diff options
| author | Urs Fleisch <urs.fleisch@gmail.com> | 2011-01-07 07:15:39 +0000 |
|---|---|---|
| committer | Guenter Roeck <guenter.roeck@ericsson.com> | 2011-01-08 10:56:28 -0800 |
| commit | 430400b86304ea729ba10f2966a8af67da60a37f (patch) | |
| tree | 79abaa76d689a40923167103582bb11e69fd096c /Documentation/hwmon | |
| parent | c6c2c1636e30bcd26c6b0d208324055a03c5ab9c (diff) | |
hwmon: driver for Sensirion SHT21 humidity and temperature sensor
Signed-off-by: Urs Fleisch <urs.fleisch@sensirion.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
Diffstat (limited to 'Documentation/hwmon')
| -rw-r--r-- | Documentation/hwmon/sht21 | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/Documentation/hwmon/sht21 b/Documentation/hwmon/sht21 new file mode 100644 index 000000000000..db17fda45c3e --- /dev/null +++ b/Documentation/hwmon/sht21 @@ -0,0 +1,49 @@ +Kernel driver sht21 +=================== + +Supported chips: + * Sensirion SHT21 + Prefix: 'sht21' + Addresses scanned: none + Datasheet: Publicly available at the Sensirion website + http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT21.pdf + + * Sensirion SHT25 + Prefix: 'sht21' + Addresses scanned: none + Datasheet: Publicly available at the Sensirion website + http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT25.pdf + +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 + +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, using the CRC checksum and reading +the serial number are not supported yet. |