HTU21D Class Reference

API for the HTU21D Temperature & Humidity Sensor. More...

Detailed Description

• ID: htu21d
• Name: HTU21D Temperature & Humidity Sensor
• Category: temp
• Manufacturer: seeed adafruit sparkfun
• Link: http://www.meas-spec.com/downloads/HTU21D.pdf
• Connection: i2c

HTU21D by Measurement Specialties is a digital humidity sensor with temperature output. RH reports between 0 and 100%, and the temperature range is -40 to +125 degC. Note: getCompRH is the preferred function below (passing true to cause a measurement cycle). If actual values used for the compensated ready are necessary, use the getHumidity(false) and getTemperature(false) functions following the getCompRH call. Also note the sensor should not perform more than a couple of measurements per second to limit the heating of the sensor.

    float humidity    = 0.0;
    float temperature = 0.0;
    float compRH      = 0.0;

    sensor = new upm::HTU21D(0, HTU21D_I2C_ADDRESS);

    sensor->testSensor();

    while (!doWork) {
        compRH      = sensor->getCompRH(true);
        humidity    = sensor->getHumidity(false);
        temperature = sensor->getTemperature(false);

        std::cout << "humidity value = " <<
                    humidity <<
                    ", temperature value = " <<
                    temperature <<
                    ", compensated RH value = " <<
                    compRH << std::endl;
        usleep (500000);
    }

Public Member Functions
	HTU21D (int bus, int devAddr=HTU21D_I2C_ADDRESS)
int	sampleData (void)
float	getHumidity (int bSampleData=false)
float	getTemperature (int bSampleData=false)
float	getCompRH (int bSampleData=true)
int	setHeater (int bEnable=false)
void	resetSensor (void)
int	testSensor (void)
mraa::Result	i2cWriteReg (uint8_t reg, uint8_t value)
uint16_t	i2cReadReg_16 (int reg)
uint8_t	i2cReadReg_8 (int reg)

Constructor & Destructor Documentation

HTU21D	(	int	bus,
		int	devAddr = HTU21D_I2C_ADDRESS
	)

Instantiates an HTU21D object

Parameters

bus	Number of the used bus
devAddr	Address of the used I2C device
mode	HTU21D oversampling

Here is the call graph for this function:

Member Function Documentation

int sampleData

(

void

)

Initiates a temperature/pressure mesasurement and waits for the function to complete. The humidity and temperature registers can be read after this call.

Here is the call graph for this function:

Here is the caller graph for this function:

float getHumidity

(

int

bSampleData = false

)

Gets the current measured humidity [RH]

Here is the call graph for this function:

Here is the caller graph for this function:

float getTemperature

(

int

bSampleData = false

)

Gets the humidity cell temperature [degC]

Here is the call graph for this function:

Here is the caller graph for this function:

float getCompRH

(

int

bSampleData = true

)

Using the current humidity and temperature, the function calculates the compensated RH using the equation from the datasheet.

Here is the call graph for this function:

int setHeater

(

int

bEnable = false

)

Sets the heater state. The heater is used to test the sensor functionality since the temperature should increase 0.5 to 1.5 degC, and the humidity should decrease. The testSensor() function below uses the heater.

Parameters

bEnable

Sets to non-zero to turn the heater on

Here is the call graph for this function:

Here is the caller graph for this function:

void resetSensor

(

void

)

Performs a soft reset of the MPL3115A2 device to ensure it is in a known state. This function can be used to reset the min/max temperature and pressure values.

Here is the caller graph for this function:

int testSensor

(

void

)

Tests the device and verifies it is operating correctly.

Here is the call graph for this function:

mraa::Result i2cWriteReg	(	uint8_t	reg,
		uint8_t	value
	)

Writes to a one-byte register

Parameters

reg	Address of the register
value	Byte to be written

Here is the caller graph for this function:

uint16_t i2cReadReg_16

(

int

reg

)

Reads a two-byte register

Parameters

reg	Address of the register

Here is the caller graph for this function:

uint8_t i2cReadReg_8

(

int

reg

)

Reads a one-byte register

Parameters

reg	Address of the register

Here is the caller graph for this function:

---

The documentation for this class was generated from the following files:

• /iotdk/jenkins/workspace/upm-doc-stable/src/htu21d/htu21d.h
• /iotdk/jenkins/workspace/upm-doc-stable/src/htu21d/htu21d.cpp