SainSmart BMP085 Digital Pressure Sensor Module Board

// This code is based on following: https://www.sparkfun.com/tutorials/253 

#include <Wire.h> #include <LiquidCrystal.h> 

LiquidCrystal lcd(12, 11, 10, 5, 4, 3, 2);

// initialize the library with the numbers of the interface pins  

#define LOOP_MAX 100 // Max count for average 

#define BMP085_ADDRESS 0x77  // I2C address of BMP085  

const unsigned char OSS = 0;  // Oversampling Setting   

void setup() { 

  lcd.begin(16, 2); // set up the LCD's number of rows (16) and columns (2) 

  Wire.begin(); 

  bmp085Calibration(); 

} 

void loop() { 

  float temp=0,pres=0; 

  short sens_temperature; 

  long  sens_pressure; 

  int i; 

  for(i=0;i<LOOP_MAX;i++){ 

    sens_temperature = bmp085GetTemperature(bmp085ReadUT()); 

    sens_pressure = bmp085GetPressure(bmp085ReadUP()); 

    temp+=sens_temperature * 0.1; // centi degree 

    pres+=sens_pressure * 0.01; // hPa 

    delay(5); 

  } 

  temp /= LOOP_MAX; 

  pres /= LOOP_MAX; 

  // set the cursor to column 0, line 1 : 

  lcd.setCursor(0, 0); 

  // print the TEMPERATURE : 

  lcd.print("Temp="); 

  lcd.print(temp); 

  lcd.print(" C"); 

  // line 2: 

  lcd.setCursor(0, 1); 

  lcd.print("Pr="); 

  lcd.print(pres); 

  lcd.print(" hPa"); 

  delay(1000); 

} 

//////////////////////////////////////////////// 

// from BMP085 Barometric Pressure Sensor Quickstart (https://www.sparkfun.com/tutorials/253) 

// Calibration values 

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;  

// b5 is calculated in bmp085GetTemperature(...), this variable is also used in bmp085GetPressure(...) 

// so ...Temperature(...) must be called before ...Pressure(...). long b5;   

// Stores all of the bmp085's calibration values into global variables 

// Calibration values are required to calculate temp and pressure 

// This function should be called at the beginning of the program v

oid bmp085Calibration() { 

  ac1 = bmp085ReadInt(0xAA);  

  ac2 = bmp085ReadInt(0xAC); 

  ac3 = bmp085ReadInt(0xAE); 

  ac4 = bmp085ReadInt(0xB0); 

  ac5 = bmp085ReadInt(0xB2); 

  ac6 = bmp085ReadInt(0xB4); 

  b1 = bmp085ReadInt(0xB6); 

  b2 = bmp085ReadInt(0xB8); 

  mb = bmp085ReadInt(0xBA); 

  mc = bmp085ReadInt(0xBC); 

  md = bmp085ReadInt(0xBE); 

}  

// Read 1 byte from the BMP085 at 'address' 

char bmp085Read(unsigned char address) { 

  unsigned char data; 

  Wire.beginTransmission(BMP085_ADDRESS); 

  Wire.write(address); 

  Wire.endTransmission();   

  Wire.requestFrom(BMP085_ADDRESS, 1); 

  while(!Wire.available()) 

    ;  

  return Wire.read(); 

}  

// Read 2 bytes from the BMP085 

// First byte will be from 'address' 

// Second byte will be from 'address'+1 

int bmp085ReadInt(unsigned char address) { 

  unsigned char msb, lsb; 

  Wire.beginTransmission(BMP085_ADDRESS); 

  Wire.write(address); 

  Wire.endTransmission(); 

  Wire.requestFrom(BMP085_ADDRESS, 2); 

  while(Wire.available()<2) 

    ; 

  msb = Wire.read(); 

  lsb = Wire.read(); 

  return (int) msb<<8 | lsb; 

} 

// Read the uncompensated temperature value 

unsigned int bmp085ReadUT() { 

  unsigned int ut; 

  // Write 0x2E into Register 0xF4  

  // This requests a temperature reading 

  Wire.beginTransmission(BMP085_ADDRESS); 

  Wire.write(0xF4); 

  Wire.write(0x2E); 

  Wire.endTransmission(); 

  // Wait at least 4.5ms 

  delay(5); 

  // Read two bytes from registers 0xF6 and 0xF7 

  ut = bmp085ReadInt(0xF6); 

  return ut; 

}  

// Read the uncompensated pressure value 

unsigned long bmp085ReadUP() { 

  unsigned char msb, lsb, xlsb; 

  unsigned long up = 0; 

  // Write 0x34+(OSS&lt&lt6) into register 0xF4 

  // Request a pressure reading w/ oversampling setting 

  Wire.beginTransmission(BMP085_ADDRESS); 

  Wire.write(0xF4); 

  Wire.write(0x34 + (OSS<<6)); 

  Wire.endTransmission(); 

  // Wait for conversion, delay time dependent on OSS 

  delay(2 + (3<<OSS)); 

  // Read register 0xF6 (MSB), 0xF7 (LSB), and 0xF8 (XLSB) 

  Wire.beginTransmission(BMP085_ADDRESS); 

  Wire.write(0xF6); 

  Wire.endTransmission(); 

  Wire.requestFrom(BMP085_ADDRESS, 3); 

  // Wait for data to become available 

  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-OSS); 

  return up; 

}  

///////////////////////////////////////////// 

// Calculate temperature given ut. 

// Value returned will be in units of 0.1 deg C 

short bmp085GetTemperature(unsigned int ut) { 

  long x1, x2; 

  x1 = (((long)ut - (long)ac6)*(long)ac5) >> 15; 

  x2 = ((long)mc << 11)/(x1 + md); 

  b5 = x1 + x2; 

  return ((b5 + 8)>>4);   }  // Calculate pressure given up // calibration values must be known // b5 is also required so bmp085GetTemperature(...) must be called first. // Value returned will be pressure in units of Pa. long bmp085GetPressure(unsigned long up) {   long x1, x2, x3, b3, b6, p;   unsigned long b4, b7;      b6 = b5 - 4000;   // Calculate B3   x1 = (b2 * (b6 * b6)>>12)>>11;   x2 = (ac2 * b6)>>11;   x3 = x1 + x2;   b3 = (((((long)ac1)*4 + x3)<<OSS) + 2)>>2;      // Calculate B4   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>>OSS));   if (b7 &lt 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 p; }