# BME280
Provides an Arduino library for reading and interpreting Bosch BME280 data.

## Table of Contents

* [BME280](#bme280)
* [Table of Contents](#table_of_contents)
* [Summary](#summary)
* [Installation](#installation)
* [Usage](#usage)
* [Methods](#methods)

 * [BME280(uint8_t tosr = 0x1, uint8_t hosr = 0x1, uint8_t posr = 0x1, uint8_t mode = 0x3, uint8_t st = 0x5, uint8_t filter = 0x0, bool spiEnable = false, uint8_t bme_280_addr = 0x76)](#methods)
 * [bool  begin()](#methods)
 * [void  setMode(uint8_t mode)](#methods)
 * [float temp(bool celsius = true)](#methods)
 * [float pres(uint8_t unit = 0x0)](#methods)
 * [float hum()](#methods)
 * [void  data(float& pressure, float& temp, float& humidity, bool metric = true, uint8_t p_unit = 0x0)](#methods)
 * [float alt(bool metric = true, float seaLevelPressure = 101325)](#methods)
 * [float alt(float pressure, bool metric = true, float seaLevelPressure = 101325)](#methods)
 * [float dew(bool metric = true)](#methods)
 * [float dew(float temp, float hum, bool metric = true)](#methods)
* [Contributing](#contributing)
* [History](#history)
* [Credits](#credits)
* [License](#license)
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## Summary

Reads temperature, humidity, and pressure. Calculates altitude and dew point. Provides functions for english and metric. Also reads pressure in Pa, hPa, inHg, atm, bar, torr, N/m^2 and psi.

## Installation

To use this library download the zip file, uncompress it to a folder named BME280. Move the folder to {Arduino Path}/libraries.

## Usage

Include the library at the top of your Arduino script. `#include <BME280>`
Create a global or local variable. `BME280 bme`
In your start up call `bme.begin()`.
Read the temperature, humidity, pressure, altitude and/or dew point.

`float pres, temp, hum`
`bme.data(pres, temp, hum)`

or

`temp = bme.temp()`
`hum = bme.hum()`
`pres = bme.pres()`

`float altitude, dewPoint`
`altitude = bme.alt()`
`dewPoint = bme.dew()`

Use `setMode(0x01)` to trigger a new measurement in forced mode. NOTE: It takes ~8ms to measure all values (temp, humidity & pressure) when using x1 oversampling (see datasheet 11.1). Thus a delay of >8ms should be used after triggering a measurement and before reading data to ensure that read values are the latest ones.

## Methods


#### BME280(uint8_t tosr = 0x1, uint8_t hosr = 0x1, uint8_t posr = 0x1, uint8_t mode = 0x3, uint8_t st = 0x5, uint8_t filter = 0x0, bool spiEnable = false, uint8_t bme_280_addr = 0x76)

  Constructor used to create the class. All parameters have default values.
  Return: None

    * Temperature Oversampling Rate (tosr): uint8_t, default = 0x1
      values: B000 = Skipped, B001 = x1, B010 = x2, B011 = x4, B100 = x8, B101/other = x16

    * Humidity Oversampling Rate (hosr): uint8_t, default = 0x1
      values: B000 = Skipped, B001 = x1, B010 = x2, B011 = x4, B100 = x8, B101/other = x16

    * Pressure Oversampling Rate (posr): uint8_t, default = 0x1
      values: B000 = Skipped, B001 = x1, B010 = x2, B011 = x4, B100 = x8, B101/other = x16

    * Mode: uint8_t, default = Normal
      values: Sleep = B00, Forced = B01 and B10, Normal = B11

    * Standby Time (st): uint8_t, default = 1000ms
      values: B000 = 0.5ms, B001 = 62.5ms, B010 = 125ms, B011 = 250ms, B100 = 250ms, B101 = 1000ms, B110 = 10ms, B111 = 20ms

    * Filter: uint8_t, default = None
      values: B000 = off, B001 = 2, B010 = 4, B011 = 8, B100/other = 16

    * SPI Enable: bool, default = false
      values: true = enable, false = disable

    * BME280 Address: uint8_t, default = 0x76
      values: any uint8_t




#### bool  begin()

  Method used at start up to initialize the class. Starts the I2C interface.
  Return: bool, true = success, false = failure (no device found)

#### void setMode(uint8_t mode)

  Method to set the sensor mode. Sleep = B00, Forced = B01 and B10, Normal = B11. Set to B01 to trigger a new measurement when using forced mode.

