README.md
BME680 sensor API

Introduction

This package contains the Bosch Sensortec's BME680 gas sensor API

The sensor driver package includes bme680.h, bme680.c and bme680_defs.h files

Version




  
File
  
Version
  
Date




  
bme680.c
  
3.5.10
  
23 Jan 2020


  
bme680.h
  
3.5.10
  
23 Jan 2020


  
bme680_defs.h
  
3.5.10
  
23 Jan 2020




Integration details


Integrate bme680.h, bme680_defs.h and bme680.c file in to your project.
Include the bme680.h file in your code like below.


#include "bme680.h"


File information


bme680_defs.h : This header file has the constants, macros and datatype declarations.
bme680.h : This header file contains the declarations of the sensor driver APIs.
bme680.c : This source file contains the definitions of the sensor driver APIs.


Supported sensor interfaces


SPI 4-wire
I2C


Usage guide

Initializing the sensor

To initialize the sensor, you will first need to create a device structure. You 
can do this by creating an instance of the structure bme680_dev. Then go on to 
fill in the various parameters as shown below

Example for SPI 4-Wire

    struct bme680dev gassensor;


/* You may assign a chip select identifier to be handled later */
gas_sensor.dev_id = 0;
gas_sensor.intf = BME680_SPI_INTF;
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);




Example for I2C

    struct bme680dev gassensor;


gas_sensor.dev_id = BME680_I2C_ADDR_PRIMARY;
gas_sensor.intf = BME680_I2C_INTF;
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);




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

    uint8t setrequired_settings;


/* Set the temperature, pressure and humidity settings */
gas_sensor.tph_sett.os_hum = BME680_OS_2X;
gas_sensor.tph_sett.os_pres = BME680_OS_4X;
gas_sensor.tph_sett.os_temp = BME680_OS_8X;
gas_sensor.tph_sett.filter = BME680_FILTER_SIZE_3;

/* Set the remaining gas sensor settings and link the heating profile */
gas_sensor.gas_sett.run_gas = BME680_ENABLE_GAS_MEAS;
/* Create a ramp heat waveform in 3 steps */
gas_sensor.gas_sett.heatr_temp = 320; /* degree Celsius */
gas_sensor.gas_sett.heatr_dur = 150; /* milliseconds */

/* Select the power mode */
/* Must be set before writing the sensor configuration */
gas_sensor.power_mode = BME680_FORCED_MODE; 

/* Set the required sensor settings needed */
set_required_settings = BME680_OST_SEL | BME680_OSP_SEL | BME680_OSH_SEL | BME680_FILTER_SEL 
    | BME680_GAS_SENSOR_SEL;

/* Set the desired sensor configuration */
rslt = bme680_set_sensor_settings(set_required_settings,&gas_sensor);

/* Set the power mode */
rslt = bme680_set_sensor_mode(&gas_sensor);




Reading sensor data

Example for reading all sensor data

    /* Get the total measurement duration so as to sleep or wait till the
     * measurement is complete */
    uint16_t meas_period;
    bme680_get_profile_dur(&meas_period, &gas_sensor);


struct bme680_field_data data;

while(1)
{
    user_delay_ms(meas_period); /* Delay till the measurement is ready */

    rslt = bme680_get_sensor_data(&data, &gas_sensor);

    printf("T: %.2f degC, P: %.2f hPa, H %.2f %%rH ", data.temperature / 100.0f,
        data.pressure / 100.0f, data.humidity / 1000.0f );
    /* Avoid using measurements from an unstable heating setup */
    if(data.status & BME680_GASM_VALID_MSK)
        printf(", G: %d ohms", data.gas_resistance);

    printf("\r\n");

    /* Trigger the next measurement if you would like to read data out continuously */
    if (gas_sensor.power_mode == BME680_FORCED_MODE) {
        rslt = bme680_set_sensor_mode(&gas_sensor);
    }
}




Templates for function pointers

void userdelayms(uint32_t period)
{
    /*
     * Return control or wait,
     * for a period amount of milliseconds
     */
}


int8t userspiread(uint8t devid, uint8t regaddr, uint8t reg_data, uint16_t len)
{
    int8_t rslt = 0; / Return 0 for Success, non-zero for failure */

/*
 * The parameter dev_id can be used as a variable to select which Chip Select pin has
 * to be set low to activate the relevant device on the SPI bus
 */

/*
 * Data on the bus should be like
 * |----------------+---------------------+-------------|
 * | MOSI           | MISO                | Chip Select |
 * |----------------+---------------------|-------------|
 * | (don't care)   | (don't care)        | HIGH        |
 * | (reg_addr)     | (don't care)        | LOW         |
 * | (don't care)   | (reg_data[0])       | LOW         |
 * | (....)         | (....)              | LOW         |
 * | (don't care)   | (reg_data[len - 1]) | LOW         |
 * | (don't care)   | (don't care)        | HIGH        |
 * |----------------+---------------------|-------------|
 */

return rslt;


}

int8t userspiwrite(uint8t devid, uint8t regaddr, uint8t reg_data, uint16_t len)
{
    int8_t rslt = 0; / Return 0 for Success, non-zero for failure */

/*
 * The parameter dev_id can be used as a variable to select which Chip Select pin has
 * to be set low to activate the relevant device on the SPI bus
 */

/*
 * Data on the bus should be like
 * |---------------------+--------------+-------------|
 * | MOSI                | MISO         | Chip Select |
 * |---------------------+--------------|-------------|
 * | (don't care)        | (don't care) | HIGH        |
 * | (reg_addr)          | (don't care) | LOW         |
 * | (reg_data[0])       | (don't care) | LOW         |
 * | (....)              | (....)       | LOW         |
 * | (reg_data[len - 1]) | (don't care) | LOW         |
 * | (don't care)        | (don't care) | HIGH        |
 * |---------------------+--------------|-------------|
 */

return rslt;


}

int8t useri2cread(uint8t devid, uint8t regaddr, uint8t reg_data, uint16_t len)
{
    int8_t rslt = 0; / Return 0 for Success, non-zero for failure */

/*
 * The parameter dev_id can be used as a variable to store the I2C address of the device
 */

/*
 * Data on the bus should be like
 * |------------+---------------------|
 * | I2C action | Data                |
 * |------------+---------------------|
 * | Start      | -                   |
 * | Write      | (reg_addr)          |
 * | Stop       | -                   |
 * | Start      | -                   |
 * | Read       | (reg_data[0])       |
 * | Read       | (....)              |
 * | Read       | (reg_data[len - 1]) |
 * | Stop       | -                   |
 * |------------+---------------------|
 */

return rslt;


}

int8t useri2cwrite(uint8t devid, uint8t regaddr, uint8t reg_data, uint16_t len)
{
    int8_t rslt = 0; / Return 0 for Success, non-zero for failure */

/*
 * The parameter dev_id can be used as a variable to store the I2C address of the device
 */

/*
 * Data on the bus should be like
 * |------------+---------------------|
 * | I2C action | Data                |
 * |------------+---------------------|
 * | Start      | -                   |
 * | Write      | (reg_addr)          |
 * | Write      | (reg_data[0])       |
 * | Write      | (....)              |
 * | Write      | (reg_data[len - 1]) |
 * | Stop       | -                   |
 * |------------+---------------------|
 */

return rslt;


}



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