BMP180 C library using STM32 I2C HAL driver

bmp180.c

/*
 * bmp180.c
 *
 *  Created on: 27 feb. 2019
 *      Author: gheorghe.ghirjev
 */

#include <string.h>
#include <math.h>
#include "bmp180.h"
#include "stm32f7xx_hal.h"


// global struct to store all BMP180 main data.
bmp_t bmp;

extern I2C_HandleTypeDef hi2c1;



/*!
* @brief:    - Read and check bmp chip ID.This value is fixed to 0x55,
*              and can be used to check whether communication is functioning.
* @param[in] - NONE.
* @return    - NO_ERR if chip_id is equal to 0x55, otherwise CHIP_ID_INVALID_ERR.
*/
static bmp_err_t read_chip_id (void)
{
	uint8_t out_buff = 0;
	uint8_t ret_val = NO_ERR;

	HAL_I2C_Mem_Read(&hi2c1, BMP_READ_ADDR, BMP_CHIP_ID_REG, 1, &out_buff, 1, BMP_I2C_TIMEOUT);

	if (BMP_CHIP_ID_VAL != out_buff)
	{
		ret_val = CHIP_ID_INVALID_ERR;
	}

	return ret_val;
}


/*!
* @brief:    - Write oversampling settings to the Control register.
* @param[in] - struct of type oss_t
* @param[in] - enum of type oss_ratio_t
* @return    - None
*/
static void set_oss (oss_t * oss, oss_ratio_t ratio)
{
	uint8_t in_buff[2] = {0};

	switch (ratio)
	{
		case ULTRA_LOW_PWR_MODE:
		{
			oss->wait_time = BMP_OSS0_CONV_TIME;
			break;
		}
		case STANDARD_MODE:
		{
			oss->wait_time = BMP_OSS1_CONV_TIME;
			break;
		}
		case HIGH:
		{
			oss->wait_time = BMP_OSS2_CONV_TIME;
			break;
		}
		case ULTRA_HIGH_RESOLUTION:
		{
			oss->wait_time = BMP_OSS3_CONV_TIME;
			break;
		}
		default:
		{
			oss->wait_time = BMP_OSS1_CONV_TIME;
			break;
		}
	}

	oss->ratio = ratio;
	BMP_SET_I2CRW_REG (in_buff[1], BMP_CTRL_OSS_MASK(ratio));
	HAL_I2C_Mem_Write( &hi2c1, BMP_WRITE_ADDR, BMP_CTRL_REG, 1, in_buff, 2, BMP_I2C_TIMEOUT );
}


/*!
* @brief:    - Read calibration BMP data. The E2PROM has stored 176 bit of individual calibration data.
*              This is used to compensate offset, temperature dependence and other parameters of the sensor.
* @param[in] - struct of type bmp_calib_param_t
* @return    - NO_ERR if read calibration data are valid otherwise READ_CALIB_ERR.
*/
static bmp_err_t read_calib_data (short * calib_data)
{
	bmp_err_t ret_val = NO_ERR;
	uint8_t out_buff[BMP_CALIB_DATA_SIZE] = {0};
	uint8_t i = 0;
	uint8_t j = 1;

	HAL_I2C_Mem_Read(&hi2c1, BMP_READ_ADDR, BMP_CALIB_ADDR, 1, out_buff, BMP_CALIB_DATA_SIZE, BMP_I2C_TIMEOUT);

	// Store read calib data to bmp_calib struct.
	for (i = 0; i <= BMP_CALIB_DATA_SIZE / 2; i++, j+2)
	{
		calib_data[i] = (out_buff[i * 2] << 8) | out_buff[j];

		// checking that none of the words has the value 0 or 0xFFFF.
		if ((0 == calib_data[i]) | (-1 == calib_data[i]))
		{
			ret_val = GET_CALIB_ERR;
		}
	}

	return ret_val;
}

/*!
* @brief:    - Performe initial sequence of BMP sensor
* @param[in] - pointer to struct of type bmp_calib_param_t
* @return    - None.
*/
void bmp_init (bmp_t * bmp)
{
	memset(bmp, 0x00, sizeof(&bmp)); // clear bmp strut;
	bmp->err = read_chip_id ();      // check chip validity and I2C communication.
	bmp->err = read_calib_data ((short *)&bmp->calib);
	set_oss (&bmp->oss, HIGH);       // set oversampling settings
}

