| Kernel driver sht21 | |
| =================== | |
| Supported chips: | |
| * Sensirion SHT21 | |
| Prefix: 'sht21' | |
| Addresses scanned: none | |
| Datasheet: Publicly available at the Sensirion website | |
| http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT21.pdf | |
| * Sensirion SHT25 | |
| Prefix: 'sht21' | |
| Addresses scanned: none | |
| Datasheet: Publicly available at the Sensirion website | |
| http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT25.pdf | |
| Author: | |
| Urs Fleisch <urs.fleisch@sensirion.com> | |
| Description | |
| ----------- | |
| The SHT21 and SHT25 are humidity and temperature sensors in a DFN package of | |
| only 3 x 3 mm footprint and 1.1 mm height. The difference between the two | |
| devices is the higher level of precision of the SHT25 (1.8% relative humidity, | |
| 0.2 degree Celsius) compared with the SHT21 (2.0% relative humidity, | |
| 0.3 degree Celsius). | |
| The devices communicate with the I2C protocol. All sensors are set to the same | |
| I2C address 0x40, so an entry with I2C_BOARD_INFO("sht21", 0x40) can be used | |
| in the board setup code. | |
| sysfs-Interface | |
| --------------- | |
| temp1_input - temperature input | |
| humidity1_input - humidity input | |
| Notes | |
| ----- | |
| The driver uses the default resolution settings of 12 bit for humidity and 14 | |
| bit for temperature, which results in typical measurement times of 22 ms for | |
| humidity and 66 ms for temperature. To keep self heating below 0.1 degree | |
| Celsius, the device should not be active for more than 10% of the time, | |
| e.g. maximum two measurements per second at the given resolution. | |
| Different resolutions, the on-chip heater, using the CRC checksum and reading | |
| the serial number are not supported yet. |