bme280.c File Reference

#include <util/delay.h>
#include "bme280.h"
#include "atmega_i2c.h"
#include "log_system.h"

Go to the source code of this file.

Macros
#define	BME280_ADDRESS_W   0xEC
#define	BME280_ADDRESS_R   0xED
#define	CONFIG_REG   0xF5
#define	CTRL_MEAS_REG   0xF4
#define	STATUS_REG   0xF3
#define	CTRL_HUM_REG   0xF2
#define	SOFT_RESET_REG   0xE0
#define	CHIP_ID_REG   0xD0
#define	SKIPPED   0
#define	OVERSAMPLE_x1   1
#define	OVERSAMPLE_x2   2
#define	OVERSAMPLE_x4   3
#define	OVERSAMPLE_x8   4
#define	OVERSAMPLE_x16   5
#define	SLEEP_MODE   0
#define	FORCED_MODE   1
#define	NORMAL_MODE   3
#define	BUS_SPEED_100KHZ   100000U

Functions
void	bme280_write_byte (uint8_t reg, uint8_t byte)
	Writes a single byte to a specified reguster. More...
void	bme280_write_word (uint8_t reg1, uint8_t reg2, uint8_t msb, uint8_t lsb)
uint16_t	bme280_read_word (uint8_t start_address)
	Reads a 16bit unsigned integer from a specified register. More...
uint8_t	bme280_read_byte (uint8_t reg)
void	bme280_read_comp_data (void)
	Reads in all compensation data from the device and stores it in a buffer. More...
uint32_t	bme280_get_raw_temp_val (void)
uint32_t	bme280_get_raw_hum_val (void)
void	bme280_burst_read (uint8_t start_addr, uint8_t start_position, uint8_t length)
int32_t	bme280_compensate_temp (int32_t adc_T)
	Returns temperature in DegC, resolution is 0.01 DegC. More...
int32_t	bme280_compensate_pressure (int32_t adc_P)
	Returns pressure in Pa as unsigned 32 bit integer. More...
uint32_t	bme280_compensate_humidity (int32_t adc_H)
	Returns humidity in RH as unsigned 32 bit integer in Q22.10 format (22 integer and 10 fractional bits). More...
void	init_bme280 (void)
	Initialise the device ready for measurements to be taken. More...
int16_t	bme280_get_temperature (void)
	Fetches the latest temperature data from the sensor, compensates and formats the data in degrees Celcius * 100. More...
uint16_t	bme280_get_humidity (void)
	Fetches the latest humidity data from the sensor, compensates and formats the data as RH * 100. More...
uint16_t	bme280_get_pressure (void)
	Fetches the latest pressure data from the sensor, compensates and formats the data as Pa * 100. More...

Variables
log_system_config_t	bme280_log
int32_t	t_fine

Detailed Description

Copyright

Copyright © 2022 by Jason Duffy.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Author

Jason Duffy

Date

22nd June 2022

Definition in file bme280.c.

Macro Definition Documentation

BME280_ADDRESS_W

#define BME280_ADDRESS_W   0xEC

Definition at line 40 of file bme280.c.

BME280_ADDRESS_R

#define BME280_ADDRESS_R   0xED

Definition at line 41 of file bme280.c.

CONFIG_REG

#define CONFIG_REG   0xF5

Definition at line 44 of file bme280.c.

CTRL_MEAS_REG

#define CTRL_MEAS_REG   0xF4

Definition at line 45 of file bme280.c.

STATUS_REG

#define STATUS_REG   0xF3

Definition at line 46 of file bme280.c.

CTRL_HUM_REG

#define CTRL_HUM_REG   0xF2

Definition at line 47 of file bme280.c.

SOFT_RESET_REG

#define SOFT_RESET_REG   0xE0

Definition at line 49 of file bme280.c.

CHIP_ID_REG

#define CHIP_ID_REG   0xD0

Definition at line 50 of file bme280.c.

SKIPPED

#define SKIPPED   0

Definition at line 53 of file bme280.c.

OVERSAMPLE_x1

#define OVERSAMPLE_x1   1

Definition at line 54 of file bme280.c.

OVERSAMPLE_x2

#define OVERSAMPLE_x2   2

Definition at line 55 of file bme280.c.

OVERSAMPLE_x4

#define OVERSAMPLE_x4   3

Definition at line 56 of file bme280.c.