/*!
* @brief:    - Get uncompensated temperature value. UT = temperature data (16 bit)
* @param[in] - None.
* @return    - uncompensated temp.
*/
int32_t get_ut (void)
{
	uint8_t out_buff[2];

	BMP_SET_I2CRW_REG (out_buff[0], BMP_SET_TEMP_CONV);
	HAL_I2C_Mem_Write( &hi2c1, BMP_WRITE_ADDR, BMP_CTRL_REG, 1, out_buff, 1, BMP_I2C_TIMEOUT );
	HAL_Delay (BMP_TEMP_CONV_TIME);
	HAL_I2C_Mem_Read ( &hi2c1, BMP_READ_ADDR, BMP_DATA_MSB_ADDR, 1, out_buff, 2, BMP_I2C_TIMEOUT );

	return (out_buff[0] << BYTE_SHIFT) | out_buff[1];
}

/*!
* @brief:    - Calc true temperature.
* @param[in] - pointer to struct of type bmp_t
* @return    - true temp.
*/
float get_temp(bmp_t * bmp)
{
	int32_t X1 = 0;
	int32_t X2 = 0;
	float temp = 0;

	X1 = (((int32_t)bmp->uncomp.temp - bmp->calib.AC6) * bmp->calib.AC5) >> 15;
	X2 = (bmp->calib.MC << 11) / (X1 + bmp->calib.MD);
	bmp->data.B5 = X1 + X2;
	temp = ((bmp->data.B5 + 8) >> 4) * 0.1f;

	if ((temp <= BMP_MIN_TEMP_THRESHOLD) || (temp >= BMP_MAX_TEMP_THRESHOLD))
	{
		bmp->err = GET_TEMP_ERR;
	}

	return temp;
}

/*!
* @brief:    - Get uncompensated pressure value. UP = pressure data (16 to 19 bit)
* @param[in] - struct of type oss_t
* @return    - uncompensated pressure.
*/
int32_t get_up (oss_t oss)
{
	uint8_t out_buff[3] = {0};
	long up = 0;

	BMP_SET_I2CRW_REG (out_buff[0], BMP_SET_PRESS_CONV);
	HAL_I2C_Mem_Write ( &hi2c1, BMP_WRITE_ADDR, BMP_CTRL_REG, 1, out_buff, 1, BMP_I2C_TIMEOUT );
	HAL_Delay (oss.wait_time);
	HAL_I2C_Mem_Read(&hi2c1, BMP_READ_ADDR, BMP_DATA_MSB_ADDR, 1, out_buff, 3, BMP_I2C_TIMEOUT);

	up = ((out_buff[0] << SHORT_SHIFT) + (out_buff[1] << BYTE_SHIFT) + out_buff[2]) >> (8 - oss.ratio);
	return up;
}

/*!
* @brief:    - Calc true pressure.
* @param[in] - struct of type bmp_t
* @return    - true pressure in Pa.
*/
int32_t get_pressure(bmp_t bmp)
{
	int32_t X1, X2, X3, B3, B6, p = 0;
	uint32_t B4, B7 = 0;

	B6 = bmp.data.B5 - 4000;
	X1 = (bmp.calib.B2 * (B6 * B6 / 0x1000)) / 0x800;
	X2 = bmp.calib.AC2 * B6 / 0x800;
	X3 = X1 + X2;
	B3 = (((bmp.calib.AC1 * 4 + X3) << bmp.oss.ratio) +2) / 4;
	X1 = bmp.calib.AC3 * B6 / 0x2000;
	X2 = (bmp.calib.B1 * (B6 * B6 / 0x1000)) / 0x10000;
	X3 = ((X1 + X2) + 2) / 0x4;
	B4 = bmp.calib.AC4 * (unsigned long)(X3 + 32768) / 0x8000;
	B7 = ((unsigned long)bmp.uncomp.press - B3) * (50000 >> bmp.oss.ratio);

	if (B7 < 0x80000000)
	{
		p = (B7 * 2) / B4;
	}
	else
	{
		p = (B7 / B4) * 2;
	}

	X1 = (p / 0x100 * (p / 0x100));
	X1 = (X1 * 3038) / 0x10000;
	X2 = (-7357 * p) / 0x10000;
	p = p + (X1 + X2 + 3791) / 0x10;

