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MePressureSensor.cpp
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MePressureSensor.cpp
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#include "MePressureSensor.h"
MePressureSensor::MePressureSensor() {
}
boolean MePressureSensor::begin(uint8_t mode) {
if (mode > BMP180_ULTRAHIGHRES)
mode = BMP180_ULTRAHIGHRES;
oversampling = mode;
Wire.begin();
if (readUInt8(0xD0) != 0x55) return false;
ac1 = readUInt16(BMP180_CAL_AC1);
ac2 = readUInt16(BMP180_CAL_AC2);
ac3 = readUInt16(BMP180_CAL_AC3);
ac4 = readUInt16(BMP180_CAL_AC4);
ac5 = readUInt16(BMP180_CAL_AC5);
ac6 = readUInt16(BMP180_CAL_AC6);
b1 = readUInt16(BMP180_CAL_B1);
b2 = readUInt16(BMP180_CAL_B2);
mb = readUInt16(BMP180_CAL_MB);
mc = readUInt16(BMP180_CAL_MC);
md = readUInt16(BMP180_CAL_MD);
return true;
}
int32_t MePressureSensor::computeB5(int32_t UT) {
int32_t X1 = (UT - (int32_t)ac6) * ((int32_t)ac5) >> 15;
int32_t X2 = ((int32_t)mc << 11) / (X1+(int32_t)md);
return X1 + X2;
}
uint16_t MePressureSensor::readRawTemperature(void) {
writeUInt8(BMP180_CONTROL, BMP180_READTEMPCMD);
delay(5);
return readUInt16(BMP180_TEMPDATA);
}
uint32_t MePressureSensor::readRawPressure(void) {
uint32_t raw;
writeUInt8(BMP180_CONTROL, BMP180_READPRESSURECMD + (oversampling << 6));
if (oversampling == BMP180_ULTRALOWPOWER)
delay(5);
else if (oversampling == BMP180_STANDARD)
delay(8);
else if (oversampling == BMP180_HIGHRES)
delay(14);
else
delay(26);
raw = readUInt16(BMP180_PRESSUREDATA);
raw <<= 8;
raw |= readUInt8(BMP180_PRESSUREDATA+2);
raw >>= (8 - oversampling);
return raw;
}
int32_t MePressureSensor::readPressure(void) {
int32_t UT, UP, B3, B5, B6, X1, X2, X3, p;
uint32_t B4, B7;
UT = readRawTemperature();
UP = readRawPressure();
B5 = computeB5(UT);
B6 = B5 - 4000;
X1 = ((int32_t)b2 * ( (B6 * B6)>>12 )) >> 11;
X2 = ((int32_t)ac2 * B6) >> 11;
X3 = X1 + X2;
B3 = ((((int32_t)ac1*4 + X3) << oversampling) + 2) / 4;
X1 = ((int32_t)ac3 * B6) >> 13;
X2 = ((int32_t)b1 * ((B6 * B6) >> 12)) >> 16;
X3 = ((X1 + X2) + 2) >> 2;
B4 = ((uint32_t)ac4 * (uint32_t)(X3 + 32768)) >> 15;
B7 = ((uint32_t)UP - B3) * (uint32_t)( 50000UL >> oversampling );
if (B7 < 0x80000000) {
p = (B7 * 2) / B4;
} else {
p = (B7 / B4) * 2;
}
X1 = (p >> 8) * (p >> 8);
X1 = (X1 * 3038) >> 16;
X2 = (-7357 * p) >> 16;
p = p + ((X1 + X2 + (int32_t)3791)>>4);
return p;
}
int32_t MePressureSensor::readSealevelPressure(float altitude_meters) {
float pressure = readPressure();
return (int32_t)(pressure / pow(1.0-altitude_meters/44330, 5.255));
}
float MePressureSensor::readTemperature(void) {
int32_t UT, B5;
float temp;
UT = readRawTemperature();
B5 = computeB5(UT);
temp = (B5+8) >> 4;
temp /= 10;
return temp;
}
float MePressureSensor::readAltitude(float sealevelPressure) {
float altitude;
float pressure = readPressure();
altitude = 44330 * (1.0 - pow(pressure /sealevelPressure,0.1903));
return altitude;
}
uint8_t MePressureSensor::readUInt8(uint8_t a) {
uint8_t ret;
Wire.beginTransmission(BMP180_I2CADDR);
#if (ARDUINO >= 100)
Wire.write(a);
#else
Wire.send(a);
#endif
Wire.endTransmission();
Wire.beginTransmission(BMP180_I2CADDR);
Wire.requestFrom(BMP180_I2CADDR, 1);
#if (ARDUINO >= 100)
ret = Wire.read();
#else
ret = Wire.receive();
#endif
Wire.endTransmission();
return ret;
}
uint16_t MePressureSensor::readUInt16(uint8_t a) {
uint16_t ret;
Wire.beginTransmission(BMP180_I2CADDR);
#if (ARDUINO >= 100)
Wire.write(a);
#else
Wire.send(a);
#endif
Wire.endTransmission();
Wire.beginTransmission(BMP180_I2CADDR);
Wire.requestFrom(BMP180_I2CADDR, 2);
#if (ARDUINO >= 100)
ret = Wire.read();
ret <<= 8;
ret |= Wire.read();
#else
ret = Wire.receive();
ret <<= 8;
ret |= Wire.receive();
#endif
Wire.endTransmission();
return ret;
}
void MePressureSensor::writeUInt8(uint8_t a, uint8_t d) {
Wire.beginTransmission(BMP180_I2CADDR);
#if (ARDUINO >= 100)
Wire.write(a);
Wire.write(d);
#else
Wire.send(a);
Wire.send(d);
#endif
Wire.endTransmission();
}