1Kernel driver sht3x
2===================
3
4Supported chips:
5
6  * Sensirion SHT3x-DIS
7
8    Prefix: 'sht3x'
9
10    Addresses scanned: none
11
12    Datasheet: https://www.sensirion.com/file/datasheet_sht3x_digital
13
14Author:
15
16  - David Frey <david.frey@sensirion.com>
17  - Pascal Sachs <pascal.sachs@sensirion.com>
18
19Description
20-----------
21
22This driver implements support for the Sensirion SHT3x-DIS chip, a humidity
23and temperature sensor. Temperature is measured in degrees celsius, relative
24humidity is expressed as a percentage. In the sysfs interface, all values are
25scaled by 1000, i.e. the value for 31.5 degrees celsius is 31500.
26
27The device communicates with the I2C protocol. Sensors can have the I2C
28addresses 0x44 or 0x45, depending on the wiring. See
29Documentation/i2c/instantiating-devices.rst for methods to instantiate the device.
30
31Even if sht3x sensor supports clock-strech(blocking mode) and non-strench
32(non-blocking mode) in single-shot mode, this driver only supports the latter.
33
34The sht3x sensor supports a single shot mode as well as 5 periodic measure
35modes, which can be controlled with the update_interval sysfs interface.
36The allowed update_interval in milliseconds are as follows:
37
38    ===== ======= ====================
39       0          single shot mode
40    2000   0.5 Hz periodic measurement
41    1000   1   Hz periodic measurement
42     500   2   Hz periodic measurement
43     250   4   Hz periodic measurement
44     100  10   Hz periodic measurement
45    ===== ======= ====================
46
47In the periodic measure mode, the sensor automatically triggers a measurement
48with the configured update interval on the chip. When a temperature or humidity
49reading exceeds the configured limits, the alert attribute is set to 1 and
50the alert pin on the sensor is set to high.
51When the temperature and humidity readings move back between the hysteresis
52values, the alert bit is set to 0 and the alert pin on the sensor is set to
53low.
54
55sysfs-Interface
56---------------
57
58=================== ============================================================
59temp1_input:        temperature input
60humidity1_input:    humidity input
61temp1_max:          temperature max value
62temp1_max_hyst:     temperature hysteresis value for max limit
63humidity1_max:      humidity max value
64humidity1_max_hyst: humidity hysteresis value for max limit
65temp1_min:          temperature min value
66temp1_min_hyst:     temperature hysteresis value for min limit
67humidity1_min:      humidity min value
68humidity1_min_hyst: humidity hysteresis value for min limit
69temp1_alarm:        alarm flag is set to 1 if the temperature is outside the
70		    configured limits. Alarm only works in periodic measure mode
71humidity1_alarm:    alarm flag is set to 1 if the humidity is outside the
72		    configured limits. Alarm only works in periodic measure mode
73heater_enable:      heater enable, heating element removes excess humidity from
74		    sensor:
75
76			- 0: turned off
77			- 1: turned on
78update_interval:    update interval, 0 for single shot, interval in msec
79		    for periodic measurement. If the interval is not supported
80		    by the sensor, the next faster interval is chosen
81repeatability:      write or read repeatability, higher repeatability means
82                    longer measurement duration, lower noise level and
83                    larger energy consumption:
84
85                        - 0: low repeatability
86                        - 1: medium repeatability
87                        - 2: high repeatability
88=================== ============================================================
89