An Arduino compatible, non-blocking, I2C/SPI library for the Bosch BMP280 barometer.

© Copyright, image courtesy of Adafruit Industries lisensed under the terms of the Create Commons Attribution-ShareAlike 3.0 Unported.

This BMP280_DEV library offers the following features:

• Returns temperature in degrees celius (°C), pressure in hectoPascals/millibar (hPa) and altitude in metres (m)
• NORMAL or FORCED modes of operation
• I2C or hardware SPI communications with configurable clock rates
• Non-blocking operation
• In NORMAL mode barometer returns results at the specified standby time interval
• Highly configurable, allows for changes to pressure and temperature oversampling, IIR filter and standby time

• Version 1.0.6 -- Merged multiple instances and initialisation pull requests by sensslen
• Version 1.0.5 -- Fixed bug in BMP280_DEV::getTemperature() function, thanks to Jon M.
• Version 1.0.3 -- Change library name in the library.properties file
• Version 1.0.2 -- Modification to allow external creation of a HSPI object on the ESP32
• Version 1.0.1 -- Added ESP32 HSPI support and changed library name for Arduino compatibility
• Version 1.0.0 -- Intial version

• All Arduino boards, but for 5V Arduino boards (such as the Uno, Nano, Mega, Leonardo, etc...), please check if the BMP280 breakout board requires a 5V to +3.3V voltage level shifter

After download simply un-zip the file and place the BMP280 directory in your .../Arduino/libraries/... folder. The .../Arduino/... folder is the one where your Arduino IDE sketches are usually located.

Simply include the BMP280_DEV.h file at the beginning of your sketch:

#include <BMP280_DEV.h>

For I2C communication the BMP280_DEV object is created (instantiated) without parameters:

BMP280_DEV bmp280;	// Set up I2C communications

By default the library uses the BMP280's I2C address 0x77. (To use the alternate I2C address: 0x76, see the begin() function below.

For SPI communication the chip select (CS) Arduino digital output pin is specified as an argument, for example digital pin 10:

BMP280_dev bmp280(10);	// Set up SPI communications on digital pin D10

The library also supports the ESP32 HSPI operation on pins: SCK 14, MOSI 13, MISO 27 and user defined SS (CS):

SPIClass SPI1(HSPI);							// Create the SPI1 HSPI object
BMP280_DEV bmp(21, HSPI, SPI1);		// Set up HSPI port communications on the ESP32

By default the I2C runs in fast mode at 400kHz and SPI at 1MHz.

To initialise the bmp280 it is necessary to call the begin() function with or without parameters. The parameters specify the starting mode, pressure/temperature oversampling, IIR filter and standby time options respectively:

bmp280.begin(SLEEP_MODE, OVERSAMPLING_X16, OVERSAMPLING_X2, IIR_FILTER_4, TIME_STANDBY_05MS);

Alternatively simply call the begin function without any paremeters, this sets up the default configuration: SLEEP_MODE, pressure oversampling X16, temperature oversampling X2, IIR filter OFF and a standby time of 0.5ms:

bmp280.begin();	// Initialise the BMP280 with default configuration

Another alternative is to pass the BMP280's mode as an argument:

bmp280.begin(NORMAL_MODE);	// Initialise the BMP280 in NORMAL_MODE with default configuration

Or, specifying mode and alternate I2C address:

bmp280.begin(FORCED_MODE, BMP280_I2C_ALT_ADDR);	// Initialise the BMP280 in FORCED_MODE with the alternate I2C address (0x76)

Or even just the alternate I2C address, (BMP280 initialised in SLEEP_MODE by default):

bmp280.begin(BMP280_I2C_ALT_ADDR);	// Initialise the BMP280 with the alternate I2C address (0x76)

Note that the begin functions return the value 1 upon successful initialisation, otherwise it returns 0 for failure.

After initialisation it is possible to change the BMP280 configuration with the following functions:

bmp280.setPresOversamping(OVERSAMPING_X4);	// Options are OVERSAMPLING_SKIP, _X1, _X2, _X4, _X8, _X16

bmp280.setTempOversamping(OVERSAMPING_X4);	// Options are OVERSAMPLING_SKIP, _X1, _X2, _X4, _X8, _X16

bmp280.setIIRFilter(IIR_FILTER_16);	// Options are IIR_FILTER_OFF, _2, _4, _8, _16

bmp280.setTimeStandby(TIME_STANDBY_2000MS);	// Options are TIME_STANDBY_05MS, _62MS, _125MS, _250MS, _500MS, _1000MS, 2000MS, 4000MS

