projects / linux-2.6-block.git / blame
| Commit | Line | Data |
|---|---|---|
| 99a0378d VD |
1 | Kernel driver sht15 |
| 2 | =================== | |
| 3 | ||
| 4 | Authors: | |
| 5 | * Wouter Horre | |
| 6 | * Jonathan Cameron | |
| cc15c7eb | 7 | * Vivien Didelot <vivien.didelot@savoirfairelinux.com> |
| 82c7465b | 8 | * Jerome Oufella <jerome.oufella@savoirfairelinux.com> |
| 99a0378d VD |
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 | ||
| cc15c7eb VD |
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 | |
| 1754e4c5 | 43 | measurement and decrease power consumption, while losing on precision. |
| cc15c7eb VD |
44 | |
| 45 | Some options may be set directly in the sht15_platform_data structure | |
| 46 | or via sysfs attributes. | |
| 99a0378d | 47 | |
| 82c7465b JO |
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. | |
| 99a0378d | 53 | |
| cc15c7eb VD |
54 | Platform data |
| 55 | ------------- | |
| 56 | ||
| 82c7465b JO |
57 | * checksum: |
| 58 | set it to true to enable CRC validation of the readings (default to false). | |
| cc15c7eb VD |
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 | ||
| 99a0378d VD |
64 | Sysfs interface |
| 65 | --------------- | |
| 66 | ||
| 67 | * temp1_input: temperature input | |
| 68 | * humidity1_input: humidity input | |
| cc15c7eb VD |
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. |