This is code which I'm testing
#include <Wire.h>
#define BMP085_ADDRESS 0x77 // I2C address of BMP085
int count=0;
const unsigned char OSS = 0; // Oversampling Setting
// Calibration values
const int numBMP085=3; //Number of BMP085 sensors being used, used to make array sizes
int BMPpin[numBMP085];
int ac1[numBMP085];
int ac2[numBMP085];
int ac3[numBMP085];
unsigned int ac4[numBMP085];
unsigned int ac5[numBMP085];
unsigned int ac6[numBMP085];
int b1[numBMP085];
int b2[numBMP085];
int mb[numBMP085];
int mc[numBMP085];
int md[numBMP085];
// b5 is calculated in bmp085GetTemperature(...), this variable is also used in bmp085GetPressure(...)
// so ...Temperature(...) must be called before ...Pressure(...).
long b5;
short temperature;
long pressure;
void setup()
{
Serial.begin(9600);
Wire.begin();
delay(1000);
for(int i=0;i<numBMP085;i++){
BMPpin[i]=12-i; //Set a pin number for each sensor, first is 13, 2nd is 12, etc
pinMode(BMPpin[i],OUTPUT); //Use BMPpin[0] to HIGH to turn on sensor 1, attached to pin 13
//Serial.println(BMPpin[i]);
}
for(int i=0;i<numBMP085;i++){
Serial.print("Calibrate sensor #");
Serial.println(i);
useSensor(i);
bmp085Calibration(i); //Calibrate the sensor for pin i
}
delay(500);
}
void loop()
{
if(count==numBMP085){
count=0;
}
int sensor=count; //The sensor being used will be determined by loop count,
//reset to 0 at numBMP085
useSensor(sensor);
Serial.print("Sensor #");
Serial.print(sensor);
Serial.print(": ");
delay(5);
count++;
temperature = bmp085GetTemperature(bmp085ReadUT(),sensor);
pressure = bmp085GetPressure(bmp085ReadUP(),sensor);
Serial.print("Temperature: ");
Serial.print(temperature/10.,1);
Serial.print(" deg C");
Serial.print("\tPressure: ");
Serial.print(pressure, DEC);
Serial.println(" Pa");
// Serial.println();
// delay(1000);
}
// 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
void bmp085Calibration(int sensorNum)
{
ac1[sensorNum] = bmp085ReadInt(0xAA);
ac2[sensorNum] = bmp085ReadInt(0xAC);
ac3[sensorNum] = bmp085ReadInt(0xAE);
ac4[sensorNum] = bmp085ReadInt(0xB0);
ac5[sensorNum] = bmp085ReadInt(0xB2);
ac6[sensorNum] = bmp085ReadInt(0xB4);
b1[sensorNum] = bmp085ReadInt(0xB6);
b2[sensorNum] = bmp085ReadInt(0xB8);
mb[sensorNum] = bmp085ReadInt(0xBA);
mc[sensorNum] = bmp085ReadInt(0xBC);
md[sensorNum] = bmp085ReadInt(0xBE);
/*Serial.print("Sensor number ");
Serial.println(sensorNum);
Serial.println(ac1[sensorNum]);
Serial.println(ac2[sensorNum]);
Serial.println(ac3[sensorNum]);
Serial.println(ac4[sensorNum]);
Serial.println(ac5[sensorNum]);
Serial.println(ac6[sensorNum]);
Serial.println(b1[sensorNum]);
Serial.println(b2[sensorNum]);
Serial.println(mb[sensorNum]);
Serial.println(mc[sensorNum]);
Serial.println(md[sensorNum]);*/
}
// Calculate temperature given ut.
// Value returned will be in units of 0.1 deg C
short bmp085GetTemperature(unsigned int ut, int sensor)
{
long x1, x2;
x1 = (((long)ut - (long)ac6[sensor])*(long)ac5[sensor]) >> 15;
x2 = ((long)mc[sensor] << 11)/(x1 + md[sensor]);
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,int sensor)
{
long x1, x2, x3, b3, b6, p;
unsigned long b4, b7;
b6 = b5 - 4000;
// Calculate B3
x1 = (b2[sensor] * (b6 * b6)>>12)>>11;
x2 = (ac2[sensor] * b6)>>11;
x3 = x1 + x2;
b3 = (((((long)ac1[sensor])*4 + x3)<<OSS) + 2)>>2;
// Calculate B4
x1 = (ac3[sensor] * b6)>>13;
x2 = (b1[sensor] * ((b6 * b6)>>12))>>16;
x3 = ((x1 + x2) + 2)>>2;
b4 = (ac4[sensor] * (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;
}
// 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){
Serial.print(Wire.available());
delay(100); }
;
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<<6) 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;
}
void useSensor(int sensorNum)
{
for(int i=0;i<numBMP085;i++){ //Set all pins to low, turn off all sensors
digitalWrite(BMPpin[i],LOW);
}
digitalWrite(BMPpin[sensorNum],HIGH); //Set the pin to be calibrated to high
delay(1); //<-- DON'T REMOVE THIS
//I don't know why, but without this the pressures are too high
}