Kernel driver htu21
===================

Supported chips:
  * Measurement Specialties HTU21D
    Prefix: 'htu21'
    Addresses scanned: none
    Datasheet: Publicly available at the Measurement Specialties website
    http://www.meas-spec.com/downloads/HTU21D.pdf


Author:
  William Markezana <william.markezana@meas-spec.com>

Description
-----------

The HTU21D is a humidity and temperature sensor in a DFN package of
only 3 x 3 mm footprint and 0.9 mm height.

The devices communicate with the I2C protocol. All sensors are set to the
same I2C address 0x40, so an entry with I2C_BOARD_INFO("htu21", 0x40) can
be used in the board setup code.

This driver does not auto-detect devices. You will have to instantiate the
devices explicitly. Please see Documentation/i2c/instantiating-devices
for details.

sysfs-Interface
---------------

temp1_input - temperature input
humidity1_input - humidity input

Notes
-----

The driver uses the default resolution settings of 12 bit for humidity and 14
bit for temperature, which results in typical measurement times of 11 ms for
humidity and 44 ms for temperature. To keep self heating below 0.1 degree
Celsius, the device should not be active for more than 10% of the time. For
this reason, the driver performs no more than two measurements per second and
reports cached information if polled more frequently.

Different resolutions, the on-chip heater, using the CRC checksum and reading
the serial number are not supported yet.
