라즈베리파이 BMP180 대기압 측정센서 C와 Python 코드

라즈베리파이 BMP180 대기압 측정센서 실습 : BMP180 : 고도센서, 기압센서, 온도센서 라즈베리파이 실습코드 

라즈베리파이 I2C 핀 사용법

이미지출처 : https://thepihut.com/blogs/raspberry-pi-tutorials/18025084-sensors-pressure-temperature-and-altitude-with-the-bmp180

라즈베리파이와 BMP180 대기압 측정센서 연결도 

라즈베리파이에서 $i2cdetect -y 1 명령으로 센서의 주소를 확인한다. 

파이선 코드와 C코드를 모두 아래에 나타내었다.

Python 코드는 아래를 참고한다.

#!/usr/bin/env python
 
import smbus
import time
 
MODE_ULTRALOWPOWER     = 0
MODE_STANDARD          = 1
MODE_HIGHRES           = 2
MODE_ULTRAHIGHRES      = 3
 
# BMP180의 레지스터
REGISTER_AC1 = 0xAA  
REGISTER_AC2 = 0xAC 
REGISTER_AC3 = 0xAE
REGISTER_AC4 = 0xB0
REGISTER_AC5 = 0xB2
REGISTER_AC6 = 0xB4
REGISTER_B1  = 0xB6
REGISTER_B2  = 0xB8
REGISTER_MB  = 0xBA
REGISTER_MC  = 0xBC
REGISTER_MD  = 0xBE
 
REGISTER_CONTROL           = 0xF4
REGISTER_TEMPDATA          = 0xF6
REGISTER_PRESSUREDATA      = 0xF6
 
COMMAND_READTEMP       = 0x2E
COMMAND_READPRESSURE   = 0x34
mode = MODE_STANDARD
 
# 보정 데이터 11개
AC1 = 0
AC2 = 0
AC3 = 0
AC4 = 0
AC5 = 0
AC6 = 0
B1 = 0
B2 = 0
MB = 0
MC = 0
MD = 0
 
#BMP180의 I2C 통신 주소
address = 0x77 
 
#레지스터에서 1바이트를 읽음
def read_byte(adr):
    return bus.read_byte_data(address, adr)
 
#레지스터에서 2바이트를 읽음
def read_word(adr):
    high = bus.read_byte_data(address, adr)
    low = bus.read_byte_data(address, adr+1)
    val = (high << 8) + low
    return val
 
#레지스터에서 2바이트를 읽은 후 보정함
def read_word_2c(adr):
    val = read_word(adr)
    if (val >= 0x8000):
        return -((65535 - val) + 1)
    else:
        return val
 
#레지스터에서 보정 데이터를 읽어서 저장해 둠
def init_Calibration_Data():
    global AC1, AC2, AC3, AC4, AC5, AC6, B1, B2, MB, MC, MD
    AC1 = read_word_2c(REGISTER_AC1)
    AC2 = read_word_2c(REGISTER_AC2)
    AC3 = read_word_2c(REGISTER_AC3)
    AC4 = read_word_2c(REGISTER_AC4)
    AC5 = read_word_2c(REGISTER_AC5)
    AC6 = read_word_2c(REGISTER_AC6)
    B1 = read_word_2c(REGISTER_B1)
    B2 = read_word_2c(REGISTER_B2)
    MB = read_word_2c(REGISTER_MB)
    MC = read_word_2c(REGISTER_MC)
    MD = read_word_2c(REGISTER_MD)
    print "  AC1:", AC1,"  AC2:", AC2,"  AC3:", AC3,"  AC4:", AC4,"  AC5:", AC5,"  AC6:", AC6
    print "  B1:", B1,"  B2:", B2,"  MB:", MB,"  MC:", MC,"  MD:", MD
 