OVERSAMPLE_x8

#define OVERSAMPLE_x8   4

Definition at line 57 of file bme280.c.

OVERSAMPLE_x16

#define OVERSAMPLE_x16   5

Definition at line 58 of file bme280.c.

SLEEP_MODE

#define SLEEP_MODE   0

Definition at line 60 of file bme280.c.

FORCED_MODE

#define FORCED_MODE   1

Definition at line 61 of file bme280.c.

NORMAL_MODE

#define NORMAL_MODE   3

Definition at line 62 of file bme280.c.

BUS_SPEED_100KHZ

#define BUS_SPEED_100KHZ   100000U

Definition at line 64 of file bme280.c.

Function Documentation

bme280_write_byte()

void bme280_write_byte	(	uint8_t	reg,
		uint8_t	byte
	)

Writes a single byte to a specified reguster.

Parameters

reg	is the reguster to be written to.
byte	is the data to be sent.

Definition at line 244 of file bme280.c.

{
    i2c_start();
    i2c_send(BME280_ADDRESS_W);
    i2c_send(reg);
    i2c_send(byte);
    i2c_stop();
}

bme280_read_word()

uint16_t bme280_read_word

(

uint8_t

start_address

)

Reads a 16bit unsigned integer from a specified register.

Parameters

start_address

is the first memory location to be read from.

Returns

The data read from the device is returned.

Definition at line 295 of file bme280.c.

{
    unsigned short msb;
    unsigned short lsb;
    unsigned short word;
 
    i2c_start();
    i2c_send(BME280_ADDRESS_W);
    i2c_send(start_address);
    i2c_start();
    i2c_send(BME280_ADDRESS_R);
 
    lsb = i2c_read_ack();
    msb = i2c_read_no_ack();
    i2c_stop();
 
    word = (msb << 8);
    word |= lsb;
    return word;
}

bme280_read_byte()

uint8_t bme280_read_byte

(

uint8_t

reg

)

Definition at line 254 of file bme280.c.

{
    uint8_t byte;
 
    i2c_start();
    i2c_send(BME280_ADDRESS_W);
    i2c_send(reg);
    i2c_start();
    i2c_send(BME280_ADDRESS_R);
    byte = i2c_read_no_ack();
    i2c_stop();
    return byte;
}

bme280_read_comp_data()

void bme280_read_comp_data

(

void

)

Reads in all compensation data from the device and stores it in a buffer.

Definition at line 322 of file bme280.c.

{
    signed short h_lsb;
    signed short h_msb;
 
    // Read and store temperature compensation data. 
    dig_T1 = bme280_read_word(0x88);
    dig_T2 = bme280_read_word(0x8A);
    dig_T3 = bme280_read_word(0x8C);
 
    // Read and store pressure compensation data.
    dig_P1 = bme280_read_word(0x8E);
    dig_P2 = bme280_read_word(0x90);
    dig_P3 = bme280_read_word(0x92);
    dig_P4 = bme280_read_word(0x94);
    dig_P5 = bme280_read_word(0x96);
    dig_P6 = bme280_read_word(0x98);
    dig_P7 = bme280_read_word(0x9A);
    dig_P8 = bme280_read_word(0x9C);
    dig_P9 = bme280_read_word(0x9E);
 
    // Read and store humidity compensation data.
    dig_H1 = bme280_read_byte(0xA1);
    dig_H2 = bme280_read_word(0xE1);
    dig_H3 = bme280_read_byte(0xE3);
 
    h_msb = bme280_read_byte(0xE4);
    h_lsb = bme280_read_byte(0xE5);
    h_lsb &= 0b00001111;
    dig_H4 = h_lsb;
    dig_H4 |= (h_msb << 4);
 
    h_msb = bme280_read_byte(0xE6);
    h_lsb = bme280_read_byte(0xE5);
    h_lsb &= 0b11110000;
    dig_H5 = (h_lsb >> 4);
    dig_H5 |= (h_msb << 4);
 
    dig_H6 = bme280_read_byte(0xE7);
}

bme280_get_raw_temp_val()

uint32_t bme280_get_raw_temp_val

(

void

)

Definition at line 364 of file bme280.c.

