If you have ever taken a PC onboard a boat and connected it up to a GPS via a serial or USB port then the chances are that you will probably have seen the occasional “crazy mouse” behaviour that seems to affect so many marine PCs. The cursor will suddenly start to randomly move all over the screen, opening windows and clicking on things, as if possessed by some nautical demon !
Well there is a very simple explanation for this phenomenon and it dates back to the good old Serial Port mouse that was popular on the first Windows PCs. It was the mouse with the large 9 pin D-Type connector on the end of the cable, that came out before the short lived PS2 connector mouse and the more recent USB mouse.
These original Serial Port mice used a series of ASCII control signals that are very similar to those produced by a typical NMEA0183 interface on a modern GPS or chart Plotter. If the GPS or Plotter is turned on when the PC boots up, Windows detects the NMEA0183 signals, thinks it has an old Serial Mouse connected and loads up some very old driver software that then proceeds to move the cursor all over the place, opening and closing windows and generally behaving like a “crazy mouse”.
All of the releases of Windows have suffered from this problem and even the very latest Windows 8.1 still has this old Serial Mouse detection software included and will go crazy in certain conditions. The good news is that it is pretty easy to fix, by going in to Device Manager and disabling (NOT uninstalling) the Serial Port Mouse. Digital Yacht have produced a Tech Note on how to fix the problem and a copy can be downloaded by clicking here.