- Compensation equation in "calc_pressure" API updated

- Corrected get_gas_config API corrected
- Integer lookup tables kept inside "calc_gas_resistance" API
- Added documentation for initialization of the amb_temp parameter
- Removed changelog
- Corrected typos

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      |  3.5.7	| 05 Feb 2018
+bme680.c      |  3.5.8	| 22 Feb 2018
-bme680.h      |  3.5.7	| 05 Feb 2018
+bme680.h      |  3.5.8	| 22 Feb 2018
-bme680_defs.h |  3.5.7	| 05 Feb 2018  
+bme680_defs.h |  3.5.8	| 22 Feb 2018  
 
 ## Integration details
 * Integrate bme680.h, bme680_defs.h and bme680.c file in to your project.
@@ -43,6 +43,10 @@ fill in the various parameters as shown below
 	gas_sensor.read = user_spi_read;
 	gas_sensor.write = user_spi_write;
 	gas_sensor.delay_ms = user_delay_ms;
+    /* amb_temp can be set to 25 prior to configuring the gas sensor 
+     * or by performing a few temperature readings without operating the gas sensor.
+     */
+	gas_sensor.amb_temp = 25;
 
 	int8_t rslt = BME680_OK;
 	rslt = bme680_init(&gas_sensor);
@@ -57,6 +61,11 @@ fill in the various parameters as shown below
 	gas_sensor.read = user_i2c_read;
 	gas_sensor.write = user_i2c_write;
 	gas_sensor.delay_ms = user_delay_ms;
+    /* amb_temp can be set to 25 prior to configuring the gas sensor 
+     * or by performing a few temperature readings without operating the gas sensor.
+     */
+	gas_sensor.amb_temp = 25;
+
 
 	int8_t rslt = BME680_OK;
 	rslt = bme680_init(&gas_sensor);

bme680.c

@@ -40,8 +40,8 @@
  * patent rights of the copyright holder.
  *
  * File		bme680.c
- * @date	05 Feb 2018
+ * @date	22 Feb 2018
- * @version	3.5.7
+ * @version	3.5.8
  *
  */
 
@@ -49,18 +49,6 @@
  @brief Sensor driver for BME680 sensor */
 #include "bme680.h"
 
-/**static variables */
-/**Look up table for the possible gas range values */
-uint32_t lookupTable1[16] = { UINT32_C(2147483647), UINT32_C(2147483647), UINT32_C(2147483647), UINT32_C(2147483647),
-	UINT32_C(2147483647), UINT32_C(2126008810), UINT32_C(2147483647), UINT32_C(2130303777), UINT32_C(2147483647),
-	UINT32_C(2147483647), UINT32_C(2143188679), UINT32_C(2136746228), UINT32_C(2147483647), UINT32_C(2126008810),
-	UINT32_C(2147483647), UINT32_C(2147483647) };
-/**Look up table for the possible gas range values */
-uint32_t lookupTable2[16] = { UINT32_C(4096000000), UINT32_C(2048000000), UINT32_C(1024000000), UINT32_C(512000000),
-	UINT32_C(255744255), UINT32_C(127110228), UINT32_C(64000000), UINT32_C(32258064), UINT32_C(16016016), UINT32_C(
-		8000000), UINT32_C(4000000), UINT32_C(2000000), UINT32_C(1000000), UINT32_C(500000), UINT32_C(250000),
-	UINT32_C(125000) };
-
 /*!
  * @brief This internal API is used to read the calibrated data from the sensor.
  *
@@ -90,6 +78,8 @@ static int8_t set_gas_config(struct bme680_dev *dev);
 
 /*!
  * @brief This internal API is used to get the gas configuration of the sensor.
+ * @note heatr_temp and heatr_dur values are currently register data
+ * and not the actual values set
  *
  * @param[in] dev	:Structure instance of bme680_dev.
  *
@@ -606,7 +596,7 @@ int8_t bme680_set_sensor_mode(struct bme680_dev *dev)
 	/* Check for null pointer in the device structure*/
 	rslt = null_ptr_check(dev);
 	if (rslt == BME680_OK) {
-		/* Call recursively until in sleep */
+		/* Call repeatedly until in sleep */
 		do {
 			rslt = bme680_get_regs(BME680_CONF_T_P_MODE_ADDR, &tmp_pow_mode, 1, dev);
 			if (rslt == BME680_OK) {
@@ -843,6 +833,8 @@ static int8_t set_gas_config(struct bme680_dev *dev)
 
 /*!
  * @brief This internal API is used to get the gas configuration of the sensor.
+ * @note heatr_temp and heatr_dur values are currently register data
+ * and not the actual values set
  */
 static int8_t get_gas_config(struct bme680_dev *dev)
 {
@@ -850,8 +842,7 @@ static int8_t get_gas_config(struct bme680_dev *dev)
 	/* starting address of the register array for burst read*/
 	uint8_t reg_addr1 = BME680_ADDR_SENS_CONF_START;
 	uint8_t reg_addr2 = BME680_ADDR_GAS_CONF_START;
-	uint8_t data_array[BME680_GAS_HEATER_PROF_LEN_MAX] = { 0 };
+	uint8_t reg_data = 0;
-	uint8_t index;
 
