1Kernel driver sht21 2=================== 3 4Supported 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 http://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 http://www.sensirion.com/file/datasheet_sht25 27 28 29 30Author: 31 32 Urs Fleisch <urs.fleisch@sensirion.com> 33 34Description 35----------- 36 37The SHT21 and SHT25 are humidity and temperature sensors in a DFN package of 38only 3 x 3 mm footprint and 1.1 mm height. The difference between the two 39devices is the higher level of precision of the SHT25 (1.8% relative humidity, 400.2 degree Celsius) compared with the SHT21 (2.0% relative humidity, 410.3 degree Celsius). 42 43The devices communicate with the I2C protocol. All sensors are set to the same 44I2C address 0x40, so an entry with I2C_BOARD_INFO("sht21", 0x40) can be used 45in the board setup code. 46 47sysfs-Interface 48--------------- 49 50temp1_input 51 - temperature input 52 53humidity1_input 54 - humidity input 55eic 56 - Electronic Identification Code 57 58Notes 59----- 60 61The driver uses the default resolution settings of 12 bit for humidity and 14 62bit for temperature, which results in typical measurement times of 22 ms for 63humidity and 66 ms for temperature. To keep self heating below 0.1 degree 64Celsius, the device should not be active for more than 10% of the time, 65e.g. maximum two measurements per second at the given resolution. 66 67Different resolutions, the on-chip heater, and using the CRC checksum 68are not supported yet. 69