.. module:: htu21d

*************
HTU21D Module
*************

This module contains the driver for MEAS HTU21D Relative Humidity and Temperature sensor.
The HTU21D is capable of direct I2C communication and can be set on 4 different level of resolution in both temperature and humidity measurements (`datasheet <http://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Data+Sheet%7FHPC199_6%7FA%7Fpdf%7FEnglish%7FENG_DS_HPC199_6_A.pdf%7FCAT-HSC0004>`_).
    
.. class:: HTU21D(i2cdrv, addr=0x40, clk=400000)

    Creates an intance of a new HTU21D.

    :param i2cdrv: I2C Bus used '( I2C0, ... )'
    :param addr: Slave address, default 0x40
    :param clk: Clock speed, default 400kHz

    Example: ::

        from meas.htu21d import htu21d

        ...

        htu = htu21d.HTU21D(I2C0)
        htu.start()
        htu.init()
        t,h = htu.get_temp_humid()

    
.. method:: init(res=0)

        Initialize the HTU21D setting the resolution of the sensor.

        :param res: set the resolution (from 0 to 3) for temperature and humidity measurements according to the table below; default 0.

========= ================ =============== ================ ===============
res value Humid Resolution Temp Resolution Meas. Time Humid Meas. Time Temp
========= ================ =============== ================ ===============
0         12 bits          14 bits         16 ms            50 ms
1         8 bits           12 bits         3 ms             13 ms
2         10 bits          13 bits         5 ms             25 ms
3         11 bits          11 bits         8 ms             7 ms
========= ================ =============== ================ ===============

        
.. method:: get_raw_temp()

        Retrieves the current temperature data from the sensor as raw value.

        Returns raw_temp

        
.. method:: get_raw_humid()

        Retrieves the current humidity data from the sensor as raw value.

        Returns raw_humid

        
.. method:: get_temp()

        Retrieves the current temperature data from the sensor as calibrate value in °C.

        Returns temp

        
.. method:: get_humid()

        Retrieves the current relative humidity data from the sensor as calibrate value in %RH.

        Returns humid

        
.. method:: get_temp_humid()

        Retrieves both temperature and humidity in one call.

        Returns temp, humid