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@andreuinyu andreuinyu/BMP180.ino
Last active Feb 24, 2016

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Arduino code to use with the BMP180 pressure and temperature sensor. SCL -> A5. SDA -> A4. Code worked out from the official datasheet: http://www.mouser.com/ds/2/783/BST-BMP180-DS000-12~1-786481.pdf
#include <Wire.h>
#define BMP180_I2C_Adress 0x77 //Usually 0x77
int p0 = 1013.25; //Pressure at sea level; used to calculate altitude
int i = 2; //Pressure precision setting: 0, 1, 2 or 3 (3 is broken right now. will fix.)
int AC1;
int AC2;
int AC3;
unsigned int AC4;
unsigned int AC5;
unsigned int AC6;
int b1;
int B2;
int MB;
int MC;
int MD;
long B5;
float T;
float P;
void setup(){
Wire.begin();
BMP180Calibration();
}
void loop(){
//your code here
}
int BMP180ReadInt(unsigned char adress){
unsigned char MSB, LSB;
Wire.beginTransmission(BMP180_I2C_Adress);
Wire.write(adress);
Wire.endTransmission();
Wire.requestFrom(BMP180_I2C_Adress, 2);
while (Wire.available() < 2){
Serial.print(Wire.available());
delay(100);
}
MSB = Wire.read();
LSB = Wire.read();
return (int) MSB<<8 | LSB;
}
void BMP180Calibration(){
AC1 = BMP180ReadInt(0xAA);
AC2 = BMP180ReadInt(0xAC);
AC3 = BMP180ReadInt(0xAE);
AC4 = BMP180ReadInt(0xB0);
AC5 = BMP180ReadInt(0xB2);
AC6 = BMP180ReadInt(0xB4);
b1 = BMP180ReadInt(0xB6);
B2 = BMP180ReadInt(0xB8);
MB = BMP180ReadInt(0xBA);
MC = BMP180ReadInt(0xBC);
MD = BMP180ReadInt(0xBE);
}
float BMP180Temperature(){
long X1, X2, UT;
Wire.beginTransmission(BMP180_I2C_Adress);
Wire.write(0xF4);
Wire.write(0x2E);
Wire.endTransmission();
delayMicroseconds(4500);
UT = BMP180ReadInt(0xF6);
X1 = (((long)UT - (long)AC6)*(long)AC5) >> 15;
X2 = ((long)MC << 11)/(X1 + MD);
B5 = X1 + X2;
T = ((B5 + 8)>>4);
T *= 0.1;
return T;
}
float BMP180Pressure(unsigned int precision){
long X1, X2, X3, B3, B6, p;
unsigned long B4, B7, UP;
unsigned char MSB, LSB, XLSB;
Wire.beginTransmission(BMP180_I2C_Adress);
Wire.write(0xF4);
Wire.write(0x34 + (precision<<6));
Wire.endTransmission();
if (precision == 0){
delayMicroseconds(4500);
}else if (precision == 1){
delayMicroseconds(7500);
}else if (precision == 2){
delayMicroseconds(13500);
}else if (precision == 3){
delayMicroseconds(30000);
}else{
return 0;
}
Wire.beginTransmission(BMP180_I2C_Adress);
Wire.write(0xF6);
Wire.endTransmission();
Wire.requestFrom(BMP180_I2C_Adress, 3);
while(Wire.available() < 3){
;
}
MSB = Wire.read();
LSB = Wire.read();
XLSB = Wire.read();
UP = (((unsigned long) MSB << 16) | ((unsigned long) LSB << 8) | (unsigned long) XLSB) >> (8-precision);
B6 = B5 - 4000;
X1 = (B2 * (B6 * B6)>>12)>>11;
X2 = (AC2 * B6)>>11;
X3 = X1 + X2;
B3 = (((((long)AC1)*4 + X3)<<precision) + 2)>>2;
X1 = (AC3 * B6)>>13;
X2 = (B1 * ((B6 * B6)>>12))>>16;
X3 = ((X1 + X2) + 2)>>2;
B4 = (AC4 * (unsigned long)(X3 + 32768))>>15;
B7 = ((unsigned long)(UP - B3) * (50000>>precision));
if (B7 < 0x80000000){
p = (B7<<1)/B4;
}else{
p = (B7/B4)<<1;
}
X1 = (p>>8)*(p>>8);
X1 = (X1 * 3038)>>16;
X2 = (-7357 * p)>>16;
p += (X1 + X2 + 3791)>>4;
return 0.01*p;
}
int BMP180Altitude(float p0){
return 44330*(1-pow(BMP180Pressure(i)/p0, 1/5.255));
}
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