OmniMount

If the navX-Micro default yaw axis orientation isn’t sufficient for your needs, you can use the OmniMount feature to re-configure the navX-Micro yaw axis, allowing high-accuracy yaw axis readings when navX-Micro is mounted horizontally, vertically, or even upside down.

In certain cases, the navX-Micro axes (Board Frame) may not be oriented exactly as that of the Robot (Body Frame).   For instance, if the navX-Micro circuit board is mounted sideways, the navX-Micro axes will not be oriented identically to the Robot.  This configuration is shown in the diagram below:

RobotVersesNavXMXPOrientation

Transforming navX-Micro Board Frame to Body Frame with OmniMount

The navX-Micro’s “OmniMount” feature can transform the navX-Micro X, Y and Z axis sensor data (Board Frame) into Robot Orientation (Body Frame) by detecting which of its three axes is perpendicular to the earth’s surface.

This is similar to how a modern smart phone will rotate the display based upon the phone’s orientation.  However unlike a smart phone, the OmniMount detection of orientation does not happen all the time – since the orientation should not change while the robot is moving.  Rather, each time OmniMount configuration occurs, the navX-Micro records this transformation in persistent flash memory, and will continue to perform this transformation until the transform is reconfigured.

To configure OmniMount, follow these simple steps:

  • Install navX-Micro onto your robot. ENSURE that one of the navX-Micro axes (as shown on the navX-Micro circuit board) is perpendicular to the earth’s surface.  This axis will become the yaw (Z) axis.  Note that this axis can either be pointing away from the earth’s surface, or  towards the earth’s surface.
  • Press the ‘CAL’ button on the navX-Micro Circuit board AND HOLD THE BUTTON DOWN FOR AT LEAST 5 SECONDS.
  • Release the ‘CAL’ button, and verify that the orange ‘CAL’ light flashes for 1 second and then turns off.
  • Press the ‘RESET’ button on the navX-Micro circuit board, causing it to restart.
  • The navX-Micro circuit board will now begin OmniMount auto-calibration. During this auto-calibration period, the orange ‘CAL’ LED will flash repeatedly.  This process takes approximately 15 seconds, and requires two things:
    • 1.  During auto-calibration, one of the navX-Micro axes MUST be perpendicular to the earth’s surface.
    • 2.  During auto-calibration, the navX-Micro must be held still.
    • If either of the above conditions is not true, the ‘CAL’ LED will be flashing quickly, indicating an error.  To resolve this error, you must ensure that conditions 1 and 2 are met, at which point the ‘CAL’ LED will begin flashing slowly, indicating calibration is underway.
  • Once the navX-Micro auto-calibration is complete, the Board Frame to Body Frame Transform will be stored persistently into navX-Micro flash memory and used until auto-calibration is run once again.