The navXUI user interface application provides a simple way to visualize the data provided by VMX-pi.


Gyro Calibration in Progress Indicator

The Gyro Calibration in Progress Indicator is displayed during initial gyroscope calibration, which occurs immediately after power is applied to VMX-pi. If the gyroscope calibration does not complete, VMX-pi yaw accuracy will be adversely impacted. For more information on Gyro Calibration, please see the Gyro/Accelerometer Calibration page.

Motion Indicators

VMX-pi provides dynamic motion indicators: (a) the “Moving” indicator and (b) the “Rotating” indicator.

The Moving indicator is present whenever the current Gravity-corrected Linear Acceleration exceeds the “Motion Threshold”.

The Rotating indicator is present whenever the change in yaw value within the last second exceeds the “Rotating Threshold”. Note that VMX-pi Gyroscope Calibration only occurs when VMX-pi is not Rotating for a few seconds.

Gravity-corrected Linear Acceleration (G)

VMX-pi automatically subtracts acceleration due to gravity from accelerometer data, and displays the resulting linear acceleration. These measures are in units of instantaneous G, and are in World Reference Frame.

Sensor Temperature

The Sensor Temperature indicates the die temperature of the MPU-9250 IC. Since shifts in gyro temperature can impact yaw accuracy, VMX-pi will automatically perform Gyroscope calibration whenever VMX-pi is still. See the Gyro/Accelerometer Calibration page for more details.

Magnetic Disturbance Indicator

Once the VMX-pi Magnetometer has been calibrated (see the Magnetometer Calibration page), whenever the current magnetic field diverges from the calibrated value for the earth’s magnetic field, a magnetic disturbance is indicated.

Yaw Angle

The Yaw Angle is displayed in grey text if Gyro Calibration has not yet been completed. Once Gyro Calibration is complete, the Yaw Angle text color will change to white.

Pitch/Roll Angles

The Pitch/Roll Angles are always displayed in white text, since Accelerometer calibration occurs at the Kauai Labs factory.

Compass Angle

The Compass Angle displays the tilt-compensated compass heading calculated from VMX-pi’s Magnetometer combined with the tip/tilt measure from the Accelerometers.

The Compass Angle is displayed in grey text if Magnetometer Calibration has not yet been completed. Once Magnetometer Calibration is complete, the Compass Angle text color will change to white.

9-axis (“Fused”) Heading

The 9-axis heading is displayed in grey text if Magnetometer Calibration has not yet been completed and/or if no undisturbed magnetic readings have occurred.


The Altitude displays the VMX-pi-calculated current altitude, based upon the reading from the pressure sensor, the current temperature and the sea-level pressure.

The Altitude is displayed in red text if a Pressure Sensor is not installed. Pressure Sensors are only installed on VMX-pi Aero. Valid altitude readings are displayed in white text.

Running navXUI

  • Start navXUI:

From your Start Menu, select “Kauai Labs” and then “VMX-pi” and click on the “navXUI” icon to start navXUI.

If your computer has more than one serial port, you can select which serial port to use by clicking on the up/down arrows in the COM port selection control in the UI.