README

PHP Package for the BMP280 temperature and barometric pressure sensor.

Contains implementations for:

BMP280

Compatible I2C Interfaces

The BMP280 communicates with your device over I2C, the InterIntegrated Circuit Protocol.

You can interface with a BMP280 with this package the following ways:

A Linux Single-Board Computer's exposed GPIO pins using the dedicated I2C SDA/SCL pins
An MPSSE-enabled USB-to-Serial device such as an FT232H generally using D0 and SCL and D1 for SDA connected to nearly any Linux or MacOS USB port.

Compatible SPI Interfaces

The BMP280 also supports SPI for direct register communication.

You can interface with a BMP280 over SPI with this package the following ways:

A Linux Single-Board Computer's exposed GPIO pins using the dedicated SPI MOSI/MISO/SCK and CS pins
An MPSSE-enabled USB-to-Serial device such as an FT232H generally using D0 and SCK, D1 for MOSI, D2 for MISO and D3 for CS connected to nearly any Linux or MacOS USB port.

Dependencies

This package makes use of modules within:

The ScrapyardIO Framework

This package also requires one of the following extensions in order to interface with I2C/SPI

In addition, an extension wrapper package is needed

For ext-posi

For ext-ftdi

Installing from Composer

Inside the root of your PHP Project, simply require the BMP package from composer

composer require dept-of-scrapyard-robotics/bmp

Framework Configuration

If you would like to use the ScrapyardIO Framework to bootstrap your sensor without wasting lines configuring your sensor right in the script you can add your desired configuration to scrapyard-io.php, such as in this example:

I2C

use DeptOfScrapyardRobotics\Sensors\BMP\BMP280;
use DeptOfScrapyardRobotics\Sensors\BMP\BMP280\Enums\BMP280I2CAddress

return [
    'boards' => [
        // For Native Configurations 
        'bmp280-native' => [
            'class_name' => BMP280::class,
            'connection' => ['driver' => 'native'],
            'startup' => [
                'i2c' => [
                    'chip_device' => 1,
                    'slave_address' => BMP280I2CAddress::SDO_GROUNDED->value,
                ],
            ],
        ],
        // For USB Configurations
        'bmp280-usb' => [
            'class_name' => BMP280::class,
            'connection' => ['driver' => 'usb'],
            'startup' => [
                'i2c' => [
                    'chip_device' => 'ft232h',
                    'slave_address' => BMP280I2CAddress::SDO_GROUNDED->value,
                ],
            ],
        ],        
    ]
];

SPI

use DeptOfScrapyardRobotics\Sensors\BMP\BMP280;
use DeptOfScrapyardRobotics\Sensors\BMP\BMP280\Enums\BMP280I2CAddress

return [
    'boards' => [
        // For Native Configurations 
        'bmp280-native' => [
            'class_name' => BMP280::class,
            'connection' => ['driver' => 'native'],
            'startup' => [
                'spi' => [
                    'master' => 0,
                    'chip_select' => 0,
                ],
            ],
        ],
        // For USB Configurations
        'bmp280-native' => [
            'class_name' => BMP280::class,
            'connection' => ['driver' => 'usb'],
            'startup' => [
                'spi' => [
                    'master' => 'ft232h',
                    'chip_select' => 0,
                ],
            ],
        ],        
    ]
];

Basic Usage

Native (POSIX) I2C driver. (Single Board Computers)

use DeptOfScrapyardRobotics\Sensors\BMP\BMP280;
use DeptOfScrapyardRobotics\Sensors\BMP\BMP280\Enums\BMP280I2CAddress

$native_i2c_sensor = BMP280::connection('native')
    ->i2c(1, BMP280I2CAddress::SDO_GROUNDED->value)
    ->create()
    
$temp_c = $native_i2c_sensor->temperature;
$rh = $native_i2c_sensor->pressure;

Native (POSIX) SPI driver. (Single Board Computers)

use DeptOfScrapyardRobotics\Sensors\BMP\BMP280;
use DeptOfScrapyardRobotics\Sensors\BMP\BMP280\Enums\BMP280I2CAddress

$native_spi_sensor = BMP280::connection('native')
    ->spi(0, 0)
    ->create()
    
$temp_c = $native_spi_sensor->temperature;
$rh = $native_spi_sensor->pressure;

USB (MPSSE) driver using I2C. (Linux and MacOS)

use DeptOfScrapyardRobotics\Sensors\BMP\BMP280;
use DeptOfScrapyardRobotics\Sensors\BMP\BMP280\Enums\BMP280I2CAddress

$usb_i2c_sensor = BMP280::connection('usb')
    ->i2c('ft232h', BMP280I2CAddress::SDO_GROUNDED->value)
    ->create()
    
$temp_c = $usb_i2c_sensor->temperature;
$rh = $usb_i2c_sensor->pressure;

USB (MPSSE) driver using SPI. (Linux and MacOS)

use DeptOfScrapyardRobotics\Sensors\BMP\BMP280;
use DeptOfScrapyardRobotics\Sensors\BMP\BMP280\Enums\BMP280I2CAddress

$usb_i2c_sensor = BMP280::connection('usb')
    ->spi('ft232h', 0)
    ->create()
    
$temp_c = $usb_i2c_sensor->temperature;
$rh = $usb_i2c_sensor->pressure;

Advanced Usage

You can tune measurement behavior at runtime using BMP280's configuration properties:

Mode controls whether reads are forced or normal.
Overscan controls precision and conversion cost for temperature/pressure.
IIR filter controls smoothing.
Standby period controls inactive time in normal mode.

