Cảm Biến Áp Suất GY-68 BMP180

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Cảm Biến Áp Suất GY-68 BMP180:

Code mẫu Arduino với GY-68 BMP180(085):
//Arduino360.com
/*
Get pressure, altitude, and temperature from the BMP085.
Serial.print it out at 9600 baud to serial monitor.
*/

#include

#define BMP085_ADDRESS 0x77 // I2C address of BMP085

const unsigned char OSS = 0; // Oversampling Setting

// 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();

bmp085Calibration();
}

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

Serial.print(“Temperature: “);
Serial.print(temperature, 2); //display 2 decimal places
Serial.println(“deg C”);

Serial.print(“Pressure: “);
Serial.print(pressure, 0); //whole number only.
Serial.println(” Pa”);

Serial.print(“Standard Atmosphere: “);
Serial.println(atm, 4); //display 4 decimal places

Serial.print(“Altitude: “);
Serial.print(altitude, 2); //display 2 decimal places
Serial.println(” M”);

Serial.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.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<<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)
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.write(address); // send register address
Wire.write(val); // send value to write
Wire.endTransmission(); // end transmission
}

int readRegister(int deviceAddress, byte address) {

int v;
Wire.beginTransmission(deviceAddress);
Wire.write(address); // register to read
Wire.endTransmission();

Wire.requestFrom(deviceAddress, 1); // read a byte

while (!Wire.available()) {
// waiting
}

v = Wire.read();
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;
}