{
    uint32_t retval;
    uint32_t temp_msb;
    uint32_t temp_lsb;
    uint32_t temp_xlsb;
 
    i2c_start();
    i2c_send(BME280_ADDRESS_W);
    i2c_send(0xFA);
    i2c_start();
    i2c_send(BME280_ADDRESS_R);
    temp_msb = i2c_read_ack();
    temp_lsb = i2c_read_ack();
    temp_xlsb = i2c_read_no_ack();
    i2c_stop();
 
    retval = temp_msb << 12;
    retval |= temp_lsb << 4;
    retval |= temp_xlsb >> 4;
 
    return retval;
}

bme280_get_raw_hum_val()

uint32_t bme280_get_raw_hum_val

(

void

)

Definition at line 388 of file bme280.c.

{
    uint32_t retval;
    uint16_t hum_msb;
    uint16_t hum_lsb;
 
    i2c_start();
    i2c_send(BME280_ADDRESS_W);
    i2c_send(0xFD);
    i2c_start();
    i2c_send(BME280_ADDRESS_R);
    hum_msb = i2c_read_ack();
    hum_lsb = i2c_read_no_ack();
    i2c_stop();
 
    retval = hum_msb << 8;
    retval |= hum_lsb;
 
    return retval;
}

bme280_burst_read()

void bme280_burst_read	(	uint8_t	start_addr,
		uint8_t	start_position,
		uint8_t	length
	)

Definition at line 269 of file bme280.c.

{
    i2c_start();
    i2c_send(BME280_ADDRESS_W);
    i2c_send(start_address);
    i2c_start();
    i2c_send(BME280_ADDRESS_R);
 
    int i;
    for (i = 0; i < (length - 1); ++i)
    {
        BME280_read_buffer[i] = i2c_read_ack();
    }
    BME280_read_buffer[i] = i2c_read_no_ack();
 
    i2c_stop();
}

bme280_compensate_temp()

int32_t bme280_compensate_temp

(

int32_t

adc_T

)

Returns temperature in DegC, resolution is 0.01 DegC.

Output value of "5123" equals 51.23 DegC.

Definition at line 420 of file bme280.c.

{
    int32_t var1, var2, T;
    var1 = (((adc_T >> 3) - ((int32_t)dig_T1 << 1)) * ((int32_t)dig_T2)) >> 11;
    var2 = (((((adc_T >> 4) - ((int32_t)dig_T1)) * ((adc_T >> 4) 
    - ((int32_t)dig_T1))) >> 12) * ((int32_t)dig_T3)) >> 14;
    t_fine = var1 + var2;
    T = (t_fine * 5 + 128) >> 8;
    return T;
}

bme280_compensate_pressure()

int32_t bme280_compensate_pressure

(

int32_t

adc_P

)

Returns pressure in Pa as unsigned 32 bit integer.

Output value of "96386" equals 96386 Pa = 963.86 hPa.

Definition at line 436 of file bme280.c.

{
    int32_t var1, var2;
    uint32_t p;
    var1 = (t_fine >> 1) - 64000;
    var2 = (((var1 >> 2) * (var1 >> 2)) >> 11 ) * ((int32_t)dig_P6);
    var2 = var2 + ((var1 * ((int32_t)dig_P5)) << 1);
    var2 = (var2 >> 2) + (((int32_t)dig_P4) << 16);
    var1 = ((((int32_t)dig_P3 * (((var1 >> 2) * (var1 >> 2)) >> 13 )) >> 3)
    + (((((int32_t)dig_P2) * var1) >> 1 ))) >> 18;
    var1 = ((((32768 + var1)) * ((int32_t)dig_P1)) >> 15);
 
    if (var1 == 0)
    {
        return 0; // avoid exception caused by division by zero
    }
 
    p = ((((1048576) - adc_P) - (var2 >> 12))) * 3125;
 
    if (p < 0x80000000)
    {
        p = (p << 1) / (var1);
    }
 
    else
    {
        p = (p / var1) * 2;
    }
 
    var1 = ((dig_P9) * ((((p>>3) * (p >> 3)) >> 13))) >> 12;
    var2 = (((p >> 2)) * (dig_P8)) >> 13;
    p = (p + ((var1 + var2 + dig_P7) >> 4));
    return p;
}

bme280_compensate_humidity()

uint32_t bme280_compensate_humidity

(

int32_t

adc_H

)

Returns humidity in RH as unsigned 32 bit integer in Q22.10 format (22 integer and 10 fractional bits).