 
#BMP180에서 보정전 온도 데이터를 읽음
def read_raw_Temperature():
    bus.write_byte_data(address, REGISTER_CONTROL, COMMAND_READTEMP)
    time.sleep(0.0045)  # Sleep 4.5ms
    raw = read_word_2c(REGISTER_TEMPDATA)
    print "Raw Temperature: 0x%04X (%d)" % (raw & 0xFFFF, raw)
    return raw
 
#BMP180에서 보정전 기압 데이터를 읽음
def read_raw_Pressure():
    bus.write_byte_data(address, REGISTER_CONTROL, COMMAND_READPRESSURE + (mode << 6))
    time.sleep(0.03)  # Sleep 30ms
    msb = read_byte(REGISTER_PRESSUREDATA)
    lsb = read_byte(REGISTER_PRESSUREDATA + 1)
    nxt = read_byte(REGISTER_PRESSUREDATA + 2)
    raw = ((msb << 16) + (lsb << 8) + nxt) >> (8 - mode)
    print "Raw Pressure: 0x%04X (%d)" % (raw & 0xFFFF, raw)
    return raw
 
 
#온도를 보정함
def calibrate_Temp(raw):
    UT = 0
    X1 = 0
    X2 = 0
    B5 = 0
    temp = 0.0
    X1 = ((raw - AC6) * AC5) >> 15
    X2 = (MC << 11) / (X1 + MD)
    B5 = X1 + X2
    temp = ((B5 + 8) >> 4) / 10.0
    print "Calibrated temperature = %f C" % temp
    return temp
 
 
#기압을 보정함
def calibrate_Pressure(raw):
    UT = 0
    UP = 0
    B3 = 0
    B5 = 0
    B6 = 0
    X1 = 0
    X2 = 0
    X3 = 0
    p = 0
    B4 = 0
    B7 = 0
 
    UT = read_raw_Temperature()
    UP = raw
 
    # True Temperature Calculations
    X1 = ((UT - AC6) * AC5) >> 15
    X2 = (MC << 11) / (X1 + MD)
    B5 = X1 + X2
 
    # Pressure Calculations
    B6 = B5 - 4000
    X1 = (B2 * (B6 * B6) >> 12) >> 11
    X2 = (AC2 * B6) >> 11
    X3 = X1 + X2
    B3 = (((AC1 * 4 + X3) << mode) + 2) / 4
 
    X1 = (AC3 * B6) >> 13
    X2 = (B1 * ((B6 * B6) >> 12)) >> 16
    X3 = ((X1 + X2) + 2) >> 2
    B4 = (AC4 * (X3 + 32768)) >> 15
    B7 = (UP - B3) * (50000 >> mode)
 
    if (B7 < 0x80000000):
        p = (B7 * 2) / B4
    else:
        p = (B7 / B4) * 2
 
    X1 = (p >> 8) * (p >> 8)
    X1 = (X1 * 3038) >> 16
    X2 = (-7357 * p) >> 16
 
    p = p + ((X1 + X2 + 3791) >> 4)
    print "Pressure = ", p
    return p
 
#기압을 읽은 후 보정함
def read_Pressure():
    raw = read_raw_Pressure()
    p = calibrate_Pressure(raw)
    return p
 
#온도를 읽은 후 보정함
def read_Temperature():
    raw = read_raw_Temperature()
    t = calibrate_Temp(raw)
    return t
 
 
#고도를 구함. 해수면 대기압은 값이 주어지지 않으면 표준값 사용
def read_Altitude(seaLevelPressure=101325):
    altitude = 0.0
    pressure = float(read_Pressure())
    altitude = 44330.0 * (1.0 - pow(pressure / seaLevelPressure, 0.1903))
    print "Altitude = ",  altitude
    return altitude
 
# smbus 초기화 함수. Revision2에서는 파라미터 1을 사용
bus = smbus.SMBus(1)
 
init_Calibration_Data()
temp = read_Temperature()
pressure = read_Pressure()
altitude = read_Altitude()
 
print "======== Result ======="
print "Temperature : ", temp, " C"
print "Pressure = ", pressure, "(", pressure / 100, " hPa)"
print "Altitude : ", altitude, " Meter"
 
 

C 코드는 아래를 참고한다.

