STM32 I2C Library for MS5611 temperature and pressure sensor

STM32 I2C Library for MS5611 temperature and pressure sensor

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Before going further please read MS5611 datasheet

Usage example

MS5611_Init();
MS5611_read();//get pressure and temperature takes about 10ms ToDo use non blocking mode
printf("Pressure = %f Bar Temperature = %f C\n", MS5611_Val.Pressure/100000.0, MS5611_Val.Temperature/100.0);

MS5611.h

#ifndef __MS5611_I2C_H
#define __MS5611_I2C_H

#ifdef __cplusplus
extern "C" {
#endif
#include "i2c.h"
#define OneByte                        1
#define TwoBytes                    2
#define ThreeBytes                    3
#define MS5611_I2C_ADDR                0xEC
#define CONVERSION_TIME                10 // conversion time in miliseconds
#define MS561101BA_2K                2000
#define MS561101BA_1K5                1500    
#define CMD_MS5611_RESET            0x1E
//#define CMD_MS5611_PROM_Setup        0xA0
#define CMD_MS5611_PROM_C1            0xA2
#define CMD_MS5611_PROM_C2            0xA4
#define CMD_MS5611_PROM_C3            0xA6
#define CMD_MS5611_PROM_C4            0xA8
#define CMD_MS5611_PROM_C5            0xAA
#define CMD_MS5611_PROM_C6            0xAC
//#define CMD_MS5611_PROM_CRC        0xAE
#define CMD_MS5611_PRES                0x48   // Maximum resolution (oversampling)
#define CMD_MS5611_TEMP                0x58   // Maximum resolution (oversampling)
#define FIX_TEMP                    25    
#define CONST_PF                    0.1902630958f //(1/5.25588f) Pressure factor    
    
    struct _MS5611_msg {
        int32_t Pressure;
        int32_t Temperature;
    };
    
    extern struct _MS5611_msg MS5611_Val;
    
    void MS5611_Init(void);
    void MS5611_read(void);
    //float MS5611_getAltitude(void); // in meter units
    
#ifdef __cplusplus
}
#endif

#endif /* __MS5611_I2C_H */

MS5611.c

#include "MS5611_I2C.h"
#include "i2c.h"
#include "gpio.h"
#include <math.h>

struct _MS5611_msg MS5611_Val;
uint16_t C1, C2, C3, C4, C5, C6;
//uint32_t D1, D2;
uint8_t data[3] = {0, 0, 0};
//const float sea_press = 1013.25;

static uint16_t MS5611_read_16bits(uint8_t reg)
{
    //if(HAL_I2C_Mem_Read(&hi2c1, MS5611_I2C_ADDR, reg, I2C_MEMADD_SIZE_8BIT, data, TwoBytes, I2C_TIMEOUT)!= HAL_OK)
    //    printf ("HAL_SPI_TransmitReceive \n");
    HAL_I2C_Mem_Read(&hi2c1, MS5611_I2C_ADDR, reg, I2C_MEMADD_SIZE_8BIT, data, TwoBytes, PORT_TIMEOUT);
    return ((uint16_t)data[0] << 8) | ((uint16_t)data[1] & 0xFF);
}

static void MS5611_write(uint8_t reg)
{
    //if(HAL_I2C_Master_Transmit(&hi2c1, MS5611_I2C_ADDR, &reg, OneByte, I2C_TIMEOUT) != HAL_OK)
    //    printf ("HAL_SPI_Transmit \n");
    HAL_I2C_Master_Transmit(&hi2c1, MS5611_I2C_ADDR, &reg, OneByte, PORT_TIMEOUT);
}

static uint32_t MS5611_Convert(uint8_t cmd)
{
    MS5611_write(cmd);
    HAL_Delay(CONVERSION_TIME);
    //if(HAL_I2C_Mem_Read(&hi2c1, MS5611_I2C_ADDR, 0x00, I2C_MEMADD_SIZE_8BIT, data, ThreeBytes, I2C_TIMEOUT)!= HAL_OK)
    //    printf ("HAL_SPI_TransmitReceive \n");
    HAL_I2C_Mem_Read(&hi2c1, MS5611_I2C_ADDR, 0x00, I2C_MEMADD_SIZE_8BIT, data, ThreeBytes, PORT_TIMEOUT);
    return ((uint32_t)data[0] << 16) | ((uint32_t)data[1] << 8) | ((uint32_t)data[2]);
}

void MS5611_Init(void)
{
    MS5611_write(CMD_MS5611_RESET);
    HAL_Delay(4);
    // We read the factory calibration
    // The on-chip CRC is not used
    C1 = MS5611_read_16bits(CMD_MS5611_PROM_C1);
    C2 = MS5611_read_16bits(CMD_MS5611_PROM_C2);
    C3 = MS5611_read_16bits(CMD_MS5611_PROM_C3);
    C4 = MS5611_read_16bits(CMD_MS5611_PROM_C4);
    C5 = MS5611_read_16bits(CMD_MS5611_PROM_C5);
    C6 = MS5611_read_16bits(CMD_MS5611_PROM_C6);
    //printf("C1 = %d C2 = %d C3 = %d C4 = %d C5 = %d C6 = %d\n", C1, C2, C3, C4, C5, C6);
}

void MS5611_read(void){
    int64_t dT, OFF, SENS, TEMP, T2, OFF2, SENS2, x1, x2;
    int32_t D1, D2;
    D1 = MS5611_Convert(CMD_MS5611_PRES);//raw press
    D2 = MS5611_Convert(CMD_MS5611_TEMP);// raw temp
    //printf("D1 = %d D2 = %d\n", D1, D2);
    // Difference between actual and reference temperature = D2 - Tref
    dT = D2 - ((uint64_t)C5 << 8);
    //printf("dT = %llu\n", dT);
    // Actual temperature = 2000 + dT * TEMPSENS
    TEMP = (int64_t)MS561101BA_2K + ((dT * (int64_t)C6) >> 23);
    //Offset at actual temperature
    OFF = ((uint32_t)C2 << 16) + ((dT * (int64_t)C4) >> 7);
    SENS = ((int64_t)C1 << 15) + (((int64_t)C3 * dT) >> 8);
    // Second order temperature compensation
    if (TEMP < MS561101BA_2K)
    {
        x1 = (TEMP - MS561101BA_2K);
        x2 = x1 * x1;
        T2 = ((dT * dT) >> 31);
        OFF2 = ((5 * x2) >> 1);
        SENS2 = ((5 * x2) >> 2);
        if(TEMP < -1500)
        {
            x1 = (TEMP + MS561101BA_1K5);
            x2 = x1 * x1;
            OFF2 += (7 * x2);
            SENS2 += ((11 * x2) >> 1);
        }
    }
    else
    {
        T2 = 0;
        OFF2 = 0 ;
        SENS2 = 0 ;
    }
    OFF = OFF - OFF2;
    SENS = SENS - SENS2;
    // Temperature compensated pressure = D1 * SENS - OFF
    MS5611_Val.Temperature = TEMP - T2;
    MS5611_Val.Pressure = ((((D1 * SENS) >> 21) - OFF) >> 15);
}

//float MS5611_getAltitude(void) {
//    int32_t _p, _t;
//    MS5611_read(&_p, &_t);
//    printf("P = %f mbar t = %f degC\n", _p/100.0, _t/100.0);
//    return ((pow((1015.7f / _p), CONST_PF) - 1.0f) * (FIX_TEMP + 273.15f)) / 0.0065f;
//}