I've put together this code that I use. Copy and paste it in your IDE and give it a try.
/**********************************************************
Bosch Pressure Sensor BMP085 / BMP180 readout routine
for the Arduino platform.
Compiled by Leo Nutz
www.ALTDuino.de
**********************************************************/
#include <Wire.h>
#define ADDRESS_SENSOR 0x77 // Sensor address
int16_t ac1, ac2, ac3, b1, b2, mb, mc, md; // Store sensor PROM values from BMP180
uint16_t ac4, ac5, ac6; // Store sensor PROM values from BMP180
// Ultra Low Power OSS = 0, OSD = 5ms
// Standard OSS = 1, OSD = 8ms
// High OSS = 2, OSD = 14ms
// Ultra High Resolution OSS = 3, OSD = 26ms
const uint8_t oss = 3; // Set oversampling setting
const uint8_t osd = 26; // with corresponding oversampling delay
float T, P; // Set global variables for temperature and pressure
void setup()
{
Wire.begin(); // Activate I2C
Serial.begin(9600); // Set up serial port
init_SENSOR(); // Initialize baro sensor variables
delay(100);
}
void loop()
{
int32_t b5;
b5 = temperature(); // Read and calculate temperature (T)
Serial.print("Temperature: ");
Serial.print(T, 2);
Serial.print(" C, ");
Serial.print(1.8 * T + 32.0, 2);
Serial.println(" F");
P = pressure(b5); // Read and calculate pressure (P)
Serial.print("Pressure: ");
Serial.print(P, 2);
Serial.print(" mbar, ");
Serial.print(P * 0.0295299830714, 2);
Serial.println(" inHg");
Serial.println("");
delay(500); // Delay between each readout
}
/**********************************************
Initialize sensor variables
**********************************************/
void init_SENSOR()
{
ac1 = read_2_bytes(0xAA);
ac2 = read_2_bytes(0xAC);
ac3 = read_2_bytes(0xAE);
ac4 = read_2_bytes(0xB0);
ac5 = read_2_bytes(0xB2);
ac6 = read_2_bytes(0xB4);
b1 = read_2_bytes(0xB6);
b2 = read_2_bytes(0xB8);
mb = read_2_bytes(0xBA);
mc = read_2_bytes(0xBC);
md = read_2_bytes(0xBE);
Serial.println("");
Serial.println("Sensor calibration data:");
Serial.print(F("AC1 = ")); Serial.println(ac1);
Serial.print(F("AC2 = ")); Serial.println(ac2);
Serial.print(F("AC3 = ")); Serial.println(ac3);
Serial.print(F("AC4 = ")); Serial.println(ac4);
Serial.print(F("AC5 = ")); Serial.println(ac5);
Serial.print(F("AC6 = ")); Serial.println(ac6);
Serial.print(F("B1 = ")); Serial.println(b1);
Serial.print(F("B2 = ")); Serial.println(b2);
Serial.print(F("MB = ")); Serial.println(mb);
Serial.print(F("MC = ")); Serial.println(mc);
Serial.print(F("MD = ")); Serial.println(md);
Serial.println("");
}
/**********************************************
Calcualte pressure readings
**********************************************/
float pressure(int32_t b5)
{
int32_t x1, x2, x3, b3, b6, p, UP;
uint32_t b4, b7;
UP = read_pressure(); // Read raw pressure
b6 = b5 - 4000;
x1 = (b2 * (b6 * b6 >> 12)) >> 11;
x2 = ac2 * b6 >> 11;
x3 = x1 + x2;
b3 = (((ac1 * 4 + x3) << oss) + 2) >> 2;
x1 = ac3 * b6 >> 13;
x2 = (b1 * (b6 * b6 >> 12)) >> 16;
x3 = ((x1 + x2) + 2) >> 2;
b4 = (ac4 * (uint32_t)(x3 + 32768)) >> 15;
b7 = ((uint32_t)UP - b3) * (50000 >> oss);
if(b7 < 0x80000000) { p = (b7 << 1) / b4; } else { p = (b7 / b4) << 1; } // or p = b7 < 0x80000000 ? (b7 * 2) / b4 : (b7 / b4) * 2;
x1 = (p >> 8) * (p >> 8);
x1 = (x1 * 3038) >> 16;
x2 = (-7357 * p) >> 16;
return (p + ((x1 + x2 + 3791) >> 4)) / 100.0f; // Return pressure in mbar
}
/**********************************************
Read uncompensated temperature
**********************************************/
int32_t temperature()
{
int32_t x1, x2, b5, UT;
Wire.beginTransmission(ADDRESS_SENSOR); // Start transmission to device
Wire.write(0xf4); // Sends register address
Wire.write(0x2e); // Write data
Wire.endTransmission(); // End transmission
delay(5); // Datasheet suggests 4.5 ms
UT = read_2_bytes(0xf6); // Read uncompensated TEMPERATURE value
// Calculate true temperature
x1 = (UT - (int32_t)ac6) * (int32_t)ac5 >> 15;
x2 = ((int32_t)mc << 11) / (x1 + (int32_t)md);
b5 = x1 + x2;
T = (b5 + 8) >> 4;
T = T / 10.0; // Temperature in celsius
return b5;
}
/**********************************************
Read uncompensated pressure value
**********************************************/
int32_t read_pressure()
{
int32_t value;
Wire.beginTransmission(ADDRESS_SENSOR); // Start transmission to device
Wire.write(0xf4); // Sends register address to read from
Wire.write(0x34 + (oss << 6)); // Write data
Wire.endTransmission(); // SEd transmission
delay(osd); // Oversampling setting delay
Wire.beginTransmission(ADDRESS_SENSOR);
Wire.write(0xf6); // Register to read
Wire.endTransmission();
Wire.requestFrom(ADDRESS_SENSOR, 3); // Request three bytes
if(Wire.available() >= 3)
{
value = (((int32_t)Wire.read() << 16) | ((int32_t)Wire.read() << 8) | ((int32_t)Wire.read())) >> (8 - oss);
}
return value; // Return value
}
/**********************************************
Read 1 byte from the BMP sensor
**********************************************/
uint8_t read_1_byte(uint8_t code)
{
uint8_t value;
Wire.beginTransmission(ADDRESS_SENSOR); // Start transmission to device
Wire.write(code); // Sends register address to read from
Wire.endTransmission(); // End transmission
Wire.requestFrom(ADDRESS_SENSOR, 1); // Request data for 1 byte to be read
if(Wire.available() >= 1)
{
value = Wire.read(); // Get 1 byte of data
}
return value; // Return value
}
/**********************************************
Read 2 bytes from the BMP sensor
**********************************************/
uint16_t read_2_bytes(uint8_t code)
{
uint16_t value;
Wire.beginTransmission(ADDRESS_SENSOR); // Start transmission to device
Wire.write(code); // Sends register address to read from
Wire.endTransmission(); // End transmission
Wire.requestFrom(ADDRESS_SENSOR, 2); // Request 2 bytes from device
if(Wire.available() >= 2)
{
value = (Wire.read() << 8) | Wire.read(); // Get 2 bytes of data
}
return value; // Return value
}
This is an output example:
Sensor calibration data:
AC1 = 7878
AC2 = -1089
AC3 = -14478
AC4 = 31607
AC5 = 24469
AC6 = 20562
B1 = 5498
B2 = 57
MB = -32768
MC = -11075
MD = 2432
Temperature: 23.50 C, 74.30 F
Pressure: 991.38 mbar, 29.28 inHg
Temperature: 23.50 C, 74.30 F
Pressure: 991.41 mbar, 29.28 inHg