Tablet mouse cursor moves erratically across screen

18 Apr 2025

Description of Problem:
This condition is potentially encountered in Microsoft Windows when connecting a serial GPS device to a serial port. It is caused when the NMEA GPS serial data is misinterpreted as mouse data by the serial port enumerator, resulting in erratic mouse cursor activity. These instructions were tested in Windows 11 and can be adapted for Windows 10 (or earlier) operating systems.

Potential Fix:

  1. Disable the Serial GPS Device
    • To gain control of the mouse, first make sure that the attached NMEA data source (e.g., GPS) is powered off. The 9 pin serial cable needs to be physically connected to the dock or tablet. If it isn't, the port will not show in device manager. The GPS unit should be powered off but still connected. 
  2. Locate the USB / Serial COM Port in Windows Device Manager
    • Access the Power Users Menu by right-clicking the Windows icon (or Start button) in the lower left corner of the screen. Alternately, press the keyboard shortcut: [Windows key] + X.
    • Select Device Manager from the menu.

A screenshot of a computer program AI-generated content may be incorrect.

    • In the Device Manager window, expand the ‘Ports (COM & LPT)’ section by clicking on the ‘>’ or triangle, as shown.

 

  1. Disable the Serial Port Enumerator
    • Under ‘Ports (COM & LPT)’, double-click on the USB serial device entry to bring up the Device Properties dialog box
    • In the Device Properties window, click the ‘Port Settings’ tab
    • Click the ‘Advanced’ button, as shown, to open the Advanced Settings window.

A screenshot of a computer AI-generated content may be incorrect.

    • In the Advanced Settings window, locate the "Miscellaneous Options" section and uncheck the box for ‘Serial Enumerator’, as shown. 

    • Click the OK button to confirm your changes and close the Device Properties window.
    • Close the Device Manager by clicking the ‘X’ in the top-right corner.
    • A Windows restart is required to apply the settings after the serial enumerator is unchecked.

If further assistance is needed, contact the HarvestMaster Field Service Engineers. For contact information, see Contact a HarvestMaster Field Service Engineer.