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| -rw-r--r-- | Documentation/hwmon/sht21 | 50 |
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diff --git a/Documentation/hwmon/sht21 b/Documentation/hwmon/sht21 new file mode 100644 index 000000000..8b3cdda54 --- /dev/null +++ b/Documentation/hwmon/sht21 @@ -0,0 +1,50 @@ +Kernel driver sht21 +=================== + +Supported chips: + * Sensirion SHT21 + Prefix: 'sht21' + Addresses scanned: none + Datasheet: Publicly available at the Sensirion website + http://www.sensirion.com/file/datasheet_sht21 + + * Sensirion SHT25 + Prefix: 'sht25' + Addresses scanned: none + Datasheet: Publicly available at the Sensirion website + http://www.sensirion.com/file/datasheet_sht25 + +Author: + Urs Fleisch <urs.fleisch@sensirion.com> + +Description +----------- + +The SHT21 and SHT25 are humidity and temperature sensors in a DFN package of +only 3 x 3 mm footprint and 1.1 mm height. The difference between the two +devices is the higher level of precision of the SHT25 (1.8% relative humidity, +0.2 degree Celsius) compared with the SHT21 (2.0% relative humidity, +0.3 degree Celsius). + +The devices communicate with the I2C protocol. All sensors are set to the same +I2C address 0x40, so an entry with I2C_BOARD_INFO("sht21", 0x40) can be used +in the board setup code. + +sysfs-Interface +--------------- + +temp1_input - temperature input +humidity1_input - humidity input +eic - Electronic Identification Code + +Notes +----- + +The driver uses the default resolution settings of 12 bit for humidity and 14 +bit for temperature, which results in typical measurement times of 22 ms for +humidity and 66 ms for temperature. To keep self heating below 0.1 degree +Celsius, the device should not be active for more than 10% of the time, +e.g. maximum two measurements per second at the given resolution. + +Different resolutions, the on-chip heater, and using the CRC checksum +are not supported yet. |