| 1 | Kernel driver sht21 |
| 2 | =================== |
| 3 | |
| 4 | Supported chips: |
| 5 | |
| 6 | * Sensirion SHT21 |
| 7 | |
| 8 | Prefix: 'sht21' |
| 9 | |
| 10 | Addresses scanned: none |
| 11 | |
| 12 | Datasheet: Publicly available at the Sensirion website |
| 13 | |
| 14 | https://www.sensirion.com/file/datasheet_sht21 |
| 15 | |
| 16 | |
| 17 | |
| 18 | * Sensirion SHT25 |
| 19 | |
| 20 | Prefix: 'sht25' |
| 21 | |
| 22 | Addresses scanned: none |
| 23 | |
| 24 | Datasheet: Publicly available at the Sensirion website |
| 25 | |
| 26 | https://www.sensirion.com/file/datasheet_sht25 |
| 27 | |
| 28 | |
| 29 | |
| 30 | Author: |
| 31 | |
| 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 | |
| 50 | temp1_input |
| 51 | - temperature input |
| 52 | |
| 53 | humidity1_input |
| 54 | - humidity input |
| 55 | eic |
| 56 | - Electronic Identification Code |
| 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 | |
| 67 | Different resolutions, the on-chip heater, and using the CRC checksum |
| 68 | are not supported yet. |