Output value of "47445" represents 47445/1024 = 46.333 RH.

Definition at line 477 of file bme280.c.

{
    int32_t v_x1_u32r;
 
    v_x1_u32r = (t_fine - (76800));
 
    v_x1_u32r = (((((adc_H << 14) - (((int32_t)dig_H4) << 20)
    - (((int32_t)dig_H5) * v_x1_u32r)) + (16384)) >> 15) * (((((((v_x1_u32r 
    * ((int32_t)dig_H6)) >> 10) * (((v_x1_u32r * ((int32_t)dig_H3)) >> 11)
    + (32768))) >> 10) + (2097152)) * ((int32_t)dig_H2) + 8192) >> 14));
 
    v_x1_u32r = (v_x1_u32r - (((((v_x1_u32r >> 15) * (v_x1_u32r >> 15)) >> 7)
    * ((int32_t)dig_H1)) >> 4));
    v_x1_u32r = (v_x1_u32r < 0 ? 0 : v_x1_u32r);
    v_x1_u32r = (v_x1_u32r > 419430400 ? 419430400 : v_x1_u32r);
    return (uint32_t)(v_x1_u32r>>12);
}

init_bme280()

void init_bme280

(

void

)

Initialise the device ready for measurements to be taken.

Definition at line 125 of file bme280.c.

{   
    // Setup I2C hardware fpr use.
    init_i2c(BUS_SPEED_100KHZ);
 
    // Perform ID check. 
    uint8_t id = bme280_read_byte(CHIP_ID_REG);
    if (id == 0x60)
    {
        log_message(&bme280_log,
                    DEBUG,
                    "In init_bme280(), Chip ID check passed.");
    }
    else
    {
        log_message(&bme280_log,
                    ERROR,
                    "In init_bme280(), Chip ID check failed.");
    }
 
    // Read compensation data from sensor and save it.
    bme280_read_comp_data();
 
    // 
    bme280_write_byte(CTRL_HUM_REG, OVERSAMPLE_x1);
 
    //
    bme280_write_byte(CONFIG_REG, 0b10100000);
 
    // oversample x1 temp, pressure off, forced mode
    bme280_write_byte(CTRL_MEAS_REG, 0b00100001);
}

bme280_get_temperature()

int16_t bme280_get_temperature

(

void

)

Fetches the latest temperature data from the sensor, compensates and formats the data in degrees Celcius * 100.

Returns

eg. A return value of 5123 = 51.23˚C (Degrees Celcius).

Definition at line 164 of file bme280.c.

{
    int32_t retval;
    uint32_t raw_temp_adc_val;
 
    // oversample x1 temp, pressure off, forced mode.
    bme280_write_byte(CTRL_MEAS_REG, 0b00100001);
    raw_temp_adc_val = bme280_get_raw_temp_val();
    retval = bme280_compensate_temp(raw_temp_adc_val);
 
    return retval;
}

bme280_get_humidity()

uint16_t bme280_get_humidity

(

void

)

Fetches the latest humidity data from the sensor, compensates and formats the data as RH * 100.

Returns

eg. A return value of 2852 = 28.50 RH (Relative Humidity).

Definition at line 207 of file bme280.c.

{
    uint32_t retval;
    uint16_t raw_hum_adc_val;
 
    // oversample x1 temp, pressure off, forced mode
    bme280_write_byte(CTRL_MEAS_REG, 0b00100001);
    raw_hum_adc_val = bme280_get_raw_hum_val();
    retval = bme280_compensate_humidity(raw_hum_adc_val);
    retval *= 100;
    retval = (retval >> 10);
 
    return retval;
}

bme280_get_pressure()

uint16_t bme280_get_pressure

(

void

)

Fetches the latest pressure data from the sensor, compensates and formats the data as Pa * 100.

Returns

eg. A return value of 96386 = 963.86 Pa (Pascals).

Definition at line 228 of file bme280.c.

{
    // Some pressure-getting code goes here.
    return 0; 
}

Variable Documentation

bme280_log

log_system_config_t bme280_log

Initial value:

= 
{
    .p_system_tag = "BME280",
    .file_log_level = DEBUG,
}

Definition at line 66 of file bme280.c.

t_fine

int32_t t_fine

Definition at line 414 of file bme280.c.