com.raspoid.additionalcomponents

Class BarometerBMP180

java.lang.Object

com.raspoid.I2CComponent

com.raspoid.additionalcomponents.BarometerBMP180

All Implemented Interfaces:

Component

public class BarometerBMP180
extends I2CComponent

The BMP180 barometer is a digital barometric pressure sensor, with a very high performance, which enables applications in advanced mobile devices, such as smart phones, tablets and sports devices.

Use a barometer to measure air pressure and temperature.

Some specifications:

• Pressure range: 300 ... 1100hPa
• Temperature measurement included
• I2C interface
• Fully calibrated

Datasheet: BMP180

[datasheet - p.9] The pressure and temperature data has to be compensated by the callibration data of the E2PROM of the BMP180.
The BMP180 consists of a piezo-resistive sensor, an analog to digital converter and a control unit with E2PROM and a serial I2C interface. The BMP180 delivers the uncompensated value of pressure and temperature. The E2PROM has stored 176 bit of individual callibration data. This is used to compensate offset, temperature dependance and other parameters of the sensor.

• UP = pressure data (16 to 19 bit)
• UT = temperature data (16 bit)

Example of use: BarometerBMP180Example

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	BarometerBMP180.HardwarePressureAccuracyMode There exists 4 different hardware accuracy modes to deal with the BMP180 pressure measures.

Field Summary

Fields

Modifier and Type	Field and Description
static int	BMP180_ADDRESS Default i2c BMP180 address.
static int	BMP180_MSB_REG_ADDR_AC1 BMP180 register MSB address of calibration coefficient AC1.
static int	BMP180_MSB_REG_ADDR_AC2 BMP180 register MSB address of calibration coefficient AC2.
static int	BMP180_MSB_REG_ADDR_AC3 BMP180 register MSB address of calibration coefficient AC3.
static int	BMP180_MSB_REG_ADDR_AC4 BMP180 register MSB address of calibration coefficient AC4.
static int	BMP180_MSB_REG_ADDR_AC5 BMP180 register MSB address of calibration coefficient AC5.
static int	BMP180_MSB_REG_ADDR_AC6 BMP180 register MSB address of calibration coefficient AC6.
static int	BMP180_MSB_REG_ADDR_B1 BMP180 register MSB address of calibration coefficient B1.
static int	BMP180_MSB_REG_ADDR_B2 BMP180 register MSB address of calibration coefficient B2.
static int	BMP180_MSB_REG_ADDR_MB BMP180 register MSB address of calibration coefficient MB.
static int	BMP180_MSB_REG_ADDR_MC BMP180 register MSB address of calibration coefficient MC.
static int	BMP180_MSB_REG_ADDR_MD BMP180 register MSB address of calibration coefficient MD.
static int	CONTROL_PRESSURE_REQUEST Value sent to the control register to ask a new pressure value in [OUT_MSB_ADDR, OUT_LSB_ADDR, OUT_XLSB_ADDR] registers.
static int	CONTROL_REG_ADDR Control register address.
static int	CONTROL_TEMPERATURE_REQUEST Value sent to the control register to ask a new temperature value in [OUT_MSB_ADDR, OUT_LSB_ADDR] registers.
static int	OUT_LSB_ADDR Second register address containing calculated values: respectively temperature or pressure, depending on previous value sent to control register.
static int	OUT_MSB_ADDR First register address containing calculated values: respectively temperature or pressure, depending on previous value sent to control register.
static int	OUT_XLSB_ADDR Third register address containing calculated values: respectively temperature or pressure, depending on previous value sent to control register.
static double	PRESSURE_AT_SEA_LEVEL The pressure at sea level, in hPa.

Fields inherited from class com.raspoid.I2CComponent

device, MAX_I2C_ADDRESS, MIN_I2C_ADDRESS

Constructor Summary

Constructors

Constructor and Description
BarometerBMP180() Default constructor for a new barometer BMP180 using the default i2c address of the component, the ultra high resolution mode and a minimum timeout before refreshing the temperature value of 1 second.
BarometerBMP180(int i2cAddress, BarometerBMP180.HardwarePressureAccuracyMode selectedHardwarePressureAccuracyMode, int temperatureTimeout) Constructor for a new barometer BMP180 using a specific i2c address, a specific pressure accuracy mode, and a specific timeout to refresh the temperature value.

