Introduction
Welcome to the documentation of STM32 driver for BMP180 barometric pressure/temperature/altitude sensor.
Source code is available at Github.
License
MIT License
Copyright (c) 2022 Ceyhun Şen
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.
Index
Getting Started
Adding to Your Project
Copy
bmp180directory to your projectsdriversdirectory.Add
bmp180.cfile to your projects source files.Add
bmp180/inc/directory to your projects include path.Change
I2C_LIBdefinition inbmp180/inc/bmp180.h(line 14) to your MCU’s I2C HAL library (e.g."stm32f4xx_hal.h").
Units
Temperature: Celsius
Pressure: Pascal
Altitude: Meter
Simple Usage
// Define bmp180_t struct instance
bmp180_t bmp180 = {.oversampling_setting = standart};
// Wait till initialization is complete
while (bmp180_init(&hi2c1, &bmp180));
// Get all the values
bmp180_get_all(&bmp180);
float temperature = bmp180.temperature;
int32_t pressure = bmp180.pressure;
float altitude = bmp180.altitude;
More On Getting Sensor Data
There is actually 2 sensor data: temperature and pressure. Altitude is calculated from pressure data. And each one of them can be measured seperately. But each one of them needs some other data from other calculations.
Pressure data needs some calibration values from temperature measurements.
Altitude calculation needs pressure data.
There are seperate functions for all 3 of them but measuring them seperately may result inaccurate data. So using bmp180_get_all() function is the recommended way. But if you really need to measure them seperately, here is the recommended minimums of function calls:
Temperature
bmp180_get_temperature(&bmp180);
float temperature = bmp180.temperature;
Pressure
bmp180_get_temperature(&bmp180);
bmp180_get_pressure(&bmp180);
int32_t pressure = bmp180.pressure;
Altitude
bmp180_get_temperature(&bmp180);
bmp180_get_pressure(&bmp180);
bmp180_get_altitude(&bmp180);
float altitude = bmp180.altitude;
Oversampling Settings
BMP180 offers hardware oversampling for sensor data. These are ultra low power, standard, high resolution and ultra high resolution. Check BMP180’s datasheet for detailed information about oversampling.
Changing Oversampling Setting
Oversampling setting is stored in the bmp180_t struct. If you want to change oversampling setting, you should change oversampling_setting member and call bmp180_init() function.
For example if you want to change it to ultra high resolution:
bmp180.oversampling_setting = ultra_high_resolution;
bmp180_init(&hi2c1, &bmp180);
Warning
If you don’t call bmp180_init() function after changing setting, oversampling won’t change.
Sea Pressure
Default sea pressure is 101325 pascal.
Changing Sea Pressure
Sea pressure can be changed with modifying sea_pressure member of bmp180_t struct or calling bmp180_set_sea_sressure().
bmp180_set_sea_pressure(&bmp180, 101400);
If you want to measure altitude from any take-off point, first measure pressure at the ground and set it as sea pressure. After that, the new altitude calculation is your altitude from ground.
// ...
// Getting pressure and setting it as sea pressure
bmp180_get_all(&bmp180);
bmp180_set_sea_pressure(&bmp180, bmp180.pressure);
// After take-off, measure altitude
bmp180_get_all(&bmp180);
float higher_altitude_than_ground = bmp180.altitude;
// ...
I2C Interface
BMP180 sensor only supports I2C interface. So, this driver uses STM32’s I2C HAL libraries. If you want to change it to LL drivers, modify bmp180_read(), bmp180_write() and bmp180_is_ready() functions.
API Reference
- Author
Ceyhun Şen
Defines
-
I2C_LIB
Library that includes I2C functions.
Change this definition to your MCU’s I2C HAL library. E.g. “stm32f4xx_hal.h”.
Enums
Functions
-
uint8_t bmp180_init(I2C_HandleTypeDef *hi2cx, bmp180_t *bmp180)
Initialize sensor and get calibration values.
- Parameters
hi2cx – I2C handle.
bmp180 –
bmp180_tstruct to initialize.
- Returns
0 on success, 1 on sensor is not ready, 2 on sensor error.
-
void bmp180_get_all(bmp180_t *bmp180)
Get all sensor data at once.
- Parameters
bmp180 –
bmp180_tstruct to write data.- Return values
None. –
-
void bmp180_get_temperature(bmp180_t *bmp180)
Get temperature data.
- Parameters
bmp180 –
bmp180_tstruct to write data.- Return values
None. –
-
void bmp180_get_pressure(bmp180_t *bmp180)
Get pressure data.
- Parameters
bmp180 –
bmp180_tstruct to write data.- Return values
None. –
-
struct bmp180_t
- #include <bmp180.h>
Holds sensor data, sensor settings and calibration values.
Public Members
-
I2C_HandleTypeDef *hi2cx
-
float temperature
-
int32_t pressure
-
float altitude
-
int32_t sea_pressure
-
enum _bmp180_oversampling_settings oversampling_setting
-
uint8_t oss
-
int16_t AC1
-
int16_t AC2
-
int16_t AC3
-
uint16_t AC4
-
uint16_t AC5
-
uint16_t AC6
-
int16_t B1
-
int16_t B2
-
int32_t B3
-
uint32_t B4
-
int32_t B5
-
int32_t B6
-
uint32_t B7
-
int16_t MB
-
int16_t MC
-
int16_t MD
-
I2C_HandleTypeDef *hi2cx