51 lines
1.6 KiB
Plaintext
Executable file
51 lines
1.6 KiB
Plaintext
Executable file
Kernel driver sht21
|
|
===================
|
|
|
|
Supported chips:
|
|
* Sensirion SHT21
|
|
Prefix: 'sht21'
|
|
Addresses scanned: none
|
|
Datasheet: Publicly available at the Sensirion website
|
|
http://www.sensirion.com/file/datasheet_sht21
|
|
|
|
* Sensirion SHT25
|
|
Prefix: 'sht25'
|
|
Addresses scanned: none
|
|
Datasheet: Publicly available at the Sensirion website
|
|
http://www.sensirion.com/file/datasheet_sht25
|
|
|
|
Author:
|
|
Urs Fleisch <urs.fleisch@sensirion.com>
|
|
|
|
Description
|
|
-----------
|
|
|
|
The SHT21 and SHT25 are humidity and temperature sensors in a DFN package of
|
|
only 3 x 3 mm footprint and 1.1 mm height. The difference between the two
|
|
devices is the higher level of precision of the SHT25 (1.8% relative humidity,
|
|
0.2 degree Celsius) compared with the SHT21 (2.0% relative humidity,
|
|
0.3 degree Celsius).
|
|
|
|
The devices communicate with the I2C protocol. All sensors are set to the same
|
|
I2C address 0x40, so an entry with I2C_BOARD_INFO("sht21", 0x40) can be used
|
|
in the board setup code.
|
|
|
|
sysfs-Interface
|
|
---------------
|
|
|
|
temp1_input - temperature input
|
|
humidity1_input - humidity input
|
|
eic - Electronic Identification Code
|
|
|
|
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 22 ms for
|
|
humidity and 66 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,
|
|
e.g. maximum two measurements per second at the given resolution.
|
|
|
|
Different resolutions, the on-chip heater, and using the CRC checksum
|
|
are not supported yet.
|