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EVNEnvSensor

EVNEnvSensor#

This class provides the following features and functionalities for our Environment Sensor Standard Peripheral (BME280 IC):

  • Temperature, Humidity & Pressure Measurements

  • Altitude Calculation (based on pressure measurement & local sea-level pressure)

  • Non-Blocking & Blocking Read Functions

Note

This class does I2C port selection automatically, so users do not need to call setPort() using their EVNAlpha objects.

Wiring (I2C)#

Host

Peripheral

Description

3V3

VIN

3.3V Power

GND

GND

Ground (0V)

SCL

SCL

I2C Serial Clock

SDA

SDA

I2C Serial Data

–

CSB

Not Connected

–

SDO

Not Connected

Constructor#

class EVNEnvSensor(uint8_t port, sampling sampling_temp = ENV_SAMPLING_X1, sampling sampling_pres = ENV_SAMPLING_X1, sampling sampling_hum = ENV_SAMPLING_X1, filter filter = ENV_FILTER_OFF, standby standby = ENV_STANDBY_MS_0_5)#
Parameters

  • port – I2C port the sensor is connected to (1-16)

  • sampling_temp – Sampling rate for temperature. Defaults to ENV_SAMPLING_X1

  • sampling_pres – Sampling rate for pressure. Defaults to ENV_SAMPLING_X1

  • sampling_hum – Sampling rate for humidity. Defaults to ENV_SAMPLING_X1

  • filter – Filter rate applied to readings. Defaults to ENV_FILTER_OFF

  • standby – Standby time between end of reading and start of new reading (in ms). Defaults to ENV_STANDBY_MS_0_5

Functions#

bool begin()

Initializes environment sensor. Call this function before using the other functions.

Returns

Boolean indicating whether the sensor was successfully initialized. If false is returned, all other functions will return 0.

Note

If begin() returns false, try checking your connections and I2C port number!

void setSeaLevelPressure(float pressure)

Set sea-level pressure used to calculate altitude

Param

pressure (in Pa)

void setTemperatureOffset(float offset)

Set offset applied to temperature readings. E.g. offset of 3 increases all temperature readings by 3 deg Celsius

Param

offset (in deg C)

Reading Temperature#

float readTemp(bool blocking = true)
float readTemperature(bool blocking = true)
float readTemperatureC(bool blocking = true)

Read temperature (in Celsius)

Parameters

blocking – Block function from returning a value until a new reading is obtained. Defaults to true

Returns

temperature (in deg C)

float readTemperatureF(bool blocking = true)

Read temperature (in Fahrenheit)

Parameters

blocking – Block function from returning a value until a new reading is obtained. Defaults to true

Returns

temperature (in deg F)

Reading Humidity#

float readHum(bool blocking = true)
float readHumidity(bool blocking = true)

Read humidity (from 0-100%)

Parameters

blocking – Block function from returning a value until a new reading is obtained. Defaults to true

Returns

humidity (0-100)

Reading Pressure & Altitude#

float readPres(bool blocking = true)
float readPressure(bool blocking = true)

Read pressure in Pascals

Parameters

blocking – Block function from returning a value until a new reading is obtained. Defaults to true

Returns

altitude (in Pa)

float readAltitude(bool blocking = true)
float readAltitudeMetres(bool blocking = true)

Read altitude in metres

Parameters

blocking – Block function from returning a value until a new reading is obtained. Defaults to true

Returns

altitude (in m)

float readAltitudeFeet(bool blocking = true)

Read altitude in feet

Parameters

blocking – Block function from returning a value until a new reading is obtained. Defaults to true

Returns

altitude (in ft)

Advanced Sensor Settings#

void setMode(bool enable)

Sets mode to run sensor in

Parameters

enable – Whether measurement is enabled

void setSamplingRate(sampling sampling_temp, sampling sampling_hum, sampling sampling_pres)

Sets sampling rate for each of the 3 measurements. Increasing sampling rate lowers variance at the cost of response time.

Additionally, note that temperature measurement cannot be disabled.

Parameters

  • sampling_temp – Sampling rate for temperature

  • sampling_pres – Sampling rate for pressure

  • sampling_hum – Sampling rate for humidity

  • ENV_SAMPLING_OFF (disables measurement)

  • ENV_SAMPLING_X1 (1)

  • ENV_SAMPLING_X2 (2)

  • ENV_SAMPLING_X4 (4)

  • ENV_SAMPLING_X8 (8)

  • ENV_SAMPLING_X16 (16)

void setFilterRate(filter filter)

Sets filter rate applied to pressure measurements. Increasing filter rate lowers variance at the cost of response time.

Parameters

filter – Filter rate for pressure measurements

  • ENV_FILTER_OFF (filter disabled)

  • ENV_FILTER_X2 (2)

  • ENV_FILTER_X4 (4)

  • ENV_FILTER_X8 (8)

  • ENV_FILTER_X16 (16)

void setStandbyTime(standby standby_time)

Sets standby time between end of reading and start of new reading (in ms)

Parameters

standby_time – Standby time between readings

  • ENV_STANDBY_MS_0_5 (0.5ms)

  • ENV_STANDBY_MS_10 (10ms)

  • ENV_STANDBY_MS_20 (20ms)

  • ENV_STANDBY_MS_62_5 (62.5ms)

  • ENV_STANDBY_MS_125 (125ms)

  • ENV_STANDBY_MS_250 (250ms)

  • ENV_STANDBY_MS_500 (500ms)

  • ENV_STANDBY_MS_1000 (1000ms)

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