	return p;
}

/*!
* @brief:    - Calc true altitude.
* @param[in] - struct of type bmp_t
* @return    - true pressure.
*/
float get_altitude (bmp_t * bmp)
{
	float altitude = 0;

	altitude = BMP_PRESS_CONST_COEFICIENT * (1.0f - pow((bmp->data.press / BMP_PRESS_CONST_SEA_LEVEL), (1/5.255)));

	if ((altitude <= BMP_MIN_ALT_THRESHOLD) || (altitude >= BMP_MAX_ALT_THRESHOLD))
	{
		bmp->err = GET_ALTITUDE_ERR;
	}

	return altitude;
}

bmp180.h

/*
 * bmp180.h
 *
 *  Created on: 27 feb. 2019
 *      Author: gheorghe.ghirjev
 */

#ifndef BMP180_H_
#define BMP180_H_


#include "stdint.h"


// Data type definitions:
#define BYTE_SHIFT					(8U)
#define SHORT_SHIFT					(16U)

/* Chip-id [R/O] (register D0h): This value is fixed to 0x55,
 * and can be used to check whether communication is functioning. */
#define BMP_CHIP_ID_REG			      		(0xD0)
#define BMP_CHIP_ID_VAL					(0x55)

/* Measurement control [R/W] (register F4h):
 * <4:0> - Controls measurements.
 * <5>   - SCO : Start of conversion. The value of this bit stays “1” during conversion,
 *               and is reset to “0” after conversion is complete
 * <7:6> - OSS : Controls the oversampling ratio of the pressure measurement
 */
#define BMP_CTRL_REG	         	       		(0xF4)
#define BMP_CTRL_SCO_BIT(reg)				((reg & 0x20) >> 5)
#define BMP_CTRL_OSS_MASK(oss)				(oss = (oss & 0x3) << 6)

#define BMP_OSS0_CONV_TIME				(5U)
#define BMP_OSS1_CONV_TIME				(8U)
#define BMP_OSS2_CONV_TIME				(14U)
#define BMP_OSS3_CONV_TIME				(26U)

/* Soft reset [W/O] (register E0h):
 * If set to 0xB6, will perform the same sequence as power on reset. */
#define BMP_SOFT_RST_REG 	                	(0xE0)
#define BMP_SOFT_RST_VAL  	                	(0xB6)

// Calibration data [R/O] (register AAh up to BFh):
#define BMP_CALIB_ADDR  	                	(0xAA)
#define BMP_CALIB_DATA_SIZE				(22U)

// Device I2C addr register [R/O]: write EEh, read EFh:
#define BMP_READ_ADDR	                    		(0xEF)
#define BMP_WRITE_ADDR		                	(0xEE)
#define BMP_I2C_TIMEOUT					(50U)
#define BMP_SET_I2CRW_REG(i2c_buff, reg)		(i2c_buff = reg)

// BMP measurmenet regs
#define BMP_DATA_MSB_ADDR	                	(0xF6)
#define BMP_DATA_LSB_ADDR	                	(0xF7)
#define BMP_DATA_XLSB_ADDR	                	(0xF8)

// Temp. measurement :
#define BMP_SET_TEMP_CONV		            	(0x2E)

#define BMP_TEMP_CONV_TIME				(5U)
#define BMP_MIN_TEMP_THRESHOLD				(-40)
#define BMP_MAX_TEMP_THRESHOLD				(85U)

// Pressure measurment :
#define BMP_SET_PRESS_CONV		            	(0x34)
#define BMP_PRESS_CONST_SEA_LEVEL 	    		(101325.0f) // pressure in Pa
#define BMP_PRESS_CONST_COEFICIENT 	    		(44330.0f)

// Altitude measurment :
#define BMP_MIN_ALT_THRESHOLD				(-500)	// m. relating to sea level)
#define BMP_MAX_ALT_THRESHOLD				(9000U)	// m. relating to sea level)



struct bmp_calib_param_t
{
	int16_t	 AC1;
	int16_t  AC2;
	int16_t  AC3;
	uint16_t AC4;
	uint16_t AC5;
	uint16_t AC6;
	int16_t  B1;
	int16_t  B2;
	int16_t  MB;
	int16_t  MC;
	int16_t  MD;
};

struct measure_data_t
{
	float temp;
	int32_t press;
	/* for uncompensated values do not use below fields: */
	int32_t B5;
	float altitude;
};

