17ebd8b66SMauro Carvalho ChehabKernel driver sht21 27ebd8b66SMauro Carvalho Chehab=================== 37ebd8b66SMauro Carvalho Chehab 47ebd8b66SMauro Carvalho ChehabSupported chips: 57ebd8b66SMauro Carvalho Chehab 67ebd8b66SMauro Carvalho Chehab * Sensirion SHT21 77ebd8b66SMauro Carvalho Chehab 87ebd8b66SMauro Carvalho Chehab Prefix: 'sht21' 97ebd8b66SMauro Carvalho Chehab 107ebd8b66SMauro Carvalho Chehab Addresses scanned: none 117ebd8b66SMauro Carvalho Chehab 127ebd8b66SMauro Carvalho Chehab Datasheet: Publicly available at the Sensirion website 137ebd8b66SMauro Carvalho Chehab 14ad736c1aSAlexander A. Klimov https://www.sensirion.com/file/datasheet_sht21 157ebd8b66SMauro Carvalho Chehab 167ebd8b66SMauro Carvalho Chehab 177ebd8b66SMauro Carvalho Chehab 187ebd8b66SMauro Carvalho Chehab * Sensirion SHT25 197ebd8b66SMauro Carvalho Chehab 207ebd8b66SMauro Carvalho Chehab Prefix: 'sht25' 217ebd8b66SMauro Carvalho Chehab 227ebd8b66SMauro Carvalho Chehab Addresses scanned: none 237ebd8b66SMauro Carvalho Chehab 247ebd8b66SMauro Carvalho Chehab Datasheet: Publicly available at the Sensirion website 257ebd8b66SMauro Carvalho Chehab 26ad736c1aSAlexander A. Klimov https://www.sensirion.com/file/datasheet_sht25 277ebd8b66SMauro Carvalho Chehab 287ebd8b66SMauro Carvalho Chehab 297ebd8b66SMauro Carvalho Chehab 307ebd8b66SMauro Carvalho ChehabAuthor: 317ebd8b66SMauro Carvalho Chehab 327ebd8b66SMauro Carvalho Chehab Urs Fleisch <urs.fleisch@sensirion.com> 337ebd8b66SMauro Carvalho Chehab 347ebd8b66SMauro Carvalho ChehabDescription 357ebd8b66SMauro Carvalho Chehab----------- 367ebd8b66SMauro Carvalho Chehab 377ebd8b66SMauro Carvalho ChehabThe SHT21 and SHT25 are humidity and temperature sensors in a DFN package of 387ebd8b66SMauro Carvalho Chehabonly 3 x 3 mm footprint and 1.1 mm height. The difference between the two 397ebd8b66SMauro Carvalho Chehabdevices is the higher level of precision of the SHT25 (1.8% relative humidity, 407ebd8b66SMauro Carvalho Chehab0.2 degree Celsius) compared with the SHT21 (2.0% relative humidity, 417ebd8b66SMauro Carvalho Chehab0.3 degree Celsius). 427ebd8b66SMauro Carvalho Chehab 437ebd8b66SMauro Carvalho ChehabThe devices communicate with the I2C protocol. All sensors are set to the same 447ebd8b66SMauro Carvalho ChehabI2C address 0x40, so an entry with I2C_BOARD_INFO("sht21", 0x40) can be used 457ebd8b66SMauro Carvalho Chehabin the board setup code. 467ebd8b66SMauro Carvalho Chehab 477ebd8b66SMauro Carvalho Chehabsysfs-Interface 487ebd8b66SMauro Carvalho Chehab--------------- 497ebd8b66SMauro Carvalho Chehab 507ebd8b66SMauro Carvalho Chehabtemp1_input 517ebd8b66SMauro Carvalho Chehab - temperature input 527ebd8b66SMauro Carvalho Chehab 537ebd8b66SMauro Carvalho Chehabhumidity1_input 547ebd8b66SMauro Carvalho Chehab - humidity input 557ebd8b66SMauro Carvalho Chehabeic 567ebd8b66SMauro Carvalho Chehab - Electronic Identification Code 577ebd8b66SMauro Carvalho Chehab 587ebd8b66SMauro Carvalho ChehabNotes 597ebd8b66SMauro Carvalho Chehab----- 607ebd8b66SMauro Carvalho Chehab 617ebd8b66SMauro Carvalho ChehabThe driver uses the default resolution settings of 12 bit for humidity and 14 627ebd8b66SMauro Carvalho Chehabbit for temperature, which results in typical measurement times of 22 ms for 637ebd8b66SMauro Carvalho Chehabhumidity and 66 ms for temperature. To keep self heating below 0.1 degree 647ebd8b66SMauro Carvalho ChehabCelsius, the device should not be active for more than 10% of the time, 657ebd8b66SMauro Carvalho Chehabe.g. maximum two measurements per second at the given resolution. 667ebd8b66SMauro Carvalho Chehab 677ebd8b66SMauro Carvalho ChehabDifferent resolutions, the on-chip heater, and using the CRC checksum 687ebd8b66SMauro Carvalho Chehabare not supported yet. 69