| Vivien Didelot | 99a0378 | 2011-04-12 15:34:36 -0400 | [diff] [blame] | 1 | Kernel driver sht15 |
| 2 | =================== |
| 3 | |
| 4 | Authors: |
| 5 | * Wouter Horre |
| 6 | * Jonathan Cameron |
| Vivien Didelot | cc15c7e | 2011-04-12 15:34:38 -0400 | [diff] [blame] | 7 | * Vivien Didelot <vivien.didelot@savoirfairelinux.com> |
| Jerome Oufella | 82c7465 | 2011-04-12 15:34:39 -0400 | [diff] [blame] | 8 | * Jerome Oufella <jerome.oufella@savoirfairelinux.com> |
| Vivien Didelot | 99a0378 | 2011-04-12 15:34:36 -0400 | [diff] [blame] | 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 | |
| Vivien Didelot | cc15c7e | 2011-04-12 15:34:38 -0400 | [diff] [blame] | 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. |
| Vivien Didelot | 99a0378 | 2011-04-12 15:34:36 -0400 | [diff] [blame] | 47 | |
| Jerome Oufella | 82c7465 | 2011-04-12 15:34:39 -0400 | [diff] [blame] | 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. |
| Vivien Didelot | 99a0378 | 2011-04-12 15:34:36 -0400 | [diff] [blame] | 53 | |
| Vivien Didelot | cc15c7e | 2011-04-12 15:34:38 -0400 | [diff] [blame] | 54 | Platform data |
| 55 | ------------- |
| 56 | |
| Jerome Oufella | 82c7465 | 2011-04-12 15:34:39 -0400 | [diff] [blame] | 57 | * checksum: |
| 58 | set it to true to enable CRC validation of the readings (default to false). |
| Vivien Didelot | cc15c7e | 2011-04-12 15:34:38 -0400 | [diff] [blame] | 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 | |
| Vivien Didelot | 99a0378 | 2011-04-12 15:34:36 -0400 | [diff] [blame] | 64 | Sysfs interface |
| 65 | --------------- |
| 66 | |
| 67 | * temp1_input: temperature input |
| 68 | * humidity1_input: humidity input |
| Vivien Didelot | cc15c7e | 2011-04-12 15:34:38 -0400 | [diff] [blame] | 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. |