| 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 |
| eic - Electronic Identification Code |
| |
| 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, and using the CRC checksum |
| are not supported yet. |