Method Summary

Modifier and Type	Method and Description
double	calculateAbsoluteAltitude() With the measured pressure p and the pressure at sea level p0, the altitude in meters can be calculated with the international barometric formula:
int	calculateTruePressure() Implements the algorithm presented in [datasheet - p.15] and returns the compensated pressure in Pa.
double	calculateTrueTemperature() Implements the algorithm pressented in [datasheet - p.15].
int	readUncompensatedPressure() Read the uncompensated pressure value from the BMP180.
int	readUncompensatedTemperature() Read the uncompensated temperature value from the BMP180.

Methods inherited from class com.raspoid.I2CComponent

getDevice, getType, readSignedRegisterValue, readTwoSignedRegsiters, readTwoUnsignedRegisters, readUnsignedRegisterValue, writeUnsignedValueDirectlyToI2CDevice, writeUnsignedValueToRegister

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

BMP180_ADDRESS

public static final int BMP180_ADDRESS

Default i2c BMP180 address.

See Also:

Constant Field Values

CONTROL_REG_ADDR

public static final int CONTROL_REG_ADDR

Control register address.

See Also:

Constant Field Values

CONTROL_TEMPERATURE_REQUEST

public static final int CONTROL_TEMPERATURE_REQUEST

Value sent to the control register to ask a new temperature value in [OUT_MSB_ADDR, OUT_LSB_ADDR] registers.

See Also:

Constant Field Values

CONTROL_PRESSURE_REQUEST

public static final int CONTROL_PRESSURE_REQUEST

Value sent to the control register to ask a new pressure value in [OUT_MSB_ADDR, OUT_LSB_ADDR, OUT_XLSB_ADDR] registers.

See Also:

Constant Field Values

OUT_MSB_ADDR

public static final int OUT_MSB_ADDR

First register address containing calculated values: respectively temperature or pressure, depending on previous value sent to control register.

See Also:

OUT_LSB_ADDR, OUT_XLSB_ADDR, Constant Field Values

OUT_LSB_ADDR

public static final int OUT_LSB_ADDR

Second register address containing calculated values: respectively temperature or pressure, depending on previous value sent to control register.

See Also:

OUT_MSB_ADDR, OUT_XLSB_ADDR, Constant Field Values

OUT_XLSB_ADDR

public static final int OUT_XLSB_ADDR

Third register address containing calculated values: respectively temperature or pressure, depending on previous value sent to control register.

See Also:

OUT_MSB_ADDR, OUT_LSB_ADDR, Constant Field Values

PRESSURE_AT_SEA_LEVEL

public static final double PRESSURE_AT_SEA_LEVEL

The pressure at sea level, in hPa.

See Also:

Constant Field Values

BMP180_MSB_REG_ADDR_AC1

public static final int BMP180_MSB_REG_ADDR_AC1

BMP180 register MSB address of calibration coefficient AC1. (1 address every 16bits (2 bytes) given that each word of data is 16bit long.)

See Also:

Constant Field Values

BMP180_MSB_REG_ADDR_AC2

public static final int BMP180_MSB_REG_ADDR_AC2

BMP180 register MSB address of calibration coefficient AC2. (1 address every 16bits (2 bytes) given that each word of data is 16bit long.)

See Also:

Constant Field Values

BMP180_MSB_REG_ADDR_AC3

public static final int BMP180_MSB_REG_ADDR_AC3

BMP180 register MSB address of calibration coefficient AC3. (1 address every 16bits (2 bytes) given that each word of data is 16bit long.)

See Also:

Constant Field Values

BMP180_MSB_REG_ADDR_AC4

public static final int BMP180_MSB_REG_ADDR_AC4

BMP180 register MSB address of calibration coefficient AC4. (1 address every 16bits (2 bytes) given that each word of data is 16bit long.)

See Also:

Constant Field Values

BMP180_MSB_REG_ADDR_AC5

public static final int BMP180_MSB_REG_ADDR_AC5

BMP180 register MSB address of calibration coefficient AC5. (1 address every 16bits (2 bytes) given that each word of data is 16bit long.)

