1*7ebd8b66SMauro Carvalho ChehabKernel driver sht15 2*7ebd8b66SMauro Carvalho Chehab=================== 3*7ebd8b66SMauro Carvalho Chehab 4*7ebd8b66SMauro Carvalho ChehabAuthors: 5*7ebd8b66SMauro Carvalho Chehab 6*7ebd8b66SMauro Carvalho Chehab * Wouter Horre 7*7ebd8b66SMauro Carvalho Chehab * Jonathan Cameron 8*7ebd8b66SMauro Carvalho Chehab * Vivien Didelot <vivien.didelot@savoirfairelinux.com> 9*7ebd8b66SMauro Carvalho Chehab * Jerome Oufella <jerome.oufella@savoirfairelinux.com> 10*7ebd8b66SMauro Carvalho Chehab 11*7ebd8b66SMauro Carvalho ChehabSupported chips: 12*7ebd8b66SMauro Carvalho Chehab 13*7ebd8b66SMauro Carvalho Chehab * Sensirion SHT10 14*7ebd8b66SMauro Carvalho Chehab 15*7ebd8b66SMauro Carvalho Chehab Prefix: 'sht10' 16*7ebd8b66SMauro Carvalho Chehab 17*7ebd8b66SMauro Carvalho Chehab * Sensirion SHT11 18*7ebd8b66SMauro Carvalho Chehab 19*7ebd8b66SMauro Carvalho Chehab Prefix: 'sht11' 20*7ebd8b66SMauro Carvalho Chehab 21*7ebd8b66SMauro Carvalho Chehab * Sensirion SHT15 22*7ebd8b66SMauro Carvalho Chehab 23*7ebd8b66SMauro Carvalho Chehab Prefix: 'sht15' 24*7ebd8b66SMauro Carvalho Chehab 25*7ebd8b66SMauro Carvalho Chehab * Sensirion SHT71 26*7ebd8b66SMauro Carvalho Chehab 27*7ebd8b66SMauro Carvalho Chehab Prefix: 'sht71' 28*7ebd8b66SMauro Carvalho Chehab 29*7ebd8b66SMauro Carvalho Chehab * Sensirion SHT75 30*7ebd8b66SMauro Carvalho Chehab 31*7ebd8b66SMauro Carvalho Chehab Prefix: 'sht75' 32*7ebd8b66SMauro Carvalho Chehab 33*7ebd8b66SMauro Carvalho ChehabDatasheet: Publicly available at the Sensirion website 34*7ebd8b66SMauro Carvalho Chehab 35*7ebd8b66SMauro Carvalho Chehab http://www.sensirion.ch/en/pdf/product_information/Datasheet-humidity-sensor-SHT1x.pdf 36*7ebd8b66SMauro Carvalho Chehab 37*7ebd8b66SMauro Carvalho ChehabDescription 38*7ebd8b66SMauro Carvalho Chehab----------- 39*7ebd8b66SMauro Carvalho Chehab 40*7ebd8b66SMauro Carvalho ChehabThe SHT10, SHT11, SHT15, SHT71, and SHT75 are humidity and temperature 41*7ebd8b66SMauro Carvalho Chehabsensors. 42*7ebd8b66SMauro Carvalho Chehab 43*7ebd8b66SMauro Carvalho ChehabThe devices communicate using two GPIO lines. 44*7ebd8b66SMauro Carvalho Chehab 45*7ebd8b66SMauro Carvalho ChehabSupported resolutions for the measurements are 14 bits for temperature and 12 46*7ebd8b66SMauro Carvalho Chehabbits for humidity, or 12 bits for temperature and 8 bits for humidity. 47*7ebd8b66SMauro Carvalho Chehab 48*7ebd8b66SMauro Carvalho ChehabThe humidity calibration coefficients are programmed into an OTP memory on the 49*7ebd8b66SMauro Carvalho Chehabchip. These coefficients are used to internally calibrate the signals from the 50*7ebd8b66SMauro Carvalho Chehabsensors. Disabling the reload of those coefficients allows saving 10ms for each 51*7ebd8b66SMauro Carvalho Chehabmeasurement and decrease power consumption, while losing on precision. 52*7ebd8b66SMauro Carvalho Chehab 53*7ebd8b66SMauro Carvalho ChehabSome options may be set via sysfs attributes. 54*7ebd8b66SMauro Carvalho Chehab 55*7ebd8b66SMauro Carvalho ChehabNotes: 56*7ebd8b66SMauro Carvalho Chehab * The regulator supply name is set to "vcc". 57*7ebd8b66SMauro Carvalho Chehab * If a CRC validation fails, a soft reset command is sent, which resets 58*7ebd8b66SMauro Carvalho Chehab status register to its hardware default value, but the driver will try to 59*7ebd8b66SMauro Carvalho Chehab restore the previous device configuration. 60*7ebd8b66SMauro Carvalho Chehab 61*7ebd8b66SMauro Carvalho ChehabPlatform data 62*7ebd8b66SMauro Carvalho Chehab------------- 63*7ebd8b66SMauro Carvalho Chehab 64*7ebd8b66SMauro Carvalho Chehab* checksum: 65*7ebd8b66SMauro Carvalho Chehab set it to true to enable CRC validation of the readings (default to false). 66*7ebd8b66SMauro Carvalho Chehab* no_otp_reload: 67*7ebd8b66SMauro Carvalho Chehab flag to indicate not to reload from OTP (default to false). 68*7ebd8b66SMauro Carvalho Chehab* low_resolution: 69*7ebd8b66SMauro Carvalho Chehab flag to indicate the temp/humidity resolution to use (default to false). 70*7ebd8b66SMauro Carvalho Chehab 71*7ebd8b66SMauro Carvalho ChehabSysfs interface 72*7ebd8b66SMauro Carvalho Chehab--------------- 73*7ebd8b66SMauro Carvalho Chehab 74*7ebd8b66SMauro Carvalho Chehab================== ========================================================== 75*7ebd8b66SMauro Carvalho Chehabtemp1_input temperature input 76*7ebd8b66SMauro Carvalho Chehabhumidity1_input humidity input 77*7ebd8b66SMauro Carvalho Chehabheater_enable write 1 in this attribute to enable the on-chip heater, 78*7ebd8b66SMauro Carvalho Chehab 0 to disable it. Be careful not to enable the heater 79*7ebd8b66SMauro Carvalho Chehab for too long. 80*7ebd8b66SMauro Carvalho Chehabtemp1_fault if 1, this means that the voltage is low (below 2.47V) and 81*7ebd8b66SMauro Carvalho Chehab measurement may be invalid. 82*7ebd8b66SMauro Carvalho Chehabhumidity1_fault same as temp1_fault. 83*7ebd8b66SMauro Carvalho Chehab================== ========================================================== 84