Selecting An Interface - Kauai Labs navX-MXP User Manual

Guidance
Terminology
World Reference Frame solves this issue by providing a reference upon which to measure
"leftness".
To account for this, navX-MXP's motion processing adjusts each linear acceleration value by
rotating it in the opposition direction of the current yaw angle. The result is an acceleration value
that represents acceleration with respect to the area in which navX-MXP operates, which is
known as "World Reference Frame". This world-frame linear acceleration value is much simpler
to use for tracking motion of an object, like a robot, which might rotate while it moves.
Important Note: navX-MXP Linear Acceleration values are in World Reference Frame.
Advanced
Advanced users may require knowledge of the following terminology.
Quaternions
A quaternion is a four-element vector that can be used to encode any rotation in a 3D
coordinate system. This single 4-element vector value can describe not only rotation about a
reference frame's origin (Pitch, Roll and Yaw) but also the rotation of that entire reference
frame with respect to another. Furthermore, when Pitch, Roll and Yaw measures to perform
certain calculations, it is not possible to clearly ascertain orientation when two axes are aligned
with each other; this condition is referred to as "Gimbal Lock". For robotics applications, Pitch,
Roll and Yaw are sufficient, however for certain aerospace applications, Quaternions may be
required to handle all possible orientations.
navX-MXP uses Quaternions internally, and also provides the 4 quaternion values for use by
those who might need them.
The navX-MXP provides several methods for communicating with robotics control applications:
MXP I2C
MXP SPI
USB 2.0
Streaming vs. Register-based Communication
The navX-MXP interfaces fall into two types: Streaming and Register-based.
Streaming: data is sent at regular intervals by the navX-MXP, and the host is notified when new
data arrives. To support the low bitrate of the TTL UART interface, the streaming data is sent in

Selecting an Interface

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