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| -rw-r--r-- | include/hardware/sensors.h | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/include/hardware/sensors.h b/include/hardware/sensors.h index 90568eb..7f9706b 100644 --- a/include/hardware/sensors.h +++ b/include/hardware/sensors.h @@ -233,12 +233,19 @@ __BEGIN_DECLS * A gravity output indicates the direction of and magnitude of gravity in the devices's * coordinates. On Earth, the magnitude is 9.8. Units are m/s^2. The coordinate system * is the same as is used for the acceleration sensor. + * When the device is at rest, the output of the gravity sensor should be identical + * to that of the accelerometer. * * Linear Acceleration * ------------------- * Indicates the linear acceleration of the device in device coordinates, not including gravity. * This output is essentially Acceleration - Gravity. Units are m/s^2. The coordinate system is * the same as is used for the acceleration sensor. + * The output of the accelerometer, gravity and linear-acceleration sensors must obey the + * following relation: + * + * acceleration = gravity + linear-acceleration + * * * Rotation Vector * --------------- @@ -252,6 +259,14 @@ __BEGIN_DECLS * unit quaternion <cos(theta/2), x*sin(theta/2), y*sin(theta/2), z*sin(theta/2)>. * Elements of the rotation vector are unitless. The x, y, and z axis are defined * in the same was as for the acceleration sensor. + * + * The rotation-vector is stored as: + * + * sensors_event_t.data[0] = x*sin(theta/2) + * sensors_event_t.data[1] = y*sin(theta/2) + * sensors_event_t.data[2] = z*sin(theta/2) + * sensors_event_t.data[3] = cos(theta/2) + * */ typedef struct { |