use DeptOfScrapyardRobotics\Sensors\BMP\BMP280\BMP280;
use DeptOfScrapyardRobotics\Sensors\BMP\BMP280\Enums\BMP280I2CAddress;
use DeptOfScrapyardRobotics\Sensors\BMP\BMP280\Enums\BMP280IIRFilter;
use DeptOfScrapyardRobotics\Sensors\BMP\BMP280\Enums\BMP280OpMode;
use DeptOfScrapyardRobotics\Sensors\BMP\BMP280\Enums\BMP280Overscan;
use DeptOfScrapyardRobotics\Sensors\BMP\BMP280\Enums\BMP280StandbyTCS;

$sensor = BMP280::connection('native')
    ->i2c(1, BMP280I2CAddress::SDO_GROUNDED->value)
    ->create();

$sensor->mode = BMP280OpMode::NORMAL;
$sensor->overscan_temperature = BMP280Overscan::OVERSCAN_X2;
$sensor->overscan_pressure = BMP280Overscan::OVERSCAN_X16;
$sensor->iir_filter = BMP280IIRFilter::FILTER_X4;
$sensor->standby_period = BMP280StandbyTCS::STANDBY_TC_250->value;

$typical_ms = $sensor->measurement_time_typical;
$max_ms = $sensor->measurement_time_max;

Calibration

The BMP280 exposes altitude as a computed value based on local pressure and your configured sea-level pressure.

If you know the local sea-level pressure from a trusted source:

$sensor->sea_level_pressure = 1020.00;
$altitude_m = $sensor->altitude;

If you know your installation altitude and want to calibrate from it:

$sensor->altitude = 15.0;
$sea_level_pressure = $sensor->sea_level_pressure;

Notes:

pressure is reported in hPa.
altitude is reported in meters.
Readings can vary slightly because each property access may trigger a fresh conversion.

Alternative Usage

Using Through the Sensor Library (as a Temperature Sensor)

use DeptOfScrapyardRobotics\Sensors\BMP\BMP280;
use RealityInterface\Sensors\Applied\Environmental\TemperatureSensor;
use DeptOfScrapyardRobotics\Sensors\BMP\BMP280\Enums\BMP280I2CAddress;

$bmp280 = BMP280::connection('usb')
    ->i2c('ft232h', BMP280I2CAddress::SDO_GROUNDED->value)
    ->create()
    
$sensor = TemperatureSensor::as($bmp280);

$temp_c = $sensor->temperature();

$event = $sensor->measure();

Using Through the Sensor Library (as a Barometric Pressure Sensor)

use DeptOfScrapyardRobotics\Sensors\BMP\BMP280;
use DeptOfScrapyardRobotics\Sensors\BMP\BMP280\Enums\BMP280I2CAddress
use RealityInterface\Sensors\Applied\Environmental\BarometricPressureSensor;

$bmp280 = BMP280::connection('usb')
    ->i2c('ft232h', BMP280I2CAddress::SDO_GROUNDED->value)
    ->create()

$sensor = BarometricPressureSensor::as($bmp280);

$temp_c = $sensor->pressure();

$event = $sensor->measure();

Using Through the Sensor Framework (with an autoloaded config) (as a Temperature Sensor)

use RealityInterface\Sensors\Applied\Environmental\TemperatureSensor;

$sensor = TemperatureSensor::using('bmp280');

$temp_c = $sensor->temperature();

$event = $sensor->measure();

Using Through the Sensor Framework (with an autoloaded config) (as a Barometric Pressure Sensor)

use RealityInterface\Sensors\Applied\Environmental\BarometricPressureSensor;

$sensor = BarometricPressureSensor::using('bmp280');

$temp_c = $sensor->pressure();

$event = $sensor->measure();

Sensor API

The getters and setters in this API interface with the device directly (register reads/writes), so you can use property access while still working against the sensor itself.

Readable Properties (Getters)

$sensor->chip_id
Reads and returns the BMP280 chip ID.
$sensor->status
Reads and returns the status register.
$sensor->_ctrl_meas
Returns the computed control-measure register value from active settings.
$sensor->_config
Returns the computed config register value from active settings.
$sensor->config
Reads and returns the config register value from hardware.
$sensor->temperature
Reads and returns compensated temperature in Celsius.
$sensor->pressure
Reads and returns compensated pressure in hPa. Returns null if pressure overscan is disabled.
$sensor->altitude
Returns computed altitude in meters using current sea_level_pressure.
$sensor->sea_level_pressure
Returns the configured sea-level pressure in hPa.
$sensor->mode
Returns current operating mode value.
$sensor->overscan_temperature
Returns current temperature overscan value.
$sensor->overscan_pressure
Returns current pressure overscan value.
$sensor->iir_filter (BMP280IIRFilter)
Returns current IIR filter setting.
$sensor->standby_period
Returns current standby period value.
$sensor->measurement_time_typical
Returns typical conversion time in milliseconds based on active overscan settings.
$sensor->measurement_time_max
Returns maximum conversion time in milliseconds based on active overscan settings.

Writable Properties (Setters)

$sensor->altitude = 7.0;
Calibrates sea-level pressure from current pressure and the provided altitude in meters.
$sensor->sea_level_pressure = 1019.40;
Sets sea-level pressure (hPa) used by altitude calculations.
$sensor->mode = BMP280OpMode::NORMAL;
Sets operation mode (SLEEP, FORCE, NORMAL).
$sensor->overscan_temperature = BMP280Overscan::OVERSCAN_X2;
Sets temperature oversampling.
$sensor->overscan_pressure = BMP280Overscan::OVERSCAN_X16;
Sets pressure oversampling.
$sensor->iir_filter = BMP280IIRFilter::FILTER_X4;
Sets IIR filter strength.
$sensor->standby_period = BMP280StandbyTCS::STANDBY_TC_250->value;
Sets standby period in normal mode.

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