65536.0f);
+	var1 = (((((float)dev->calib.par_p3 * var1 * var1) / 16384.0f)
+		+ ((float)dev->calib.par_p2 * var1)) / 524288.0f);
+	var1 = ((1.0f + (var1 / 32768.0f)) * ((float)dev->calib.par_p1));
+	calc_pres = (1048576.0f - ((float)pres_adc));
+
+	/* Avoid exception caused by division by zero */
+	if ((int)var1 != 0) {
+		calc_pres = (((calc_pres - (var2 / 4096.0f)) * 6250.0f) / var1);
+		var1 = (((float)dev->calib.par_p9) * calc_pres * calc_pres) / 2147483648.0f;
+		var2 = calc_pres * (((float)dev->calib.par_p8) / 32768.0f);
+		var3 = ((calc_pres / 256.0f) * (calc_pres / 256.0f) * (calc_pres / 256.0f)
+			* (dev->calib.par_p10 / 131072.0f));
+		calc_pres = (calc_pres + (var1 + var2 + var3 + ((float)dev->calib.par_p7 * 128.0f)) / 16.0f);
+	} else {
+		calc_pres = 0;
+	}
+
+	return calc_pres;
+}
+
+/*!
+ * @brief This internal API is used to calculate the
+ * humidity value in float format
+ */
+static float calc_humidity(uint16_t hum_adc, const struct bme680_dev *dev)
+{
+	float calc_hum = 0;
+	float var1 = 0;
+	float var2 = 0;
+	float var3 = 0;
+	float var4 = 0;
+	float temp_comp;
+
+	/* compensated temperature data*/
+	temp_comp  = ((dev->calib.t_fine) / 5120.0f);
+
+	var1 = (float)((float)hum_adc) - (((float)dev->calib.par_h1 * 16.0f) + (((float)dev->calib.par_h3 / 2.0f)
+		* temp_comp));
+
+	var2 = var1 * ((float)(((float) dev->calib.par_h2 / 262144.0f) * (1.0f + (((float)dev->calib.par_h4 / 16384.0f)
+		* temp_comp) + (((float)dev->calib.par_h5 / 1048576.0f) * temp_comp * temp_comp))));
+
+	var3 = (float) dev->calib.par_h6 / 16384.0f;
+
+	var4 = (float) dev->calib.par_h7 / 2097152.0f;
+
+	calc_hum = var2 + ((var3 + (var4 * temp_comp)) * var2 * var2);
+
+	if (calc_hum > 100.0f)
+		calc_hum = 100.0f;
+	else if (calc_hum < 0.0f)
+		calc_hum = 0.0f;
+
+	return calc_hum;
+}
+
+/*!
+ * @brief This internal API is used to calculate the
+ * gas resistance value in float format
+ */
+static float calc_gas_resistance(uint16_t gas_res_adc, uint8_t gas_range, const struct bme680_dev *dev)
+{
+	float calc_gas_res;
+	float var1 = 0;
+	float var2 = 0;
+	float var3 = 0;
+
+	const float lookup_k1_range[16] = {
+	0.0, 0.0, 0.0, 0.0, 0.0, -1.0, 0.0, -0.8,
+	0.0, 0.0, -0.2, -0.5, 0.0, -1.0, 0.0, 0.0};
+	const float lookup_k2_range[16] = {
+	0.0, 0.0, 0.0, 0.0, 0.1, 0.7, 0.0, -0.8,
+	-0.1, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0};
+
+	var1 = (1340.0f + (5.0f * dev->calib.range_sw_err));
+	var2 = (var1) * (1.0f + lookup_k1_range[gas_range]/100.0f);
+	var3 = 1.0f + (lookup_k2_range[gas_range]/100.0f);
+
+	calc_gas_res = 1.0f / (float)(var3 * (0.000000125f) * (float)(1 << gas_range) * (((((float)gas_res_adc)
+		- 512.0f)/var2) + 1.0f));
+
+	return calc_gas_res;
+}
+
+/*!
+ * @brief This internal API is used to calculate the
+ * heater resistance value in float format
+ */
+static float calc_heater_res(uint16_t temp, const struct bme680_dev *dev)
+{
+	float var1 = 0;
+	float var2 = 0;
+	float var3 = 0;
+	float var4 = 0;
+	float var5 = 0;
+	float res_heat = 0;
+
+	if (temp > 400) /* Cap temperature */
+		temp = 400;
+
+	var1 = (((float)dev->calib.par_gh1 / (16.0f)) + 49.0f);
+	var2 = ((((float)dev->calib.par_gh2 / (32768.0f)) * (0.0005f)) + 0.00235f);
+	var3 = ((float)dev->calib.par_gh3 / (1024.0f));
+	var4 = (var1 * (1.0f + (var2 * (float)temp)));
+	var5 = (var4 + (var3 * (float)dev->amb_temp));
+	res_heat = (uint8_t)(3.4f * ((var5 * (4 / (4 + (float)dev->calib.res_heat_range)) *
+		(1/(1 + ((float) dev->calib.res_heat_val * 0.002f)))) - 25));
+
+	return res_heat;
+}
+
+#endif
+
 /*!
  * @brief This internal API is used to calculate the Heat duration value.
  */

