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Diffstat (limited to 'Documentation/ABI/testing/sysfs-bus-iio')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-iio | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio index a9d51810a3ba..e3df71987eff 100644 --- a/Documentation/ABI/testing/sysfs-bus-iio +++ b/Documentation/ABI/testing/sysfs-bus-iio @@ -65,6 +65,7 @@ Contact: linux-iio@vger.kernel.org Description: When the internal sampling clock can only take a specific set of frequencies, we can specify the available values with: + - a small discrete set of values like "0 2 4 6 8" - a range with minimum, step and maximum frequencies like "[min step max]" @@ -1627,17 +1628,21 @@ Description: Mounting matrix for IIO sensors. This is a rotation matrix which informs userspace about sensor chip's placement relative to the main hardware it is mounted on. + Main hardware placement is defined according to the local reference frame related to the physical quantity the sensor measures. + Given that the rotation matrix is defined in a board specific way (platform data and / or device-tree), the main hardware reference frame definition is left to the implementor's choice (see below for a magnetometer example). + Applications should apply this rotation matrix to samples so that when main hardware reference frame is aligned onto local reference frame, then sensor chip reference frame is also perfectly aligned with it. + Matrix is a 3x3 unitary matrix and typically looks like [0, 1, 0; 1, 0, 0; 0, 0, -1]. Identity matrix [1, 0, 0; 0, 1, 0; 0, 0, 1] means sensor chip and main hardware @@ -1646,8 +1651,10 @@ Description: For example, a mounting matrix for a magnetometer sensor informs userspace about sensor chip's ORIENTATION relative to the main hardware. + More specifically, main hardware orientation is defined with respect to the LOCAL EARTH GEOMAGNETIC REFERENCE FRAME where : + * Y is in the ground plane and positive towards magnetic North ; * X is in the ground plane, perpendicular to the North axis and positive towards the East ; @@ -1656,13 +1663,16 @@ Description: An implementor might consider that for a hand-held device, a 'natural' orientation would be 'front facing camera at the top'. The main hardware reference frame could then be described as : + * Y is in the plane of the screen and is positive towards the top of the screen ; * X is in the plane of the screen, perpendicular to Y axis, and positive towards the right hand side of the screen ; * Z is perpendicular to the screen plane and positive out of the screen. + Another example for a quadrotor UAV might be : + * Y is in the plane of the propellers and positive towards the front-view camera; * X is in the plane of the propellers, perpendicular to Y axis, @@ -1704,6 +1714,7 @@ Description: This interface is deprecated; please use the Counter subsystem. A list of possible counting directions which are: + - "up" : counter device is increasing. - "down": counter device is decreasing. |