I'm building a library to get pressure readings from a BMP085 pressure sensor using the Wire library.
/*
BMPSensor.h - Library for reading pressure values from the BMP085
Created by Jacob Talley, September 20, 2012.
*/
#ifndef BMPSensor_h
#define BMPSensor_h
#include "Arduino.h"
#include <Wire.h>
class BMPSensor
{
public:
BMPSensor();
long ReadPressure();
private:
void bmp085Calibration();
short bmp085GetTemperature(unsigned int ut);
long bmp085GetPressure(unsigned long up);
char bmp085Read(unsigned char address);
int bmp085ReadInt(unsigned char address);
unsigned int bmp085ReadUT();
unsigned long bmp085ReadUP();
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;
};
#endif
/*
BMPSensor.cpp - Library for reading pressure values from the BMP085
Created by Jacob Talley, September 20, 2012.
*/
#include "BMPSensor.h"
#define BMP085_ADDRESS 0x77 //I2C address of BMP085
#define OSS 0 //Oversampling setting
BMPSensor::BMPSensor()
{
Wire.begin();
bmp085Calibration();
}
long BMPSensor::ReadPressure()
{
short temperature;
long pressure;
temperature = bmp085GetTemperature(bmp085ReadUT());
pressure = bmp085GetPressure(bmp085ReadUP());
return pressure;
}
void BMPSensor::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);
}
short BMPSensor::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);
}
long BMPSensor::bmp085GetPressure(unsigned long up)
{
long x1, x2, x3, b3, b6, p;
unsigned long b4, b7;
b6 = b5 - 4000;
x1 = (b2 * (b6 * b6)>>12)>>11;
x2 = (ac2 * b6)>>11;
x3 = x1 + x2;
b3 = (((((long)ac1)*4 + x3)<<OSS) + 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>>OSS));
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 p;
}
char BMPSensor::bmp085Read(unsigned char address)
{
Wire.beginTransmission(BMP085_ADDRESS);
Wire.write(address);
Wire.endTransmission();
Wire.requestFrom(BMP085_ADDRESS,1);
while(!Wire.available())
;
return Wire.read();
}
int BMPSensor::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;
}
unsigned int BMPSensor::bmp085ReadUT()
{
unsigned int ut;
Wire.beginTransmission(BMP085_ADDRESS);
Wire.write(0xF4); //register
Wire.write(0x2E); //value, requests uncompensated temp
Wire.endTransmission();
delay(5); //Wait for at least 4.5ms
ut = bmp085ReadInt(0xF6);
return ut;
}
unsigned long BMPSensor::bmp085ReadUP()
{
unsigned char msb, lsb, xlsb;
unsigned long up = 0;
Wire.beginTransmission(BMP085_ADDRESS);
Wire.write(0xF4);
Wire.write(0x34 + (OSS<<6));
Wire.endTransmission();
delay(2 + (3<<OSS)); //Wait for conversion, delay time dependant on OSS
Wire.beginTransmission(BMP085_ADDRESS);
Wire.write(0xF6);
Wire.endTransmission();
Wire.requestFrom(BMP085_ADDRESS, 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-OSS);
return up;
}
My test program is
#include <BMPSensor.h>
BMPSensor sensor;
void setup()
{
Serial.begin(9600);
}
void loop()
{
Serial.println(sensor.ReadPressure());
}
But I'm getting this error:
C:\Users\Big Bang\Documents\Arduino\libraries\BMPSensor\BMPSensor.cpp: In constructor 'BMPSensor::BMPSensor()':
C:\Users\Big Bang\Documents\Arduino\libraries\BMPSensor\BMPSensor.cpp:15: error: 'Wire' was not declared in this scope
C:\Users\Big Bang\Documents\Arduino\libraries\BMPSensor\BMPSensor.cpp: In member function 'char BMPSensor::bmp085Read(unsigned char)':
C:\Users\Big Bang\Documents\Arduino\libraries\BMPSensor\BMPSensor.cpp:89: error: 'Wire' was not declared in this scope
C:\Users\Big Bang\Documents\Arduino\libraries\BMPSensor\BMPSensor.cpp: In member function 'int BMPSensor::bmp085ReadInt(unsigned char)':
C:\Users\Big Bang\Documents\Arduino\libraries\BMPSensor\BMPSensor.cpp:104: error: 'Wire' was not declared in this scope
C:\Users\Big Bang\Documents\Arduino\libraries\BMPSensor\BMPSensor.cpp: In member function 'unsigned int BMPSensor::bmp085ReadUT()':
C:\Users\Big Bang\Documents\Arduino\libraries\BMPSensor\BMPSensor.cpp:121: error: 'Wire' was not declared in this scope
C:\Users\Big Bang\Documents\Arduino\libraries\BMPSensor\BMPSensor.cpp: In member function 'long unsigned int BMPSensor::bmp085ReadUP()':
C:\Users\Big Bang\Documents\Arduino\libraries\BMPSensor\BMPSensor.cpp:137: error: 'Wire' was not declared in this scope
Since Wire doesn't need a variable of type Wire, I'm not sure what this could be talking about.
Any ideas?