| William Markezana | f060c65 | 2013-08-29 13:51:42 +0200 | [diff] [blame] | 1 | Kernel driver htu21 |
| 2 | =================== |
| 3 | |
| 4 | Supported chips: |
| 5 | * Measurement Specialties HTU21D |
| 6 | Prefix: 'htu21' |
| 7 | Addresses scanned: none |
| 8 | Datasheet: Publicly available at the Measurement Specialties website |
| 9 | http://www.meas-spec.com/downloads/HTU21D.pdf |
| 10 | |
| 11 | |
| 12 | Author: |
| 13 | William Markezana <william.markezana@meas-spec.com> |
| 14 | |
| 15 | Description |
| 16 | ----------- |
| 17 | |
| 18 | The HTU21D is a humidity and temperature sensor in a DFN package of |
| 19 | only 3 x 3 mm footprint and 0.9 mm height. |
| 20 | |
| 21 | The devices communicate with the I2C protocol. All sensors are set to the |
| 22 | same I2C address 0x40, so an entry with I2C_BOARD_INFO("htu21", 0x40) can |
| 23 | be used in the board setup code. |
| 24 | |
| 25 | This driver does not auto-detect devices. You will have to instantiate the |
| 26 | devices explicitly. Please see Documentation/i2c/instantiating-devices |
| 27 | for details. |
| 28 | |
| 29 | sysfs-Interface |
| 30 | --------------- |
| 31 | |
| 32 | temp1_input - temperature input |
| 33 | humidity1_input - humidity input |
| 34 | |
| 35 | Notes |
| 36 | ----- |
| 37 | |
| 38 | The driver uses the default resolution settings of 12 bit for humidity and 14 |
| 39 | bit for temperature, which results in typical measurement times of 11 ms for |
| 40 | humidity and 44 ms for temperature. To keep self heating below 0.1 degree |
| 41 | Celsius, the device should not be active for more than 10% of the time. For |
| 42 | this reason, the driver performs no more than two measurements per second and |
| 43 | reports cached information if polled more frequently. |
| 44 | |
| 45 | Different resolutions, the on-chip heater, using the CRC checksum and reading |
| 46 | the serial number are not supported yet. |