113 lines
4.4 KiB
ReStructuredText
113 lines
4.4 KiB
ReStructuredText
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Kernel driver sht3x
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===================
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Supported chips:
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* Sensirion SHT3x-DIS
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Prefix: 'sht3x'
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Addresses scanned: none
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Datasheets:
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- https://sensirion.com/media/documents/213E6A3B/63A5A569/Datasheet_SHT3x_DIS.pdf
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- https://sensirion.com/media/documents/051DF50B/639C8101/Sensirion_Humidity_and_Temperature_Sensors_Datasheet_SHT33.pdf
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* Sensirion STS3x-DIS
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Prefix: 'sts3x'
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Addresses scanned: none
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Datasheets:
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- https://sensirion.com/media/documents/1DA31AFD/61641F76/Sensirion_Temperature_Sensors_STS3x_Datasheet.pdf
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- https://sensirion.com/media/documents/292A335C/65537BAF/Sensirion_Datasheet_STS32_STS33.pdf
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Author:
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- David Frey <david.frey@sensirion.com>
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- Pascal Sachs <pascal.sachs@sensirion.com>
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Description
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-----------
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This driver implements support for the Sensirion SHT3x-DIS and STS3x-DIS
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series of humidity and temperature sensors. Temperature is measured in degrees
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celsius, relative humidity is expressed as a percentage. In the sysfs interface,
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all values are scaled by 1000, i.e. the value for 31.5 degrees celsius is 31500.
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The device communicates with the I2C protocol. Sensors can have the I2C
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addresses 0x44 or 0x45 (0x4a or 0x4b for sts3x), depending on the wiring. See
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Documentation/i2c/instantiating-devices.rst for methods to instantiate the
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device.
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Even if sht3x sensor supports clock-stretch (blocking mode) and non-stretch
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(non-blocking mode) in single-shot mode, this driver only supports the latter.
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The sht3x sensor supports a single shot mode as well as 5 periodic measure
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modes, which can be controlled with the update_interval sysfs interface.
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The allowed update_interval in milliseconds are as follows:
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===== ======= ====================
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0 single shot mode
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2000 0.5 Hz periodic measurement
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1000 1 Hz periodic measurement
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500 2 Hz periodic measurement
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250 4 Hz periodic measurement
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100 10 Hz periodic measurement
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===== ======= ====================
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In the periodic measure mode, the sensor automatically triggers a measurement
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with the configured update interval on the chip. When a temperature or humidity
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reading exceeds the configured limits, the alert attribute is set to 1 and
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the alert pin on the sensor is set to high.
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When the temperature and humidity readings move back between the hysteresis
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values, the alert bit is set to 0 and the alert pin on the sensor is set to
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low.
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The serial number exposed to debugfs allows for unique identification of the
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sensors. For sts32, sts33 and sht33, the manufacturer provides calibration
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certificates through an API.
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sysfs-Interface
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---------------
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=================== ============================================================
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temp1_input: temperature input
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humidity1_input: humidity input
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temp1_max: temperature max value
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temp1_max_hyst: temperature hysteresis value for max limit
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humidity1_max: humidity max value
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humidity1_max_hyst: humidity hysteresis value for max limit
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temp1_min: temperature min value
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temp1_min_hyst: temperature hysteresis value for min limit
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humidity1_min: humidity min value
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humidity1_min_hyst: humidity hysteresis value for min limit
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temp1_alarm: alarm flag is set to 1 if the temperature is outside the
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configured limits. Alarm only works in periodic measure mode
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humidity1_alarm: alarm flag is set to 1 if the humidity is outside the
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configured limits. Alarm only works in periodic measure mode
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heater_enable: heater enable, heating element removes excess humidity from
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sensor:
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- 0: turned off
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- 1: turned on
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update_interval: update interval, 0 for single shot, interval in msec
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for periodic measurement. If the interval is not supported
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by the sensor, the next faster interval is chosen
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repeatability: write or read repeatability, higher repeatability means
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longer measurement duration, lower noise level and
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larger energy consumption:
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- 0: low repeatability
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- 1: medium repeatability
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- 2: high repeatability
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=================== ============================================================
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debugfs-Interface
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-----------------
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=================== ============================================================
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serial_number: unique serial number of the sensor in decimal
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=================== ============================================================
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