#include <stdio.h>
#include <stdbool.h>
#include <signal.h>
#include <math.h>
#include <wiringPi.h>
 
#define MODE_ULTRALOWPOWER  0
#define MODE_STANDARD        1
#define MODE_HIGHRES        2
#define MODE_ULTRAHIGHRES    3 
 
// BMP180 Registers
#define REGISTER_AC1 0xAA  
#define REGISTER_AC2 0xAC 
#define REGISTER_AC3 0xAE
#define REGISTER_AC4 0xB0
#define REGISTER_AC5 0xB2
#define REGISTER_AC6 0xB4
#define REGISTER_B1  0xB6
#define REGISTER_B2  0xB8
#define REGISTER_MB  0xBA
#define REGISTER_MC  0xBC
#define REGISTER_MD  0xBE
 
#define REGISTER_CONTROL        0xF4
#define REGISTER_TEMPDATA        0xF6
#define REGISTER_PRESSUREDATA    0xF6
 
#define COMMAND_READTEMP        0x2E
#define COMMAND_READPRESSURE    0x34
 
int mode = MODE_STANDARD;
 
// Calibration data
int AC1 = 0;
int AC2 = 0;
int AC3 = 0;
int AC4 = 0;
int AC5 = 0;
int AC6 = 0;
int B1 = 0;
int B2 = 0;
int MB = 0;
int MC = 0;
int MD = 0;
 
int dID = 0x77;    // BMP180 device address
int fd = 0;    // i2c device handle
bool loop = true;
 
void my_ctrl_c_handler(int sig){ // can be called asynchronously
    close(fd);
    exit(0);
}
 
short read_word_2c(int addr)
{
    char low, high;
    short val;
    high = (char)wiringPiI2CReadReg8(fd, addr) ;
    low  = (char)wiringPiI2CReadReg8(fd, addr + 1) ;
    val = (high << 8) + low;
 
    if (val >= 0x8000)
        return -((65535 - val) + 1);
    else
        return val;
}
 
void init_Calibration_Data()
{
    AC1 = (int)read_word_2c(REGISTER_AC1);
    AC2 = (int)read_word_2c(REGISTER_AC2);
    AC3 = (int)read_word_2c(REGISTER_AC3);
    AC4 = (int)read_word_2c(REGISTER_AC4);
    AC5 = (int)read_word_2c(REGISTER_AC5);
    AC6 = (int)read_word_2c(REGISTER_AC6);
    B1 = (int)read_word_2c(REGISTER_B1);
    B2 = (int)read_word_2c(REGISTER_B2);
    MB = (int)read_word_2c(REGISTER_MB);
    MC = (int)read_word_2c(REGISTER_MC);
    MD = (int)read_word_2c(REGISTER_MD);
    printf ("  AC1:%d  AC2:%d  AC3:%d  AC4:%d  AC5:%d  AC6:%d \n", AC1, AC2, AC3, AC4, AC5, AC6);
    printf ("  B1:%d  B2:%d  MB:%d  MC:%d  MD:%d\n", B1,B2, MB, MC, MD);
}
 
int read_raw_Temperature()
{
    int raw;
    wiringPiI2CWriteReg8(fd, REGISTER_CONTROL, COMMAND_READTEMP);
    delay(5);  // Sleep 4.5ms
    raw = read_word_2c(REGISTER_TEMPDATA);
    printf ("Raw Temperature: 0x%04X (%d)\n" ,raw & 0xFFFF, raw);
    return raw;
}
 
