From 42b743c85597e982ff1122b972862396f131db34 Mon Sep 17 00:00:00 2001 From: Mathias Agopian Date: Mon, 22 Nov 2010 15:55:32 -0800 Subject: update rotation-vector documentation. the rotation-vector sensor must transmit the W component of the unit quaternion in data[4]. This change doesn't cause a compatibility issue because nothing in the system relies on the W component being present. Change-Id: If4f699ac8d41d8b957925b375e355a138a82dcf8 --- include/hardware/sensors.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'include/hardware') 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 . * 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 { -- cgit v1.1