Bosch BMP3xx module

Introduction

The BMP390 is a digital sensor with pressure and temperature measurement based on proven sensing principles. The sensor module is housed in an extremely compact 10-pin metal-lid LGA package with a footprint of only 2.0 × 2.0 mm² and max 0.8 mm package height. Its small dimensions and its low power consumption of 3.2 μA @1Hz allow the implementation in battery driven devices such as mobile phones, GPS modules or watches.

The BMP390 replaces the BMP388 and is nearly identical in specs and communication.

Although this sensor has the option of either I2C or SPI communication, this library only supports I2C. The I2C address is either 0x77 or 0x76. To connect two of these sensors to your system, you must ensure they are soldered so as to have different I2C addresses. No more than two can be attached. These sensors should be attached to a 1.7-3.6V power source and the power supply to the sensor can be stopped between measurements.

MartinL1's BMP388 library is used internally for communication with the BMP3xx. MartinL1's library was selected over the Adafruit library because it allows non-blocking operation in both normal and forced modes. It also provides many enums to help ensure correct value inputs

Bosch Recommended Oversample and Filter Settings

Sensor Datasheet

Documentation for the BMP390 sensor can be found at: https://www.bosch-sensortec.com/products/environmental-sensors/pressure-sensors/bmp390/

• BMP390 Datasheet
• BMP388 Datasheet

Build flags

• -D SEALEVELPRESSURE_HPA
  • use to adjust the sea level pressure used to calculate altitude from measured barometric pressure
  • if not defined, 1013.25 is used
  • The same sea level pressure flag is used for both the BMP3xx and the BME280. Whatever you select will be used for both sensors.

Sensor Constructors

Example Code

The BMP3xx is used in the menu a la carte example.

#include <sensors/BoschBMP3xx.h>

// NOTE: Use -1 for any pins that don't apply or aren't being used.
const int8_t bmp3xxPower = -1;  // Power pin
Mode bmpMode = FORCED_MODE;  // The operating mode of the BMP; normal or forced
Oversampling bmpPressureOversample = OVERSAMPLING_X32;
Oversampling bmpTempOversample     = OVERSAMPLING_X2;
IIRFilter    bmpFilterCoeff        = IIR_FILTER_OFF;
TimeStandby  bmpTimeStandby        = TIME_STANDBY_5MS;
uint8_t      bmpI2C_addr           = 0x77;
// The BMP3xx can be addressed either as 0x77 or 0x76

// Create a Bosch BMP3xx sensor object
BoschBMP3xx bmp3xx(bmp3xxPower, bmpMode, bmpPressureOversample,
                   bmpTempOversample, bmpFilterCoeff, bmpTimeStandby,
                   bmpI2C_addr);

// Create the variable pointers for the BMP3xx
Variable* bmp3xxTemp =
    new BoschBMP3xx_Temp(&bmp3xx, "12345678-abcd-1234-ef00-1234567890ab");
Variable* bmp3xxPress =
    new BoschBMP3xx_Pressure(&bmp3xx, "12345678-abcd-1234-ef00-1234567890ab");
Variable* bmp3xxAlt =
    new BoschBMP3xx_Altitude(&bmp3xx, "12345678-abcd-1234-ef00-1234567890ab");

Classes

class BoschBMP3xx

The Sensor sub-class for the Bosch BMP3xx.

class BoschBMP3xx_Temp

The Variable sub-class used for the temperature output from a Bosch BMP3xx.

class BoschBMP3xx_Pressure

The Variable sub-class used for the atmospheric pressure output from a Bosch BMP3xx.

class BoschBMP3xx_Altitude

The Variable sub-class used for the altitude calculated from the measurements made by a Bosch BMP3xx.

Defines

#define BMP3XX_NUM_VARIABLES = 3

Sensor::_numReturnedValues; the BMP3xx can report 3 values.

#define BMP3XX_INC_CALC_VARIABLES = 1

Sensor::_incCalcValues; altitude is calculted within the Adafruit library.

#define SEALEVELPRESSURE_HPA = (1013.25)

The atmospheric pressure at sea level.

Sensor Timing

The sensor timing for a Bosch BMP3xx

#define BMP3XX_WARM_UP_TIME_MS = 3

Sensor::_warmUpTime_ms; BMP3xx should be ready to communicate within 3ms.

Time to first communication after both V_DD > 1.8 V and V_DDIO > 1.8 V is 2ms (max) for the BMP390. Power-on time from stand-by mode is 3 ms (max) for the BMP390. I don't understand why it takes longer to be ready from stand-by than from power off, but we'll use the larger number.