 	/* Check for null pointer in the device structure*/
 	rslt = null_ptr_check(dev);
@@ -862,16 +853,14 @@ static int8_t get_gas_config(struct bme680_dev *dev)
 		}
 
 		if (rslt == BME680_OK) {
-			rslt = bme680_get_regs(reg_addr1, data_array, BME680_GAS_HEATER_PROF_LEN_MAX, dev);
+			rslt = bme680_get_regs(reg_addr1, &reg_data, 1, dev);
 			if (rslt == BME680_OK) {
-				for (index = 0; index < BME680_GAS_HEATER_PROF_LEN_MAX; index++)
+				dev->gas_sett.heatr_temp = reg_data;
-					dev->gas_sett.heatr_temp = data_array[index];
+				rslt = bme680_get_regs(reg_addr2, &reg_data, 1, dev);
+				if (rslt == BME680_OK) {
+					/* Heating duration register value */
+					dev->gas_sett.heatr_dur = reg_data;
 				}
-
-			rslt = bme680_get_regs(reg_addr2, data_array, BME680_GAS_HEATER_PROF_LEN_MAX, dev);
-			if (rslt == BME680_OK) {
-				for (index = 0; index < BME680_GAS_HEATER_PROF_LEN_MAX; index++)
-					dev->gas_sett.heatr_dur = data_array[index];
 			}
 		}
 	}
@@ -909,7 +898,6 @@ static uint32_t calc_pressure(uint32_t pres_adc, const struct bme680_dev *dev)
 	int32_t var1 = 0;
 	int32_t var2 = 0;
 	int32_t var3 = 0;
-	int32_t var4 = 0;
 	int32_t pressure_comp = 0;
 
 	var1 = (((int32_t)dev->calib.t_fine) >> 1) - 64000;
@@ -924,8 +912,7 @@ 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 << 30);
+	if (pressure_comp >= BME680_MAX_OVERFLOW_VAL)
-	if (pressure_comp >= var4)
 		pressure_comp = ((pressure_comp / (uint32_t)var1) << 1);
 	else
 		pressure_comp = ((pressure_comp << 1) / (uint32_t)var1);
@@ -989,6 +976,16 @@ static uint32_t calc_gas_resistance(uint16_t gas_res_adc, uint8_t gas_range, con
 	uint64_t var2;
 	int64_t var3;
 	uint32_t calc_gas_res;
+	/**Look up table 1 for the possible gas range values */
+	uint32_t lookupTable1[16] = { UINT32_C(2147483647), UINT32_C(2147483647), UINT32_C(2147483647), UINT32_C(2147483647),
+		UINT32_C(2147483647), UINT32_C(2126008810), UINT32_C(2147483647), UINT32_C(2130303777),
+		UINT32_C(2147483647), UINT32_C(2147483647), UINT32_C(2143188679), UINT32_C(2136746228),
+		UINT32_C(2147483647), UINT32_C(2126008810), UINT32_C(2147483647), UINT32_C(2147483647) };
+	/**Look up table 2 for the possible gas range values */
+	uint32_t lookupTable2[16] = { UINT32_C(4096000000), UINT32_C(2048000000), UINT32_C(1024000000), UINT32_C(512000000),
+		UINT32_C(255744255), UINT32_C(127110228), UINT32_C(64000000), UINT32_C(32258064), UINT32_C(16016016),
+		UINT32_C(8000000), UINT32_C(4000000), UINT32_C(2000000), UINT32_C(1000000), UINT32_C(500000),
+		UINT32_C(250000), UINT32_C(125000) };
 
 	var1 = (int64_t) ((1340 + (5 * (int64_t) dev->calib.range_sw_err)) *
 		((int64_t) lookupTable1[gas_range])) >> 16;

bme680.h

@@ -40,8 +40,8 @@
  * patent rights of the copyright holder.
  *
  * @file	bme680.h
- * @date	05 Feb 2018
+ * @date	22 Feb 2018
- * @version	3.5.7
+ * @version	3.5.8
  * @brief
  *
  */

bme680_defs.h

@@ -40,8 +40,8 @@
  * patent rights of the copyright holder.
  *
  * @file	bme680_defs.h
- * @date	05 Feb 2018
+ * @date	22 Feb 2018
- * @version	3.5.7
+ * @version	3.5.8
  * @brief
  *
  */
@@ -226,7 +226,6 @@
 #define BME680_REG_BUFFER_LENGTH	UINT8_C(6)
 #define BME680_FIELD_DATA_LENGTH	UINT8_C(3)
 #define BME680_GAS_REG_BUF_LENGTH	UINT8_C(20)
-#define BME680_GAS_HEATER_PROF_LEN_MAX  UINT8_C(10)
 
