C++ API for HTU21D chip (Atmospheric Pressure 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

Measurement Specialties [HTU21D] is a digital humidity sensor with temperature output. RH will report between 0 and 100% and temperature range is -40 to +125 degC. Note that the getCompRH is the preferred function below (passing true to cause a measurement cycle). If the actual values used for the compensated ready are necessary, use the getHumidity(false) and getTemperature(false) functions following the getCompRH call. Also note that 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)

	~HTU21D ()

int	sampleData (void)

float	getHumidity (int bSampleData=false)

float	getTemperature (int bSampleData=false)

float	getCompRH (int bSampleData=true)

int	setHeater (int bEnable=false)

int	resetSensor (void)

int	testSensor (void)

mraa_result_t	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`
	)

Instanciates a HTU21D object

Parameters

bus	number of used bus
devAddr	address of used i2c device
mode	HTU21D oversampling

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~HTU21D ( )

HTU21D object destructor, basicaly it close i2c connection.

Member Function Documentation

int sampleData ( void )

Initiate a temp/pressure mesasurement and wait for function to complete. The humidity and temp registers can be read after this call.

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float getHumidity ( int bSampleData = false )

Get the current measured humidity [RH]

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float getTemperature ( int bSampleData = false )

Get the humidity cell temperature [degC]

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float getCompRH ( int bSampleData = true )

Using the current humidity and temperature the function will calculate the compensated RH using the equation from the datasheet.

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int setHeater ( int bEnable = false )

Set the heater state. The heater is used to either test the sensor functionality since the temp should increase 0.5 to 1.5 degC and the humidity should decrease. The testSensor() function below will use the heater.

Parameters

bEnable Set to non-zero to turn on heater

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int resetSensor ( void )

Perform 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.

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