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June 25, 2012 05:44
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//Arduino 1.0+ Only | |
//Arduino 1.0+ Only | |
/*Based largely on code by Jim Lindblom | |
Get pressure, altitude, and temperature from the BMP085. | |
Serial.print it out at 9600 baud to serial monitor. | |
*/ | |
#include <Wire.h> | |
#include <LiquidCrystal.h> | |
#define BMP085_ADDRESS 0x77 // I2C address of BMP085 | |
const unsigned char OSS = 0; // Oversampling Setting | |
LiquidCrystal lcd(7, 8, 9, 10, 11, 12); | |
// 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; | |
void setup(){ | |
//Serial.begin(9600); | |
Wire.begin(); | |
lcd.begin(16, 2); | |
bmp085Calibration(); | |
lcd.setCursor(0,0); | |
lcd.print("BMP085Test"); | |
delay(5000); | |
lcd.clear(); | |
} | |
void loop() | |
{ | |
float temperature = bmp085GetTemperature(bmp085ReadUT()); //MUST be called first | |
float pressure = bmp085GetPressure(bmp085ReadUP()); | |
//float atm = pressure / 101325; // "standard atmosphere" | |
//float altitude = calcAltitude(pressure); //Uncompensated caculation - in Meters | |
lcd.setCursor(0,0); | |
lcd.print("Temp: "); | |
lcd.setCursor(0,1); | |
float fahrenheit; | |
fahrenheit=(((9.0 / 5.0) * temperature) + 32.0); | |
lcd.print(fahrenheit, 0); //display 2 decimal places | |
//lcd.println("deg C"); | |
lcd.setCursor(8,0); | |
lcd.print("Press: "); | |
lcd.setCursor(8,1); | |
float inpress; | |
inpress=(pressure*0.000295299830714); | |
lcd.print(inpress, 2); //whole number only. | |
//lcd.println(" Pa"); | |
//lcd.print("Standard Atmosphere: "); | |
//lcd.println(atm, 4); //display 4 decimal places | |
//lcd.print("Altitude: "); | |
//lcd.print(altitude, 2); //display 2 decimal places | |
//lcd.println(" M"); | |
//lcd.println();//line break | |
delay(1000); //wait a second and get values again. | |
} | |
// 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() | |
{ | |
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); | |
} | |
// Calculate temperature in deg C | |
float bmp085GetTemperature(unsigned int ut){ | |
long x1, x2; | |
x1 = (((long)ut - (long)ac6)*(long)ac5) >> 15; | |
x2 = ((long)mc << 11)/(x1 + md); | |
b5 = x1 + x2; | |
float temp = ((b5 + 8)>>4); | |
temp = temp /10; | |
return temp; | |
} | |
// 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 < 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; | |
long temp = p; | |
return temp; | |
} | |
// Read 1 byte from the BMP085 at 'address' | |
char bmp085Read(unsigned char address) | |
{ | |
unsigned char data; | |
Wire.beginTransmission(BMP085_ADDRESS); | |
Wire.send(address); | |
Wire.endTransmission(); | |
Wire.requestFrom(BMP085_ADDRESS, 1); | |
while(!Wire.available()) | |
; | |
return Wire.receive(); | |
} | |
// 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.send(address); | |
Wire.endTransmission(); | |
Wire.requestFrom(BMP085_ADDRESS, 2); | |
while(Wire.available()<2) | |
; | |
msb = Wire.receive(); | |
lsb = Wire.receive(); | |
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.send(0xF4); | |
Wire.send(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.send(0xF4); | |
Wire.send(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) | |
msb = bmp085Read(0xF6); | |
lsb = bmp085Read(0xF7); | |
xlsb = bmp085Read(0xF8); | |
up = (((unsigned long) msb << 16) | ((unsigned long) lsb << 8) | (unsigned long) xlsb) >> (8-OSS); | |
return up; | |
} | |
void writeRegister(int deviceAddress, byte address, byte val) { | |
Wire.beginTransmission(deviceAddress); // start transmission to device | |
Wire.send(address); // send register address | |
Wire.send(val); // send value to write | |
Wire.endTransmission(); // end transmission | |
} | |
int readRegister(int deviceAddress, byte address){ | |
int v; | |
Wire.beginTransmission(deviceAddress); | |
Wire.send(address); // register to read | |
Wire.endTransmission(); | |
Wire.requestFrom(deviceAddress, 1); // read a byte | |
while(!Wire.available()) { | |
// waiting | |
} | |
v = Wire.receive(); | |
return v; | |
} | |
//float calcAltitude(float pressure){ | |
//float A = pressure/101325; | |
//float B = 1/5.25588; | |
//float C = pow(A,B); | |
//C = 1 - C; | |
//C = C /0.0000225577; | |
//return C; | |
//} |
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