#### float temp(bool celsius = true)

  Read the temperature from the BME280 and return a float.
  Return: float = temperature

    * Celsius: bool, default = true
      values: true = return temperature in degrees Celsius, false = return
      temperature in degrees Fahrenheit


#### float pres(uint8_t unit = 0x0)

  Read the pressure from the BME280 and return a float with the specified unit.
  Return: float = pressure

    * Unit: uint8_t, default = 0x0
      values: B000 = Pa, B001 = hPa, B010 = Hg, B011 = atm, B100 = bar,
      B101 = torr, B110 = N/m^2, B111 = psi

#### float hum()

  Read the humidity from the BME280 and return a percentage as a float.
  Return: float = percent relative humidity

#### void  data(float& pressure, float& temp, float& humidity, bool metric = true, uint8_t p_unit = 0x0)

  Read the data from the BME280 with the specified units.
  Return: None, however, pressure, temp and humidity are changed.

    * Pressure: float, reference
      values: reference to storage float for pressure

    * Temperature: float, reference
      values: reference to storage float for temperature

    * Humidity: float, reference
      values: reference to storage float for humidity

    * Metric: bool, default = true
      values: true = meters, false = feet

    * Pressure Unit: uint8_t, default = 0x0
        values: B000 = Pa, B001 = hPa, B010 = Hg, B011 = atm, B100 = bar,
        B101 = torr, B110 = N/m^2, B111 = psi

#### float alt(bool metric = true, float seaLevelPressure = 101325)

  Read the data from the BME280 with the specified units and then calculate the altitude.
  Return: float = altitude

    * Metric: bool, default = true
      values: true = meters, false = feet

    * Sea Level Pressure: float, unit = Pa, default = 101325
      values:  any float


#### float alt(float pressure, bool metric = true, float seaLevelPressure = 101325)

  Calculate the altitude based on the pressure with the specified units.
  Return: float = altitude

    * Pressure: float, unit = Pa
      values: any float

    * Metric: bool, default = true
      values: true = meters, false = feet

    * Sea Level Pressure: float, unit = Pa, default = 101325
      values:  any float

#### float dew(bool metric = true)

  Read BME280 data and calculate the dew point with the specified units.
  Return: float = dew point

    * Metric: bool, default = true
      values: true = return temperature in degrees Celsius, false = return
      temperature in degrees Fahrenheit

#### float dew(float temp, float hum, bool metric = true)

  Calculate the dew point based on the temperature and humidity with the specified units.
  Return: float = dew point

    * Temperature: float, unit = Celsius if metric is true, Fahrenheit if metric is false
      values: any float

    * Humidity: float, unit = % relative humidity
      values: any float

    * Metric: bool, default = true
      values: true = return degrees Celsius, false = return degrees Fahrenheit

## Contributing

1. Fork the project.
2. Create your feature branch: `git checkout -b my-new-feature`
3. Commit your changes: `git commit -am 'Add some feature'`
4. Push to the branch: `git push origin my-new-feature`
5. Submit a pull request.

## History

Jan 1, 2016 - Version 1.0.0 released.
Sep 19, 2016 - Version 2.0.0 released (support for I2C and SPI).

## Credits

Written by Tyler Glenn, 2016.

Special thanks to Mike Glenn for editing and reviewing the code.

## License

GNU GPL, see License.txt
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