typedef enum
{
	ULTRA_LOW_PWR_MODE = 0,
	STANDARD_MODE,
	HIGH,
	ULTRA_HIGH_RESOLUTION
} oss_ratio_t;

typedef struct
{
	oss_ratio_t ratio;
	uint8_t wait_time;
}oss_t;

typedef enum
{
	NO_ERR = 0,
	CHIP_ID_INVALID_ERR,
	GET_CALIB_ERR,
	GET_TEMP_ERR,
	GET_PRESSURE_ERR,
	GET_ALTITUDE_ERR
} bmp_err_t;

typedef struct
{
	struct bmp_calib_param_t calib;
	struct measure_data_t uncomp;	// uncompensated values
	struct measure_data_t data;
	oss_t oss;
	bmp_err_t err;
}bmp_t;



/*!
* @brief:    - Performe initial sequence of BMP180 sensor.
* @param[in] - pointer to struct of type bmp_calib_param_t
* @return    - None.
*/
void bmp_init (bmp_t * bmp);

/*!
* @brief:    - Read oversampling settings from CTRL reg F4h.
* 			   Oss (register F4h <7:6>): controls the oversampling ratio of the pressure measurement
* 			   (00b: single, 01b: 2 times, 10b: 4 times, 11b: 8 times).
* @param[in] - None.
* @return    - None.
*/
static void set_oss (oss_t * oss, oss_ratio_t ratio);

/*!
* @brief:    - Get uncompensated temperature value.
* @param[in] - None.
* @return    - uncompensated temp.
*/
int32_t get_ut (void);

/*!
* @brief:    - Calc true temperature.
* @param[in] - pointer to struct of type bmp_t
* @return    - true temp.
*/
float get_temp(bmp_t * bmp);

/*!
* @brief:    - Get uncompensated pressure value.
* @param[in] - oss - conversion time.
* @return    - uncompensated pressure.
*/
int32_t get_up (oss_t oss);

/*!
* @brief:    - Calc true pressure.
* @param[in] - struct of type bmp_t
* @return    - true pressure in Pa.
*/
int32_t get_pressure(bmp_t bmp);

/*!
* @brief:    - Calc true altitude.
* @param[in] - struct of type bmp_t
* @return    - altitude in meters.
*/
float get_altitude (bmp_t * bmp);

#endif /* BMP180_H_ */

C library for BMP180 digital pressure sensor, link
Tis library is destinated for Cortex M7 MCU Hardware, to use it on another ARM Cortex board change the inclusion
#include "stm32f7xx_hal.h" in bmp180.c to needed stm32fX header.

The following code is the API calling in your main function :
bmp_t bmp;

main () {
bmp_init (&bmp);
while (1) {
bmp.uncomp.temp = get_ut ();
bmp.data.temp = get_temp (&bmp);
bmp.uncomp.press = get_up (bmp.oss);
bmp.data.press = get_pressure (bmp);
bmp.data.altitude = get_altitude (&bmp);
}

Hello, I'm grateful for the library that was created,
but after I compailer an error occurred.

error lies when I initialize
bmp_init (& bmp);
'bmp' undeclared (first use in this function); did you mean 'bmp_t'?

Hello.
First of all, thank you very much for all the material you provided.
I have been trying to make it work on a STM32H747 board, which is double core.
I download the program on the CM4 core which is suitable for my application. The problem is that when I try to read the values, temperature stands on 0 °C and Pressure on 236.
It is very strange becouse when I make the reading of uncompensated values I can see the oscilating on time.
The I2C comunication is working by the way.
I don't know if you have any more specific example so you can provided it.
I would really apreciate that.

Thank you very much in advance.

Hello, I'm grateful for the library that was created,
but after I compailer an error occurred.

error lies when I initialize
bmp_init (& bmp);
'bmp' undeclared (first use in this function); did you mean 'bmp_t'?

you must add definition of "bmp" at main.c

bmp_t bmp;

main () {
bmp_init (&bmp);
while (1) {
bmp.uncomp.temp = get_ut ();
bmp.data.temp = get_temp (&bmp);
bmp.uncomp.press = get_up (bmp.oss);
bmp.data.press = get_pressure (bmp);
bmp.data.altitude = get_altitude (&bmp);
}

Hello

Sorry for missing "bmp_t bmp;" declaration in main.c file
Thanks @inflamerzt for helping with missing line. I've updated description comment !

Best Regards