The BMP280 has 3 modes of operation: SLEEP_MODE, NORMAL_MODE and FORCED_MODE:

• SLEEP_MODE: puts the device into an inactive standby state

• NORMAL_MODE: performs continuous conversions, separated by the standby time

• FORCED_MODE: performs a single conversion, returning to SLEEP_MODE upon completion

To kick-off conversions in NORMAL_MODE:

bmp280.startNormalConversion();	// Start continuous conversions, separated by the standby time

To perform a single oneshot conversion in FORCED_MODE:

bmp280.startForcedConversion();	// Start a single oneshot conversion

To stop the conversion at anytime and return to SLEEP_MODE:

bmp280.stopConversion();	// Stop conversion and return to SLEEP_MODE

The BMP280 barometer library acquires temperature in degrees celius (°C), pressure in hectoPascals/millibar (hPa) and altitude in metres (m). The acquisition functions scan the BMP280's status register and return 1 if the barometer results are ready and have been successfully read, 0 if they are not; this allows for non-blocking code implementation. The temperature, pressure and altitude results themselves are float variables by passed reference to the function and are updated upon a successful read.

Here are the results acquisition functions:

bmp280.getMeasurements(temperature, pressure, altitude);	// Acquire temperature, pressue and altitude measurements

bmp280.getTempPres(temperature, pressure);	// Acquire both the temperature and pressure

bmp280.getTemperature(temperature);	// Acquire the temperature only

bmp280.getPressure(pressure);	// Acquire the pressure only, (also calculates temperature, but doesn't return it)

bmp280.getAltitude(altitude);	// Acquire the altitude only

Here is an example sketch of how to use the BMP280 library for non-blocking I2C operation, default configuration with continuous conversion in NORMAL_MODE, but with a standby sampling time of 1 second:

#include <BMP280_DEV.h>                           // Include the BMP280_DEV.h library

float temperature, pressure, altitude;            // Create the temperature, pressure and altitude variables
BMP280_DEV bmp280;                                // Instantiate (create) a BMP280_DEV object and set-up for I2C operation (address 0x77)

void setup() 
{
  Serial.begin(115200);                           // Initialise the serial port
  bmp280.begin();                                 // Default initialisation, place the BMP280 into SLEEP_MODE 
  bmp280.setTimeStandby(TIME_STANDBY_1000MS);     // Set the standby time to 1s
  bmp280.startNormalConversion();                 // Start NORMAL conversion mode
}

void loop() 
{
  if (bmp280.getMeasurements(temperature, pressure, altitude))    // Check if the measurement is complete
  {
    Serial.print(temperature);                    // Display the results    
    Serial.print(F("*C   "));
    Serial.print(pressure);    
    Serial.print(F("hPa   "));
    Serial.print(altitude);
    Serial.println(F(m"));
  }
}

A second sketch example for I2C operation, default configuration in FORCED conversion mode:

#include <BMP280_DEV.h>                           // Include the BMP280_DEV.h library

float temperature, pressure, altitude;            // Create the temperature, pressure and altitude variables
BMP280_DEV bmp280;                                // Instantiate (create) a BMP280_DEV object and set-up for I2C operation (address 0x77)

void setup() 
{
  Serial.begin(115200);                           // Initialise the serial port
  bmp280.begin();                                 // Default initialisation, place the BMP280 into SLEEP_MODE 
}

void loop() 
{
  bmp280.startForcedConversion();                 // Start a forced conversion (if in SLEEP_MODE)
  if (bmp280.getMeasurements(temperature, pressure, altitude))    // Check if the measurement is complete
  {
    Serial.print(temperature);                    // Display the results    
    Serial.print(F("*C   "));
    Serial.print(pressure);    
    Serial.print(F("hPa   "));
    Serial.print(altitude);
    Serial.println(F("m"));
  }
}

The sketches for SPI operation are identical except that the line:

BMP280_DEV bmp280;	// Instantiate (create) a BMP280_DEV object and set-up for I2C operation (address 0x77)

...should be replaced with the line:

BMP280_DEV bmp280(10);	// Instantiate (create) a BMP280_DEV object and set-up for SPI operation with chip select on D10

For more details see code examples provided in the .../examples/... directory.

I2C Normal Mode: sampling at 2 seconds standby time intervals with default settings

I2C Normal Mode (Alterntive I2C Address): sampling at 2 second standby time intervals with default settings

I2C Forced Mode: with default settings

SPI Normal Mode: sampling at 2 second standby time intervals with default settings

SPI Forced Mode: with default settings

ESP32 HSPI Normal Mode: sampling at 1 second standby time intervals with default settings