1 Kernel driver sht21
2 ===================
3
4 Supported chips:
5
6 * Sensirion SHT21
7
8 Prefix: 'sht21'
9
10 Addresses scanned: none
11
12 Datasheet: Publicly available at the Sensirion website
13
14 https://www.sensirion.com/file/datasheet_sht21
15
16
17
18 * Sensirion SHT25
19
20 Prefix: 'sht25'
21
22 Addresses scanned: none
23
24 Datasheet: Publicly available at the Sensirion website
25
26 https://www.sensirion.com/file/datasheet_sht25
27
28
29
30 Author:
31
32 Urs Fleisch <urs.fleisch@sensirion.com>
33
34 Description
35 -----------
36
37 The SHT21 and SHT25 are humidity and temperature sensors in a DFN package of
38 only 3 x 3 mm footprint and 1.1 mm height. The difference between the two
39 devices is the higher level of precision of the SHT25 (1.8% relative humidity,
40 0.2 degree Celsius) compared with the SHT21 (2.0% relative humidity,
41 0.3 degree Celsius).
42
43 The devices communicate with the I2C protocol. All sensors are set to the same
44 I2C address 0x40, so an entry with I2C_BOARD_INFO("sht21", 0x40) can be used
45 in the board setup code.
46
47 sysfs-Interface
48 ---------------
49
50 temp1_input
51 - temperature input
52
53 humidity1_input
54 - humidity input
55 eic
56 - Electronic Identification Code
57
58 Notes
59 -----
60
61 The driver uses the default resolution settings of 12 bit for humidity and 14
62 bit for temperature, which results in typical measurement times of 22 ms for
63 humidity and 66 ms for temperature. To keep self heating below 0.1 degree
64 Celsius, the device should not be active for more than 10% of the time,
65 e.g. maximum two measurements per second at the given resolution.
66
67 Different resolutions, the on-chip heater, and using the CRC checksum
68 are not supported yet.
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