| David Frey | 7c84f7f | 2016-06-02 09:59:11 +0200 | [diff] [blame] | 1 | Kernel driver sht3x |
| 2 | =================== |
| 3 | |
| 4 | Supported chips: |
| 5 | * Sensirion SHT3x-DIS |
| 6 | Prefix: 'sht3x' |
| 7 | Addresses scanned: none |
| 8 | Datasheet: http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/Humidity/Sensirion_Humidity_Datasheet_SHT3x_DIS.pdf |
| 9 | |
| 10 | Author: |
| 11 | David Frey <david.frey@sensirion.com> |
| 12 | Pascal Sachs <pascal.sachs@sensirion.com> |
| 13 | |
| 14 | Description |
| 15 | ----------- |
| 16 | |
| 17 | This driver implements support for the Sensirion SHT3x-DIS chip, a humidity |
| 18 | and temperature sensor. Temperature is measured in degrees celsius, relative |
| 19 | humidity is expressed as a percentage. In the sysfs interface, all values are |
| 20 | scaled by 1000, i.e. the value for 31.5 degrees celsius is 31500. |
| 21 | |
| 22 | The device communicates with the I2C protocol. Sensors can have the I2C |
| 23 | addresses 0x44 or 0x45, depending on the wiring. See |
| 24 | Documentation/i2c/instantiating-devices for methods to instantiate the device. |
| 25 | |
| 26 | There are two options configurable by means of sht3x_platform_data: |
| 27 | 1. blocking (pull the I2C clock line down while performing the measurement) or |
| 28 | non-blocking mode. Blocking mode will guarantee the fastest result but |
| 29 | the I2C bus will be busy during that time. By default, non-blocking mode |
| 30 | is used. Make sure clock-stretching works properly on your device if you |
| 31 | want to use blocking mode. |
| 32 | 2. high or low accuracy. High accuracy is used by default and using it is |
| 33 | strongly recommended. |
| 34 | |
| 35 | The sht3x sensor supports a single shot mode as well as 5 periodic measure |
| 36 | modes, which can be controlled with the update_interval sysfs interface. |
| 37 | The allowed update_interval in milliseconds are as follows: |
| 38 | * 0 single shot mode |
| 39 | * 2000 0.5 Hz periodic measurement |
| 40 | * 1000 1 Hz periodic measurement |
| 41 | * 500 2 Hz periodic measurement |
| 42 | * 250 4 Hz periodic measurement |
| 43 | * 100 10 Hz periodic measurement |
| 44 | |
| 45 | In the periodic measure mode, the sensor automatically triggers a measurement |
| 46 | with the configured update interval on the chip. When a temperature or humidity |
| 47 | reading exceeds the configured limits, the alert attribute is set to 1 and |
| 48 | the alert pin on the sensor is set to high. |
| 49 | When the temperature and humidity readings move back between the hysteresis |
| 50 | values, the alert bit is set to 0 and the alert pin on the sensor is set to |
| 51 | low. |
| 52 | |
| 53 | sysfs-Interface |
| 54 | --------------- |
| 55 | |
| 56 | temp1_input: temperature input |
| 57 | humidity1_input: humidity input |
| 58 | temp1_max: temperature max value |
| 59 | temp1_max_hyst: temperature hysteresis value for max limit |
| 60 | humidity1_max: humidity max value |
| 61 | humidity1_max_hyst: humidity hysteresis value for max limit |
| 62 | temp1_min: temperature min value |
| 63 | temp1_min_hyst: temperature hysteresis value for min limit |
| 64 | humidity1_min: humidity min value |
| 65 | humidity1_min_hyst: humidity hysteresis value for min limit |
| 66 | temp1_alarm: alarm flag is set to 1 if the temperature is outside the |
| 67 | configured limits. Alarm only works in periodic measure mode |
| 68 | humidity1_alarm: alarm flag is set to 1 if the humidity is outside the |
| 69 | configured limits. Alarm only works in periodic measure mode |
| Matt Ranostay | 50c22cd | 2016-07-09 23:49:18 -0700 | [diff] [blame] | 70 | heater_enable: heater enable, heating element removes excess humidity from |
| 71 | sensor |
| 72 | 0: turned off |
| 73 | 1: turned on |
| David Frey | 7c84f7f | 2016-06-02 09:59:11 +0200 | [diff] [blame] | 74 | update_interval: update interval, 0 for single shot, interval in msec |
| 75 | for periodic measurement. If the interval is not supported |
| 76 | by the sensor, the next faster interval is chosen |