bme680.h

@@ -40,8 +40,8 @@
  * patent rights of the copyright holder.
  *
  * @file	bme680.h
- * @date	20 Nov 2017
+ * @date	19 Jan 2018
- * @version	3.5.5
+ * @version	3.5.6
  * @brief
  *
  */

bme680_defs.h

@@ -40,8 +40,8 @@
  * patent rights of the copyright holder.
  *
  * @file	bme680_defs.h
- * @date	20 Nov 2017
+ * @date	19 Jan 2018
- * @version	3.5.5
+ * @version	3.5.6
  * @brief
  *
  */
@@ -100,6 +100,12 @@
 #endif
 #endif
 
+/** BME680 configuration macros */
+/** Enable or un-comment the macro to provide floating point data output */
+#ifndef BME680_FLOAT_POINT_COMPENSATION
+/* #define BME680_FLOAT_POINT_COMPENSATION */
+#endif
+
 /** BME680 General config */
 #define BME680_POLL_PERIOD_MS		UINT8_C(10)
 
@@ -367,6 +373,8 @@ struct	bme680_field_data {
 	uint8_t gas_index;
 	/*! Measurement index to track order */
 	uint8_t meas_index;
+
+#ifndef BME680_FLOAT_POINT_COMPENSATION
 	/*! Temperature in degree celsius x100 */
 	int16_t temperature;
 	/*! Pressure in Pascal */
@@ -375,6 +383,18 @@ struct	bme680_field_data {
 	uint32_t humidity;
 	/*! Gas resistance in Ohms */
 	uint32_t gas_resistance;
+#else
+	/*! Temperature in degree celsius */
+	float temperature;
+	/*! Pressure in Pascal */
+	float pressure;
+	/*! Humidity in % relative humidity x1000 */
+	float humidity;
+	/*! Gas resistance in Ohms */
+	float gas_resistance;
+
+#endif
+
 };
 
 /*!
@@ -427,8 +447,14 @@ struct	bme680_calib_data {
 	int16_t par_p9;
 	/*! Variable to store calibrated pressure data */
 	uint8_t par_p10;
+
+#ifndef BME680_FLOAT_POINT_COMPENSATION
 	/*! Variable to store t_fine size */
 	int32_t t_fine;
+#else
+	/*! Variable to store t_fine size */
+	float t_fine;
+#endif
 	/*! Variable to store heater resistance range */
 	uint8_t res_heat_range;
 	/*! Variable to store heater resistance value */

changelog.md

@@ -1,6 +1,11 @@
 # Change Log
 All notable changes to the BME680 Sensor API will be documented in this file.
 
+## v3.5.6, 19 Jan 2018
+### Added
+ - Floating point support added for the API
+ - Lower temperature cap removed in "calc_heater_res" APIs
+
 ## v3.5.5, 20 Nov 2017
 ### Changed
  - Updated the buffer size in "get_calib_data" API