#define BMP3XX_STABILIZATION_TIME_MS = 4000

Sensor::_stabilizationTime_ms; BMP3xx is stable after 4000ms.

0.5 s for good numbers, but optimal at 4 s based on tests using bmp3xxtimingTest.ino

#define BMP3XX_MEASUREMENT_TIME_MS = 80

Sensor::_measurementTime_ms; The number given in this define will be recalculated and over-written in the set-up.

The BMP390 takes 78.09ms (max) to complete a measurement at 32x pressure oversampling and 2x temperature oversampling. A measurement may take up to 138ms at 32x pressure and temperature oversampling, but oversampling rates above 2x for temperature are not recommended.

Following 3.9.2 of the datasheet:

In both forced mode and normal mode the pressure and temperature measurement duration follow the equation:

With:

• = total conversion time in μs
• = "0" or "1", depending of the status of the press_en bit
• = "0" or "1", depending of the status of the temp_en bit
• = amount of pressure oversampling repetitions
• = amount of temperature oversampling repetitions

Further, based on table 23 in the datasheet, there is up to a 18% difference between the "typical" measurement time (as given by the equation) and the maximum measurement time.

ModularSensors will always enable both pressure and temperature measurement and add an extra 18% wait to the calculated measurement time.

Temperature

The temperature variable from a Bosch BMP388 or BMP390

• Range is -40°C to +85°C
  • Full accuracy between 0°C and +65°C
• Absolute accuracy is typ. ± 0.5°C at 25°C
  • ± 1.5°C over 0°C to +65°C range

#define BMP3XX_TEMP_RESOLUTION = 2

Decimals places in string representation; temperature should have 5 - resolution is 0.0.00015°C at the hightest oversampling. See table 7 in the sensor datasheet for resolution at all bandwidths.

#define BMP3XX_TEMP_VAR_NUM = 0

Sensor variable number; temperature is stored in sensorValues[0].

#define BMP3XX_TEMP_VAR_NAME = "temperature"

Variable name in ODM2 controlled vocabulary; "temperature".

#define BMP3XX_TEMP_UNIT_NAME = "degreeCelsius"

Variable unit name in ODM2 controlled vocabulary; "degreeCelsius" (°C)

#define BMP3XX_TEMP_DEFAULT_CODE = "BoschBMP3xxTemp"

Default variable short code; "BoschBMP3xxTemp".

Barometric Pressure

The barometric pressure variable from a Bosch BMP388 or BMP390

• Range for both the BMP388 and BMP390 is 300‒1250 hPa
• Absolute accuracy is typ. ± 50 Pa (±0.50 hPa)
• Relative accuracy is typ. ± 3 Pa (±0.03 hPa), equiv. to ± 0.25 m

#define BMP3XX_PRESSURE_RESOLUTION = 3

Decimals places in string representation; barometric pressure should have 3. Resolution of output data in highest resolution mode at lowest bandwidth is 0.016 Pa. See table 6 in the sensor datasheet for resolution at all bandwidths.

#define BMP3XX_PRESSURE_VAR_NUM = 1

Sensor variable number; pressure is stored in sensorValues[2].

#define BMP3XX_PRESSURE_VAR_NAME = "barometricPressure"

Variable name in ODM2 controlled vocabulary; "barometricPressure".

#define BMP3XX_PRESSURE_UNIT_NAME = "pascal"

Variable unit name in ODM2 controlled vocabulary; "pascal" (Pa)

#define BMP3XX_PRESSURE_DEFAULT_CODE = "BoschBMP3xxPressure"

Default variable short code; "BoschBMP3xxPressure".

Altitude

The altitude variable from a Bosch BMP388 or BMP390

#define BMP3XX_ALTITUDE_RESOLUTION = 0

Decimals places in string representation; altitude should have 0 - resolution is 1m.

#define BMP3XX_ALTITUDE_VAR_NUM = 2

Sensor variable number; altitude is stored in sensorValues[3].

#define BMP3XX_ALTITUDE_VAR_NAME = "heightAboveSeaFloor"

Variable name in ODM2 controlled vocabulary; "heightAboveSeaFloor".

#define BMP3XX_ALTITUDE_UNIT_NAME = "meter"

Variable unit name in ODM2 controlled vocabulary; "meter".

#define BMP3XX_ALTITUDE_DEFAULT_CODE = "BoschBMP3xxAltitude"

Default variable short code; "BoschBMP3xxAltitude".