Magnetometer Calibration Tool

The navXMagCalibrator tool is used to calibrate the VMX-pi magnetometer.

Installing the navXMagCalibrator

  • Download the latest build.
  • Unpack the contents of the file and run the setup.exe program, which will install the navXUI, as well as all necessary device drivers for communicating over USB with the VMX-pi, as well as some additional tools.
  • Connect the USB cable between the VMX-pi circuit board and your Windows computer.

Running the navXMagCalibrator

Start the navXMagCalibrator

From your windows start menu, first select “Kauai Labs” and then “VMX-pi” and click on the navXMagCalibrator item.


Connecting to VMX-pi

Once the navXMagCalibrator application is started, select the COM Port on which your VMX-pi is connected, and press the “Open” button. If VMX-pi is successfully opened, you will see information about the VMX-pi circuit board:


You will need to take 12 separate data points. Starting with the “X+” axis, click on the help button (labeled ‘?’) to the right of the X+ controls. This will bring up an Axis orientation dialog. Carefully align the VMX-pi such that it’s X, Y an Z axes (see silkscreen on the VMX-pi circuit board) are in the orientation shown in the dialog, relative to reference coordinates – for instance the edge of a square table.


Once you have aligned the device for this first reading, press the “Point 0 degrees” button to store the current magnetometer readings corresponding to this orientation.


Repeat this process for all data points, until all 12 sets of data points have been collected.


Next, press the “Calculate Transformation Matrix and Bias” button. You will see the results of this displayed in the “Transform Matrix” and “Bias” controls section on the bottom left of the navXMagCalibrator window.

If the data points you have taken are invalid, you may receive a message indicating there are invalid data points. In this case, restart taking the data points, repeat the process above until you have a valid set of data points.


Once a set of valid data points has been acquired, press the “Save to NavX-Family Device” button to store the calibration data to the VMX-pi circuit board. This calibration data is stored to VMX-pi’s onboard flash memory, so this calibration data will be saved for future use.

Once the data has been saved to VMX-pi, the VMX-pi circuit board will immediately begin using the calibration data. At this point, the “compass heading”, the “9-axis heading” and the “magnetic disturbance detection” features will begin working. These capabilities can be demonstrated via the navXUI.