 /** Settings selector */
 #define BME680_OST_SEL			UINT16_C(1)
@@ -317,6 +316,14 @@
 #define BME680_REG_RUN_GAS_INDEX	UINT8_C(1)
 #define BME680_REG_HCTRL_INDEX		UINT8_C(0)
 
+/** BME680 pressure calculation macros */
+/*! This max value is used to provide precedence to multiplication or division
+ * in pressure compensation equation to achieve least loss of precision and
+ * avoiding overflows.
+ * i.e Comparing value, BME680_MAX_OVERFLOW_VAL = INT32_C(1 << 30)
+ */
+#define BME680_MAX_OVERFLOW_VAL      INT32_C(0x40000000)
+
 /** Macro to combine two 8 bit data's to form a 16 bit data */
 #define BME680_CONCAT_BYTES(msb, lsb)	(((uint16_t)msb << 8) | (uint16_t)lsb)
 
@@ -334,7 +341,7 @@
 #define BME680_GET_BITS_POS_0(reg_data, bitname)  (reg_data & (bitname##_MSK))
 
 /** Type definitions */
-/*
+/*!
  * Generic communication function pointer
  * @param[in] dev_id: Place holder to store the id of the device structure
  *                    Can be used to store the index of the Chip select or
@@ -346,7 +353,7 @@
  */
 typedef int8_t (*bme680_com_fptr_t)(uint8_t dev_id, uint8_t reg_addr, uint8_t *data, uint16_t len);
 
-/*
+/*!
  * Delay function pointer
  * @param[in] period: Time period in milliseconds
  */
@@ -489,9 +496,9 @@ struct	bme680_gas_sett {
 	uint8_t heatr_ctrl;
 	/*! Run gas enable value */
 	uint8_t run_gas;
-	/*! Pointer to store heater temperature */
+	/*! Heater temperature value */
 	uint16_t heatr_temp;
-	/*! Pointer to store duration profile */
+	/*! Duration profile value */
 	uint16_t heatr_dur;
 };
 
@@ -521,11 +528,11 @@ struct	bme680_dev {
 	uint8_t new_fields;
 	/*! Store the info messages */
 	uint8_t info_msg;
-	/*! Burst read structure */
+	/*! Bus read function pointer */
 	bme680_com_fptr_t read;
-	/*! Burst write structure */
+	/*! Bus write function pointer */
 	bme680_com_fptr_t write;
-	/*! Delay in ms */
+	/*! delay function pointer */
 	bme680_delay_fptr_t delay_ms;
 	/*! Communication function result */
 	int8_t com_rslt;

changelog.md

@@ -1,66 +0,0 @@
-# Change Log
-All notable changes to the BME680 Sensor API will be documented in this file.
-
-## v3.5.7, 05 Feb 2018
-### Fixed
- - Integer overflow issue fixed in "calc_pressure" API
-
-## 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
-
-## v3.5.4, 16 Nov 2017
-### Changed
- - Updated the set/get gas profile duration logic
-
-## v3.5.3, 30 Oct 2017
-### Changed
- - Changed the compensation equation formulae to use shifting operation
- - Updated the "bme680_get_profile_dur" API
- - Fixed Checkpatch and made linux compatible
-
-## v3.5.2, 18 Oct 2017
-### Changed
- - Fixed bug of temperature compensation in pressure
- 
-## v3.5.1, 5 Jul 2017
-### Changed
- - Fixed bug with overwriting of the result with communication results
- - Added member in the dev structure to store communication results
- - Updated set profile duration API to not return a result.
- - Added new API to get the duration for the existing profile
- - Fixed bug with setting gas configuration. Reduced to writing only relevant bytes
- - Updated readme
- - Updated documentation for the type definitions
- - Removed mode check for get sensor data and setting and getting profile dur
- 
-## v3.5.0, 28 Jun 2017
-### Changed
-- Fixed bug with getting and setting mem pages
-- Changed initialization sequence to be more robust
-- Added additional tries while reading data in case of inadequate delay
-
-## v3.4.0, 8 Jun 2017
-### Changed
-- Modified the bme680_get_sensor_data API. User has to now pass the struct that stores the data rather than retrieving from the bme680_dev structure.
-- Fixed possible bugs
-
-## v3.3.0, 24 May 2017
-### Changed
-- Name changes in the BME680 device structure.
-- Removed sequential and parallel modes.
-- Removed ODR related sensor settings
-- Modified get sensor settings API with user selection.
-- Removed sort sensor data and swap fields API which are not required.
-
-### Added
-- BME680 set profile duration API.
-
-## v3.2.1, 17 May 2017
-### Added
-- Took the reference as base version 3.2.1 of BME680 sensor and added.