See Also:

Constant Field Values

BMP180_MSB_REG_ADDR_AC6

public static final int BMP180_MSB_REG_ADDR_AC6

BMP180 register MSB address of calibration coefficient AC6. (1 address every 16bits (2 bytes) given that each word of data is 16bit long.)

See Also:

Constant Field Values

BMP180_MSB_REG_ADDR_B1

public static final int BMP180_MSB_REG_ADDR_B1

BMP180 register MSB address of calibration coefficient B1. (1 address every 16bits (2 bytes) given that each word of data is 16bit long.)

See Also:

Constant Field Values

BMP180_MSB_REG_ADDR_B2

public static final int BMP180_MSB_REG_ADDR_B2

BMP180 register MSB address of calibration coefficient B2. (1 address every 16bits (2 bytes) given that each word of data is 16bit long.)

See Also:

Constant Field Values

BMP180_MSB_REG_ADDR_MB

public static final int BMP180_MSB_REG_ADDR_MB

BMP180 register MSB address of calibration coefficient MB. (1 address every 16bits (2 bytes) given that each word of data is 16bit long.)

See Also:

Constant Field Values

BMP180_MSB_REG_ADDR_MC

public static final int BMP180_MSB_REG_ADDR_MC

BMP180 register MSB address of calibration coefficient MC. (1 address every 16bits (2 bytes) given that each word of data is 16bit long.)

See Also:

Constant Field Values

BMP180_MSB_REG_ADDR_MD

public static final int BMP180_MSB_REG_ADDR_MD

BMP180 register MSB address of calibration coefficient MD. (1 address every 16bits (2 bytes) given that each word of data is 16bit long.)

See Also:

Constant Field Values

Constructor Detail

BarometerBMP180

public BarometerBMP180()

Default constructor for a new barometer BMP180 using the default i2c address of the component, the ultra high resolution mode and a minimum timeout before refreshing the temperature value of 1 second.

The timeout for the temperature values here is used to don't refresh the temperature value (read on the BMP180) too frequently, as recommended by the [datasheet - p.11].

BarometerBMP180

public BarometerBMP180(int i2cAddress,
                       BarometerBMP180.HardwarePressureAccuracyMode selectedHardwarePressureAccuracyMode,
                       int temperatureTimeout)

Constructor for a new barometer BMP180 using a specific i2c address, a specific pressure accuracy mode, and a specific timeout to refresh the temperature value.

The timeout for the temperature values here is used to don't refresh the temperature value (read on the BMP180) too frequently, as recommended by the [datasheet - p.11].

Parameters:

i2cAddress - the i2c address of the BMP180 component.

selectedHardwarePressureAccuracyMode - the pressure accuracy mode.

temperatureTimeout - the minimum timeout before refreshing the temperature value, in milliseconds.

Method Detail

readUncompensatedTemperature

public int readUncompensatedTemperature()

Read the uncompensated temperature value from the BMP180.

[datasheet - p.15]

Returns:

the uncompensated temperature value from the BMP180.

readUncompensatedPressure

public int readUncompensatedPressure()

Read the uncompensated pressure value from the BMP180.

[datasheet - p.15]

Returns:

the uncompensated pressure value from the BMP180.

calculateTrueTemperature

public double calculateTrueTemperature()

Implements the algorithm pressented in [datasheet - p.15]. and returns the compensated temperature in degree celsius.

ATTENTION: the calculation of a new temperature value is limited by the b5UpdateTimeout. This is due to the fact that this value is also used with the calculateTruePressure(), and we don't need to update this value too frequenty (as recommended in the datasheet - p.11).

Returns:

the calculated compensated temperature in degree celsius.

calculateTruePressure

public int calculateTruePressure()

Implements the algorithm presented in [datasheet - p.15] and returns the compensated pressure in Pa.

Returns:

the calculated compensated pressure in Pa.

calculateAbsoluteAltitude

public double calculateAbsoluteAltitude()

With the measured pressure p and the pressure at sea level p0, the altitude in meters can be calculated with the international barometric formula:

 altitude = 44330 * (1-(p/p0)^1/5.255)
 

[datasheet - p.16]

Note: we recalculate here the calculated true pressure without any sampling rate problem. Indeed, the pressure sampling rate can increase up to 128 samples per second (in standard mode) for dynamic measurements.

Returns:

the altitude, in m, with regard to the sea level.