sht3x.rst

  1Kernel driver sht3x
  2===================
  3
  4Supported chips:
  5
  6  * Sensirion SHT3x-DIS
  7
  8    Prefix: 'sht3x'
  9
 10    Addresses scanned: none
 11
 12    Datasheets:
 13        - https://sensirion.com/media/documents/213E6A3B/63A5A569/Datasheet_SHT3x_DIS.pdf
 14        - https://sensirion.com/media/documents/051DF50B/639C8101/Sensirion_Humidity_and_Temperature_Sensors_Datasheet_SHT33.pdf
 15
 16  * Sensirion STS3x-DIS
 17
 18    Prefix: 'sts3x'
 19
 20    Addresses scanned: none
 21
 22    Datasheets:
 23        - https://sensirion.com/media/documents/1DA31AFD/61641F76/Sensirion_Temperature_Sensors_STS3x_Datasheet.pdf
 24        - https://sensirion.com/media/documents/292A335C/65537BAF/Sensirion_Datasheet_STS32_STS33.pdf
 25
 26Author:
 27
 28  - David Frey <david.frey@sensirion.com>
 29  - Pascal Sachs <pascal.sachs@sensirion.com>
 30
 31Description
 32-----------
 33
 34This driver implements support for the Sensirion SHT3x-DIS and STS3x-DIS
 35series of humidity and temperature sensors. Temperature is measured in degrees
 36celsius, relative humidity is expressed as a percentage. In the sysfs interface,
 37all values are scaled by 1000, i.e. the value for 31.5 degrees celsius is 31500.
 38
 39The device communicates with the I2C protocol. Sensors can have the I2C
 40addresses 0x44 or 0x45 (0x4a or 0x4b for sts3x), depending on the wiring. See
 41Documentation/i2c/instantiating-devices.rst for methods to instantiate the
 42device.
 43
 44Even if sht3x sensor supports clock-stretch (blocking mode) and non-stretch
 45(non-blocking mode) in single-shot mode, this driver only supports the latter.
 46
 47The sht3x sensor supports a single shot mode as well as 5 periodic measure
 48modes, which can be controlled with the update_interval sysfs interface.
 49The allowed update_interval in milliseconds are as follows:
 50
 51    ===== ======= ====================
 52       0          single shot mode
 53    2000   0.5 Hz periodic measurement
 54    1000   1   Hz periodic measurement
 55     500   2   Hz periodic measurement
 56     250   4   Hz periodic measurement
 57     100  10   Hz periodic measurement
 58    ===== ======= ====================
 59
 60In the periodic measure mode, the sensor automatically triggers a measurement
 61with the configured update interval on the chip. When a temperature or humidity
 62reading exceeds the configured limits, the alert attribute is set to 1 and
 63the alert pin on the sensor is set to high.
 64When the temperature and humidity readings move back between the hysteresis
 65values, the alert bit is set to 0 and the alert pin on the sensor is set to
 66low.
 67
 68The serial number exposed to debugfs allows for unique identification of the
 69sensors. For sts32, sts33 and sht33, the manufacturer provides calibration
 70certificates through an API.
 71
 72sysfs-Interface
 73---------------
 74
 75=================== ============================================================
 76temp1_input:        temperature input
 77humidity1_input:    humidity input
 78temp1_max:          temperature max value
 79temp1_max_hyst:     temperature hysteresis value for max limit
 80humidity1_max:      humidity max value
 81humidity1_max_hyst: humidity hysteresis value for max limit
 82temp1_min:          temperature min value
 83temp1_min_hyst:     temperature hysteresis value for min limit
 84humidity1_min:      humidity min value
 85humidity1_min_hyst: humidity hysteresis value for min limit
 86temp1_alarm:        alarm flag is set to 1 if the temperature is outside the
 87		    configured limits. Alarm only works in periodic measure mode
 88humidity1_alarm:    alarm flag is set to 1 if the humidity is outside the
 89		    configured limits. Alarm only works in periodic measure mode
 90heater_enable:      heater enable, heating element removes excess humidity from
 91		    sensor:
 92
 93			- 0: turned off
 94			- 1: turned on
 95update_interval:    update interval, 0 for single shot, interval in msec
 96		    for periodic measurement. If the interval is not supported
 97		    by the sensor, the next faster interval is chosen
 98repeatability:      write or read repeatability, higher repeatability means
 99                    longer measurement duration, lower noise level and
100                    larger energy consumption:
101
102                        - 0: low repeatability
103                        - 1: medium repeatability
104                        - 2: high repeatability
105=================== ============================================================
106
107debugfs-Interface
108-----------------
109
110=================== ============================================================
111serial_number:      unique serial number of the sensor in decimal
112=================== ============================================================