72 lines
2.7 KiB
Plaintext
72 lines
2.7 KiB
Plaintext
Kernel driver lis3lv02d
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=======================
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Supported chips:
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* STMicroelectronics LIS3LV02DL and LIS3LV02DQ
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Authors:
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Yan Burman <burman.yan@gmail.com>
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Eric Piel <eric.piel@tremplin-utc.net>
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Description
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-----------
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This driver provides support for the accelerometer found in various HP
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laptops sporting the feature officially called "HP Mobile Data
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Protection System 3D" or "HP 3D DriveGuard". It detects automatically
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laptops with this sensor. Known models (for now the HP 2133, nc6420,
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nc2510, nc8510, nc84x0, nw9440 and nx9420) will have their axis
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automatically oriented on standard way (eg: you can directly play
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neverball). The accelerometer data is readable via
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/sys/devices/platform/lis3lv02d.
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Sysfs attributes under /sys/devices/platform/lis3lv02d/:
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position - 3D position that the accelerometer reports. Format: "(x,y,z)"
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calibrate - read: values (x, y, z) that are used as the base for input
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class device operation.
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write: forces the base to be recalibrated with the current
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position.
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rate - reports the sampling rate of the accelerometer device in HZ
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This driver also provides an absolute input class device, allowing
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the laptop to act as a pinball machine-esque joystick.
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Another feature of the driver is misc device called "freefall" that
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acts similar to /dev/rtc and reacts on free-fall interrupts received
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from the device. It supports blocking operations, poll/select and
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fasync operation modes. You must read 1 bytes from the device. The
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result is number of free-fall interrupts since the last successful
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read (or 255 if number of interrupts would not fit).
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Axes orientation
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----------------
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For better compatibility between the various laptops. The values reported by
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the accelerometer are converted into a "standard" organisation of the axes
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(aka "can play neverball out of the box"):
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* When the laptop is horizontal the position reported is about 0 for X and Y
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and a positive value for Z
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* If the left side is elevated, X increases (becomes positive)
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* If the front side (where the touchpad is) is elevated, Y decreases
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(becomes negative)
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* If the laptop is put upside-down, Z becomes negative
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If your laptop model is not recognized (cf "dmesg"), you can send an
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email to the authors to add it to the database. When reporting a new
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laptop, please include the output of "dmidecode" plus the value of
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/sys/devices/platform/lis3lv02d/position in these four cases.
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Q&A
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---
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Q: How do I safely simulate freefall? I have an HP "portable
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workstation" which has about 3.5kg and a plastic case, so letting it
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fall to the ground is out of question...
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A: The sensor is pretty sensitive, so your hands can do it. Lift it
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into free space, follow the fall with your hands for like 10
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centimeters. That should be enough to trigger the detection.
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