1Kernel driver sht21 2=================== 3 4Supported chips: 5 * Sensirion SHT21 6 Prefix: 'sht21' 7 Addresses scanned: none 8 Datasheet: Publicly available at the Sensirion website 9 http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT21.pdf 10 11 * Sensirion SHT25 12 Prefix: 'sht21' 13 Addresses scanned: none 14 Datasheet: Publicly available at the Sensirion website 15 http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT25.pdf 16 17Author: 18 Urs Fleisch <urs.fleisch@sensirion.com> 19 20Description 21----------- 22 23The SHT21 and SHT25 are humidity and temperature sensors in a DFN package of 24only 3 x 3 mm footprint and 1.1 mm height. The difference between the two 25devices is the higher level of precision of the SHT25 (1.8% relative humidity, 260.2 degree Celsius) compared with the SHT21 (2.0% relative humidity, 270.3 degree Celsius). 28 29The devices communicate with the I2C protocol. All sensors are set to the same 30I2C address 0x40, so an entry with I2C_BOARD_INFO("sht21", 0x40) can be used 31in the board setup code. 32 33sysfs-Interface 34--------------- 35 36temp1_input - temperature input 37humidity1_input - humidity input 38 39Notes 40----- 41 42The driver uses the default resolution settings of 12 bit for humidity and 14 43bit for temperature, which results in typical measurement times of 22 ms for 44humidity and 66 ms for temperature. To keep self heating below 0.1 degree 45Celsius, the device should not be active for more than 10% of the time, 46e.g. maximum two measurements per second at the given resolution. 47 48Different resolutions, the on-chip heater, using the CRC checksum and reading 49the serial number are not supported yet. 50