bindings/iio/mount-matrix.txt

2 * is the definition of +/- values practical or counterintuitive?
13 that produce three-dimensional data in relation to the world where it is
22 and thus implying that the component should be mounted in a certain orientation
27 mounted on the same chassis as this screen, will likely take the screen as
36 A sensor can be mounted in any angle along the axes relative to the frame of
37 reference. This means that the sensor may be flipped upside-down, left-right,
47 Device-to-world examples for some three-dimensional sensor types:
49 - Accelerometers have their world frame of reference toward the center of
57   as the gravity vector is projected 1:1 onto the sensors (z)-axis.
60   is projected onto the (x,y) plane of the display panel.
67      +--------+             +--------+
69      +--------+             +--------+
80      (---------)
81      !         !           y: -g
85      !         !  x: +g <- z: +g  -> x: -g
90      (---------)
93 - Magnetometers (compasses) have their world frame of reference relative to the
94   geomagnetic field. The system orientation vis-a-vis the world is defined with
103      (---------)
113      (---------)
129 - Gyroscopes detects the movement relative the device itself. The angular
134   counter-clockwise according to the right-hand rule.
137      (---------)     y > 0
138      !         !     v---\
141      !         !      <--\
143      ! 1  2  3 !       --/
147      (---------)
150 So unless the sensor is ideally mounted, we need a means to indicate the
154 To achieve this, use the device tree property "mount-matrix" for the sensor.
159 multiplied by this matrix to give the proper vectors values in three-dimensional
183 mechanically mounted in an ideal way and we need no transformation):
185 mount-matrix = "1", "0", "0",
189 The sensor is mounted 30 degrees (Pi/6 radians) tilted along the X axis, so we
190 compensate by performing a -30 degrees rotation around the X axis:
192 mount-matrix = "1", "0", "0",
194                "0", "-0.5", "0.866";
196 The sensor is flipped 180 degrees (Pi radians) around the Z axis, i.e. mounted
197 upside-down:
199 mount-matrix = "0.998", "0.054", "0",
200                "-0.054", "0.998", "0",
203 ???: this does not match "180 degrees" - factors indicate ca. 3 degrees compensation