projects / linux-block.git / blame
| Commit | Line | Data |
|---|---|---|
| 430400b8 UF |
1 | Kernel driver sht21 |
| 2 | =================== | |
| 3 | ||
| 4 | Supported chips: | |
| b04f2f7d | 5 | |
| 430400b8 | 6 | * Sensirion SHT21 |
| b04f2f7d | 7 | |
| 430400b8 | 8 | Prefix: 'sht21' |
| b04f2f7d | 9 | |
| 430400b8 | 10 | Addresses scanned: none |
| b04f2f7d | 11 | |
| 430400b8 | 12 | Datasheet: Publicly available at the Sensirion website |
| b04f2f7d | 13 | |
| ad736c1a | 14 | https://www.sensirion.com/file/datasheet_sht21 |
| 430400b8 | 15 | |
| b04f2f7d MCC |
16 | |
| 17 | ||
| 430400b8 | 18 | * Sensirion SHT25 |
| b04f2f7d | 19 | |
| 8e1d6fe9 | 20 | Prefix: 'sht25' |
| b04f2f7d | 21 | |
| 430400b8 | 22 | Addresses scanned: none |
| b04f2f7d | 23 | |
| 430400b8 | 24 | Datasheet: Publicly available at the Sensirion website |
| b04f2f7d | 25 | |
| ad736c1a | 26 | https://www.sensirion.com/file/datasheet_sht25 |
| 430400b8 | 27 | |
| b04f2f7d MCC |
28 | |
| 29 | ||
| 430400b8 | 30 | Author: |
| b04f2f7d | 31 | |
| 430400b8 UF |
32 | Urs Fleisch <urs.fleisch@sensirion.com> |
| 33 | ||
| 34 | Description | |
| 35 | ----------- | |
| 36 | ||
| 37 | The SHT21 and SHT25 are humidity and temperature sensors in a DFN package of | |
| 38 | only 3 x 3 mm footprint and 1.1 mm height. The difference between the two | |
| 39 | devices is the higher level of precision of the SHT25 (1.8% relative humidity, | |
| 40 | 0.2 degree Celsius) compared with the SHT21 (2.0% relative humidity, | |
| 41 | 0.3 degree Celsius). | |
| 42 | ||
| 43 | The devices communicate with the I2C protocol. All sensors are set to the same | |
| 44 | I2C address 0x40, so an entry with I2C_BOARD_INFO("sht21", 0x40) can be used | |
| 45 | in the board setup code. | |
| 46 | ||
| 47 | sysfs-Interface | |
| 48 | --------------- | |
| 49 | ||
| b04f2f7d MCC |
50 | temp1_input |
| 51 | - temperature input | |
| 52 | ||
| 53 | humidity1_input | |
| 54 | - humidity input | |
| 55 | eic | |
| 56 | - Electronic Identification Code | |
| 430400b8 UF |
57 | |
| 58 | Notes | |
| 59 | ----- | |
| 60 | ||
| 61 | The driver uses the default resolution settings of 12 bit for humidity and 14 | |
| 62 | bit for temperature, which results in typical measurement times of 22 ms for | |
| 63 | humidity and 66 ms for temperature. To keep self heating below 0.1 degree | |
| 64 | Celsius, the device should not be active for more than 10% of the time, | |
| 65 | e.g. maximum two measurements per second at the given resolution. | |
| 66 | ||
| 53e678d7 PB |
67 | Different resolutions, the on-chip heater, and using the CRC checksum |
| 68 | are not supported yet. |