1*4882a593SmuzhiyunKernel driver sht21 2*4882a593Smuzhiyun=================== 3*4882a593Smuzhiyun 4*4882a593SmuzhiyunSupported chips: 5*4882a593Smuzhiyun 6*4882a593Smuzhiyun * Sensirion SHT21 7*4882a593Smuzhiyun 8*4882a593Smuzhiyun Prefix: 'sht21' 9*4882a593Smuzhiyun 10*4882a593Smuzhiyun Addresses scanned: none 11*4882a593Smuzhiyun 12*4882a593Smuzhiyun Datasheet: Publicly available at the Sensirion website 13*4882a593Smuzhiyun 14*4882a593Smuzhiyun https://www.sensirion.com/file/datasheet_sht21 15*4882a593Smuzhiyun 16*4882a593Smuzhiyun 17*4882a593Smuzhiyun 18*4882a593Smuzhiyun * Sensirion SHT25 19*4882a593Smuzhiyun 20*4882a593Smuzhiyun Prefix: 'sht25' 21*4882a593Smuzhiyun 22*4882a593Smuzhiyun Addresses scanned: none 23*4882a593Smuzhiyun 24*4882a593Smuzhiyun Datasheet: Publicly available at the Sensirion website 25*4882a593Smuzhiyun 26*4882a593Smuzhiyun https://www.sensirion.com/file/datasheet_sht25 27*4882a593Smuzhiyun 28*4882a593Smuzhiyun 29*4882a593Smuzhiyun 30*4882a593SmuzhiyunAuthor: 31*4882a593Smuzhiyun 32*4882a593Smuzhiyun Urs Fleisch <urs.fleisch@sensirion.com> 33*4882a593Smuzhiyun 34*4882a593SmuzhiyunDescription 35*4882a593Smuzhiyun----------- 36*4882a593Smuzhiyun 37*4882a593SmuzhiyunThe SHT21 and SHT25 are humidity and temperature sensors in a DFN package of 38*4882a593Smuzhiyunonly 3 x 3 mm footprint and 1.1 mm height. The difference between the two 39*4882a593Smuzhiyundevices is the higher level of precision of the SHT25 (1.8% relative humidity, 40*4882a593Smuzhiyun0.2 degree Celsius) compared with the SHT21 (2.0% relative humidity, 41*4882a593Smuzhiyun0.3 degree Celsius). 42*4882a593Smuzhiyun 43*4882a593SmuzhiyunThe devices communicate with the I2C protocol. All sensors are set to the same 44*4882a593SmuzhiyunI2C address 0x40, so an entry with I2C_BOARD_INFO("sht21", 0x40) can be used 45*4882a593Smuzhiyunin the board setup code. 46*4882a593Smuzhiyun 47*4882a593Smuzhiyunsysfs-Interface 48*4882a593Smuzhiyun--------------- 49*4882a593Smuzhiyun 50*4882a593Smuzhiyuntemp1_input 51*4882a593Smuzhiyun - temperature input 52*4882a593Smuzhiyun 53*4882a593Smuzhiyunhumidity1_input 54*4882a593Smuzhiyun - humidity input 55*4882a593Smuzhiyuneic 56*4882a593Smuzhiyun - Electronic Identification Code 57*4882a593Smuzhiyun 58*4882a593SmuzhiyunNotes 59*4882a593Smuzhiyun----- 60*4882a593Smuzhiyun 61*4882a593SmuzhiyunThe driver uses the default resolution settings of 12 bit for humidity and 14 62*4882a593Smuzhiyunbit for temperature, which results in typical measurement times of 22 ms for 63*4882a593Smuzhiyunhumidity and 66 ms for temperature. To keep self heating below 0.1 degree 64*4882a593SmuzhiyunCelsius, the device should not be active for more than 10% of the time, 65*4882a593Smuzhiyune.g. maximum two measurements per second at the given resolution. 66*4882a593Smuzhiyun 67*4882a593SmuzhiyunDifferent resolutions, the on-chip heater, and using the CRC checksum 68*4882a593Smuzhiyunare not supported yet. 69