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Diffstat (limited to 'Documentation/hwmon/sht3x')
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diff --git a/Documentation/hwmon/sht3x b/Documentation/hwmon/sht3x new file mode 100644 index 000000000..b0d88184f --- /dev/null +++ b/Documentation/hwmon/sht3x @@ -0,0 +1,76 @@ +Kernel driver sht3x +=================== + +Supported chips: + * Sensirion SHT3x-DIS + Prefix: 'sht3x' + Addresses scanned: none + Datasheet: http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_Datasheet_SHT3x_DIS.pdf + +Author: + David Frey <david.frey@sensirion.com> + Pascal Sachs <pascal.sachs@sensirion.com> + +Description +----------- + +This driver implements support for the Sensirion SHT3x-DIS chip, a humidity +and temperature sensor. Temperature is measured in degrees celsius, relative +humidity is expressed as a percentage. In the sysfs interface, all values are +scaled by 1000, i.e. the value for 31.5 degrees celsius is 31500. + +The device communicates with the I2C protocol. Sensors can have the I2C +addresses 0x44 or 0x45, depending on the wiring. See +Documentation/i2c/instantiating-devices for methods to instantiate the device. + +There are two options configurable by means of sht3x_platform_data: +1. blocking (pull the I2C clock line down while performing the measurement) or + non-blocking mode. Blocking mode will guarantee the fastest result but + the I2C bus will be busy during that time. By default, non-blocking mode + is used. Make sure clock-stretching works properly on your device if you + want to use blocking mode. +2. high or low accuracy. High accuracy is used by default and using it is + strongly recommended. + +The sht3x sensor supports a single shot mode as well as 5 periodic measure +modes, which can be controlled with the update_interval sysfs interface. +The allowed update_interval in milliseconds are as follows: + * 0 single shot mode + * 2000 0.5 Hz periodic measurement + * 1000 1 Hz periodic measurement + * 500 2 Hz periodic measurement + * 250 4 Hz periodic measurement + * 100 10 Hz periodic measurement + +In the periodic measure mode, the sensor automatically triggers a measurement +with the configured update interval on the chip. When a temperature or humidity +reading exceeds the configured limits, the alert attribute is set to 1 and +the alert pin on the sensor is set to high. +When the temperature and humidity readings move back between the hysteresis +values, the alert bit is set to 0 and the alert pin on the sensor is set to +low. + +sysfs-Interface +--------------- + +temp1_input: temperature input +humidity1_input: humidity input +temp1_max: temperature max value +temp1_max_hyst: temperature hysteresis value for max limit +humidity1_max: humidity max value +humidity1_max_hyst: humidity hysteresis value for max limit +temp1_min: temperature min value +temp1_min_hyst: temperature hysteresis value for min limit +humidity1_min: humidity min value +humidity1_min_hyst: humidity hysteresis value for min limit +temp1_alarm: alarm flag is set to 1 if the temperature is outside the + configured limits. Alarm only works in periodic measure mode +humidity1_alarm: alarm flag is set to 1 if the humidity is outside the + configured limits. Alarm only works in periodic measure mode +heater_enable: heater enable, heating element removes excess humidity from + sensor + 0: turned off + 1: turned on +update_interval: update interval, 0 for single shot, interval in msec + for periodic measurement. If the interval is not supported + by the sensor, the next faster interval is chosen |