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8.6 KiB
8.6 KiB
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 | 3.5.9 | 19 Jun 2018 |
| bme680.h | 3.5.9 | 19 Jun 2018 |
| bme680_defs.h | 3.5.9 | 19 Jun 2018 |
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 bme680_dev gas_sensor;
/* 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 bme680_dev gas_sensor;
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
uint8_t set_required_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 user_delay_ms(uint32_t period)
{
/*
* Return control or wait,
* for a period amount of milliseconds
*/
}
int8_t user_spi_read(uint8_t dev_id, uint8_t reg_addr, uint8_t *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;
}
int8_t user_spi_write(uint8_t dev_id, uint8_t reg_addr, uint8_t *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;
}
int8_t user_i2c_read(uint8_t dev_id, uint8_t reg_addr, uint8_t *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;
}
int8_t user_i2c_write(uint8_t dev_id, uint8_t reg_addr, uint8_t *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;
}