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linux/Documentation/ABI/testing/sysfs-i2c-bmp085

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drivers/misc: support for the pressure sensor BMP085 from Bosch Sensortec This driver adds support for the BMP085 digital pressure sensor from Bosch Sensortec. It exposes a sysfs api to userspace where pressure and temperature measurement results can be read from the pressure0_input and temp0_input file. The chip is able to calculate the average of up to eight samples to increase the accuracy. This feature can be controlled by writing to the oversampling file. The BMP085 digital pressure sensor can measure ambient air pressure and temperature. Both values can be obtained from sysfs files. The pressure is measured by reading from pressure0_input. Valid values range from 30000 to 110000 pascal with a resolution of 1 pascal (=0.01 millibar). temp0_input holds the current temperature in degree celsius, multiplied by 10. This results in a resolution of a tenth degree celsius. Values range from -400 to 850. To increase the accuracy, this chip can calculate the average of 1, 2, 4 or 8 samples. This behavior is controlled through the oversampling sysfs file. Two to the power of the value written to that file specifies how many samples will be used. Valid values: 0..3. [akpm@linux-foundation.org: fix typo] [shubhrajyoti@ti.com: optimize the wait time for the pressure sensor, definition of long is arch dependent so make it u32] [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Christoph Mair <christoph.mair@gmail.com> Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com> Acked-by: Jonathan Cameron <jic23@cam.ac.uk> Cc: Stefan Schmidt <stefan@datenfreihafen.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-08-10 08:20:28 +08:00
What: /sys/bus/i2c/devices/<busnum>-<devaddr>/pressure0_input
Date: June 2010
Contact: Christoph Mair <christoph.mair@gmail.com>
Description: Start a pressure measurement and read the result. Values
represent the ambient air pressure in pascal (0.01 millibar).
Reading: returns the current air pressure.
What: /sys/bus/i2c/devices/<busnum>-<devaddr>/temp0_input
Date: June 2010
Contact: Christoph Mair <christoph.mair@gmail.com>
Description: Measure the ambient temperature. The returned value represents
the ambient temperature in units of 0.1 degree celsius.
Reading: returns the current temperature.
What: /sys/bus/i2c/devices/<busnum>-<devaddr>/oversampling
Date: June 2010
Contact: Christoph Mair <christoph.mair@gmail.com>
Description: Tell the bmp085 to use more samples to calculate a pressure
value. When writing to this file the chip will use 2^x samples
to calculate the next pressure value with x being the value
written. Using this feature will decrease RMS noise and
increase the measurement time.
Reading: returns the current oversampling setting.
Writing: sets a new oversampling setting.
Accepted values: 0..3.