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