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1 | Kernel driver sht15 | ||
2 | =================== | ||
3 | |||
4 | Authors: | ||
5 | * Wouter Horre | ||
6 | * Jonathan Cameron | ||
7 | * Vivien Didelot <vivien.didelot@savoirfairelinux.com> | ||
8 | * Jerome Oufella <jerome.oufella@savoirfairelinux.com> | ||
9 | |||
10 | Supported chips: | ||
11 | * Sensirion SHT10 | ||
12 | Prefix: 'sht10' | ||
13 | |||
14 | * Sensirion SHT11 | ||
15 | Prefix: 'sht11' | ||
16 | |||
17 | * Sensirion SHT15 | ||
18 | Prefix: 'sht15' | ||
19 | |||
20 | * Sensirion SHT71 | ||
21 | Prefix: 'sht71' | ||
22 | |||
23 | * Sensirion SHT75 | ||
24 | Prefix: 'sht75' | ||
25 | |||
26 | Datasheet: Publicly available at the Sensirion website | ||
27 | http://www.sensirion.ch/en/pdf/product_information/Datasheet-humidity-sensor-SHT1x.pdf | ||
28 | |||
29 | Description | ||
30 | ----------- | ||
31 | |||
32 | The SHT10, SHT11, SHT15, SHT71, and SHT75 are humidity and temperature | ||
33 | sensors. | ||
34 | |||
35 | The devices communicate using two GPIO lines. | ||
36 | |||
37 | Supported resolutions for the measurements are 14 bits for temperature and 12 | ||
38 | bits for humidity, or 12 bits for temperature and 8 bits for humidity. | ||
39 | |||
40 | The humidity calibration coefficients are programmed into an OTP memory on the | ||
41 | chip. These coefficients are used to internally calibrate the signals from the | ||
42 | sensors. Disabling the reload of those coefficients allows saving 10ms for each | ||
43 | measurement and decrease power consumption, while loosing on precision. | ||
44 | |||
45 | Some options may be set directly in the sht15_platform_data structure | ||
46 | or via sysfs attributes. | ||
47 | |||
48 | Notes: | ||
49 | * The regulator supply name is set to "vcc". | ||
50 | * If a CRC validation fails, a soft reset command is sent, which resets | ||
51 | status register to its hardware default value, but the driver will try to | ||
52 | restore the previous device configuration. | ||
53 | |||
54 | Platform data | ||
55 | ------------- | ||
56 | |||
57 | * checksum: | ||
58 | set it to true to enable CRC validation of the readings (default to false). | ||
59 | * no_otp_reload: | ||
60 | flag to indicate not to reload from OTP (default to false). | ||
61 | * low_resolution: | ||
62 | flag to indicate the temp/humidity resolution to use (default to false). | ||
63 | |||
64 | Sysfs interface | ||
65 | --------------- | ||
66 | |||
67 | * temp1_input: temperature input | ||
68 | * humidity1_input: humidity input | ||
69 | * heater_enable: write 1 in this attribute to enable the on-chip heater, | ||
70 | 0 to disable it. Be careful not to enable the heater | ||
71 | for too long. | ||
72 | * temp1_fault: if 1, this means that the voltage is low (below 2.47V) and | ||
73 | measurement may be invalid. | ||
74 | * humidity1_fault: same as temp1_fault. | ||