int read_raw_Pressure()
{
    int msb, lsb, nxt;
    int raw;
    wiringPiI2CWriteReg8(fd, REGISTER_CONTROL, COMMAND_READPRESSURE + (mode << 6));
    delay(30);  // Sleep 30ms
    msb = (char)wiringPiI2CReadReg8(fd, REGISTER_PRESSUREDATA);
    lsb = (char)wiringPiI2CReadReg8(fd, REGISTER_PRESSUREDATA + 1);
    nxt = (char)wiringPiI2CReadReg8(fd, REGISTER_PRESSUREDATA + 2);
    raw = ((msb << 16) + (lsb << 8) + nxt) >> (8 - mode);
    printf( "Raw Pressure: 0x%04X (%d)\n" , raw & 0xFFFF, raw);
    return raw ;
}
 
float calibrate_Temp(int raw)
{
    int UT = 0;
    int X1 = 0;
    int X2 = 0;
    int B5 = 0;
    float temp = 0.0;
    X1 = ((raw - AC6) * AC5) >> 15;
    X2 = (MC << 11) / (X1 + MD);
    B5 = X1 + X2;
    temp = ((B5 + 8) >> 4) / 10.0;
    printf ("Calibrated temperature = %f C\n",  temp);
    return temp;
}
 
int calibrate_Pressure(int raw)
{
    int UT = 0;
    int UP = 0;
    int B3 = 0;
    int B5 = 0;
    int B6 = 0;
    int X1 = 0;
    int X2 = 0;
    int X3 = 0;
    int P = 0;
    int B4 = 0;
    int B7 = 0;
 
 
    UT = read_raw_Temperature();
    UP = raw;
 
    // True Temperature Calculations
    X1 = ((UT - AC6) * AC5) >> 15;
    X2 = (MC << 11) / (X1 + MD);
    B5 = X1 + X2;
 
    // Pressure Calculations
    B6 = B5 - 4000;
    X1 = (B2 * (B6 * B6) >> 12) >> 11;
    X2 = (AC2 * B6) >> 11;
    X3 = X1 + X2;
    B3 = (((AC1 * 4 + X3) << mode) + 2) / 4;
 
    X1 = (AC3 * B6) >> 13;
    X2 = (B1 * ((B6 * B6) >> 12)) >> 16;
    X3 = ((X1 + X2) + 2) >> 2;
    B4 = (AC4 * (X3 + 32768)) >> 15;
    B7 = (UP - B3) * (50000 >> mode);
 
    P = (B7 / B4) * 2;
 
    X1 = (P >> 8) * (P >> 8);
    X1 = (X1 * 3038) >> 16;
    X2 = (-7357 * P) >> 16;
 
    P = P + (float)((X1 + X2 + 3791) >> 4);
 
    printf( "Pressure = %f\n ", P);
    return P;
}
 
 
 
int read_Pressure()
{
    int raw;
    int p;
    raw = read_raw_Pressure();
    p = calibrate_Pressure(raw);
    return p;
}
 
float read_Temperature()
{
    int raw;
    float t;
    raw = read_raw_Temperature();
    t = calibrate_Temp(raw);
    return t;
}
 
 
float read_Altitude(int Level)
{
    float altitude = 0.0, pressure, seaLevelPressure;
    if(0 == Level) seaLevelPressure=101325.0;
    else seaLevelPressure = (float)Level;
    pressure = read_Pressure();
    altitude = 44330.0 * (1.0 - pow(pressure / seaLevelPressure, 0.1903));
    printf( "Altitude = %f\n",  altitude);
    return altitude;
}
 
int main()
{
    float temp,  altitude;
    int pressure;
    signal(SIGINT, my_ctrl_c_handler);    //Ctrl + C Handler
    
    if((fd=wiringPiI2CSetup(dID))<0){
        printf("error opening i2c channel\n\r");
        return 0;
    }
    init_Calibration_Data();
    temp = read_Temperature();
    pressure = read_Pressure();
    altitude = read_Altitude(0);
    printf( "======== Result =======\n");
    printf ("Temperature : %f C \n", temp);
    printf ("Pressure : %d Pa(%f hPa) \n", pressure, (float)pressure / 100.);
    printf ("Altitude : %f Meter \n", altitude);
    return 0;
}