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7c84f7f8 DF |
1 | Kernel driver sht3x |
2 | =================== | |
3 | ||
4 | Supported chips: | |
5 | * Sensirion SHT3x-DIS | |
6 | Prefix: 'sht3x' | |
7 | Addresses scanned: none | |
8 | Datasheet: http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_Datasheet_SHT3x_DIS.pdf | |
9 | ||
10 | Author: | |
11 | David Frey <david.frey@sensirion.com> | |
12 | Pascal Sachs <pascal.sachs@sensirion.com> | |
13 | ||
14 | Description | |
15 | ----------- | |
16 | ||
17 | This driver implements support for the Sensirion SHT3x-DIS chip, a humidity | |
18 | and temperature sensor. Temperature is measured in degrees celsius, relative | |
19 | humidity is expressed as a percentage. In the sysfs interface, all values are | |
20 | scaled by 1000, i.e. the value for 31.5 degrees celsius is 31500. | |
21 | ||
22 | The device communicates with the I2C protocol. Sensors can have the I2C | |
23 | addresses 0x44 or 0x45, depending on the wiring. See | |
24 | Documentation/i2c/instantiating-devices for methods to instantiate the device. | |
25 | ||
26 | There are two options configurable by means of sht3x_platform_data: | |
27 | 1. blocking (pull the I2C clock line down while performing the measurement) or | |
28 | non-blocking mode. Blocking mode will guarantee the fastest result but | |
29 | the I2C bus will be busy during that time. By default, non-blocking mode | |
30 | is used. Make sure clock-stretching works properly on your device if you | |
31 | want to use blocking mode. | |
32 | 2. high or low accuracy. High accuracy is used by default and using it is | |
33 | strongly recommended. | |
34 | ||
35 | The sht3x sensor supports a single shot mode as well as 5 periodic measure | |
36 | modes, which can be controlled with the update_interval sysfs interface. | |
37 | The allowed update_interval in milliseconds are as follows: | |
38 | * 0 single shot mode | |
39 | * 2000 0.5 Hz periodic measurement | |
40 | * 1000 1 Hz periodic measurement | |
41 | * 500 2 Hz periodic measurement | |
42 | * 250 4 Hz periodic measurement | |
43 | * 100 10 Hz periodic measurement | |
44 | ||
45 | In the periodic measure mode, the sensor automatically triggers a measurement | |
46 | with the configured update interval on the chip. When a temperature or humidity | |
47 | reading exceeds the configured limits, the alert attribute is set to 1 and | |
48 | the alert pin on the sensor is set to high. | |
49 | When the temperature and humidity readings move back between the hysteresis | |
50 | values, the alert bit is set to 0 and the alert pin on the sensor is set to | |
51 | low. | |
52 | ||
53 | sysfs-Interface | |
54 | --------------- | |
55 | ||
56 | temp1_input: temperature input | |
57 | humidity1_input: humidity input | |
58 | temp1_max: temperature max value | |
59 | temp1_max_hyst: temperature hysteresis value for max limit | |
60 | humidity1_max: humidity max value | |
61 | humidity1_max_hyst: humidity hysteresis value for max limit | |
62 | temp1_min: temperature min value | |
63 | temp1_min_hyst: temperature hysteresis value for min limit | |
64 | humidity1_min: humidity min value | |
65 | humidity1_min_hyst: humidity hysteresis value for min limit | |
66 | temp1_alarm: alarm flag is set to 1 if the temperature is outside the | |
67 | configured limits. Alarm only works in periodic measure mode | |
68 | humidity1_alarm: alarm flag is set to 1 if the humidity is outside the | |
69 | configured limits. Alarm only works in periodic measure mode | |
50c22cd1 MR |
70 | heater_enable: heater enable, heating element removes excess humidity from |
71 | sensor | |
72 | 0: turned off | |
73 | 1: turned on | |
7c84f7f8 DF |
74 | update_interval: update interval, 0 for single shot, interval in msec |
75 | for periodic measurement. If the interval is not supported | |
76 | by the sensor, the next faster interval is chosen |