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Urs Fleisch430400b2011-01-07 07:15:39 +00001Kernel driver sht21
2===================
3
4Supported chips:
5 * Sensirion SHT21
6 Prefix: 'sht21'
7 Addresses scanned: none
8 Datasheet: Publicly available at the Sensirion website
9 http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT21.pdf
10
11 * Sensirion SHT25
12 Prefix: 'sht21'
13 Addresses scanned: none
14 Datasheet: Publicly available at the Sensirion website
15 http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT25.pdf
16
17Author:
18 Urs Fleisch <urs.fleisch@sensirion.com>
19
20Description
21-----------
22
23The SHT21 and SHT25 are humidity and temperature sensors in a DFN package of
24only 3 x 3 mm footprint and 1.1 mm height. The difference between the two
25devices is the higher level of precision of the SHT25 (1.8% relative humidity,
260.2 degree Celsius) compared with the SHT21 (2.0% relative humidity,
270.3 degree Celsius).
28
29The devices communicate with the I2C protocol. All sensors are set to the same
30I2C address 0x40, so an entry with I2C_BOARD_INFO("sht21", 0x40) can be used
31in the board setup code.
32
33sysfs-Interface
34---------------
35
36temp1_input - temperature input
37humidity1_input - humidity input
38
39Notes
40-----
41
42The driver uses the default resolution settings of 12 bit for humidity and 14
43bit for temperature, which results in typical measurement times of 22 ms for
44humidity and 66 ms for temperature. To keep self heating below 0.1 degree
45Celsius, the device should not be active for more than 10% of the time,
46e.g. maximum two measurements per second at the given resolution.
47
48Different resolutions, the on-chip heater, using the CRC checksum and reading
49the serial number are not supported yet.