HDC2021

A driver for the Texas Instruments HDC2021 temperature and humidity sensor.

Only the basic functionality is needed - to start the sensor in one-shot mode and collect a temperature and humidity measurement.

It is compatible with the HDC2022 and HDC2080 parts, which are electrically identical.

Defines

TEMPL_REGADDR

Temperature Low register address.

TEMPH_REGADDR

Temperature High register address.

HUML_REGADDR

Humidity Low register address.

HUMH_REGADDR

Humidity High register address.

STAT_REGADDR

Status register address.

INTEN_REGADDR

Interrupt enable register address.

TEMPOFFSETADJ_REGADDR

Temperature offset adjustment register address.

HUMOFFSETADJ_REGADDR

Humidity offset adjustment register address.

DEVCONF_REGADDR

Device configuration (soft-reset and interrupt reporting) register address.

MEASCONF_REGADDR

Measurement configuration register address.

MANFIDL_REGADDR

Manufacturer ID low-byte address.

MANFIDH_REGADDR

Manufacturer ID high-byte address.

DEVIDL_REGADDR

Device ID low-byte address.

DEVIDH_REGADDR

Device ID high-byte address.

MEASCONF_MEAS_TRIG_BIT

Trigger a measurement when applied to MEASCONF_REGADDR

STAT_DRDY_STATUS_BIT

Select the DRDY_STATUS bit from STAT_REGADDR

INTEN_DRDYEN_BIT

Enable the DataReady Interrupt when applied to INTEN_REGADDR

DEVCONF_SOFT_RES_BIT

Trigger a soft reset when applied to DEVCONF_REGADDR

DEVCONF_DRDY_INTEN_BIT

Enable the DRDY/INTEN pin when applied to DEVCONF_REGADDR

Functions

int hdc2021_startconv()

Trigger a one-shot conversion.

The HDC2021 is in one-shot mode. This function sends an I2C command to trigger the temperature and humidity measurement.

It also configures the interrupt pin on HDC2021 to make a high-to-low transition when the conversion data are ready. This takes ~500us, so the MSP430 can sleep in this time to save power.

int hdc2021_init()

Initialise the HDC2021 in one-shot mode.

uint32_t hdc2021_read_temprh(int *temp12b, int *rh12b)

Read temperature and humidity from the HDC2021.

Parameters

• temp12b – [out] Pointer to a variable for storing the raw 12-bit temperature.

• rh12b – [out] Pointer to a variable for storing the raw 12-bit relative humidity.

int hdc2021_read_whoami()

Read the Device ID registers.

Returns

A 16-bit Device ID. The expected value is 0x07D0.