Virtual Comm Port …pitfalls, and crazy mouse

IMG_0737Well here we are in 2012, and navigation equipment manufacturers still don’t know that laptops don’t have serial ports anymore. If you want NMEA data fed from your instruments into your chart plotting software you are forced to use USB/serial port converters. This means that you will need to create what’s called a virtual comm port and that in turn needs a special software driver. This is when the fun starts.

Whatever you do don’t but any USB / Serial converters that use Prolific software drivers. Don’t do what I did and ask for or shop for “Windows 7 compatible” converters – that is not enough. Prolific are a good company but unfortunately for them it appears that there are a lot of cheap Chinese converters on the market with hacked Prolific IC’s and useless software drivers that simply do not work…

Here is the warning on the Prolific website: “Please be warned that counterfeit (fake) PL-2303HX (Chip Rev A) USB to Serial Controller ICs using Prolific’s trademark logo, brandname, and device drivers, were being sold in the China market. Counterfeit IC products show exactly the same outside chip markings but generally are of poor quality and causes Windows driver compatibility issues (Yellow Mark Error Code 10). We issue this warning to all our customers and consumers to avoid confusion and false purchase.”

Go for converters that use the FTDI chip set and matching software drivers. The one that I have gone for is the FTDI USB to Serial RS232 Adapter Cable with COM Retention. This works perfectly with Windows7 and also as the name implies always comes up with the same comm port number when you re-use it. This helps with configuring chart plotting software to always look at the same comm pot on each use.

There is still something waiting to bite you however. Do you remember “crazy mouse”. That was when the operating system decides that your USB/Serial converter is a mouse – and your cursor and mouse pointer starts careering all over the screen launching program at random. I thought those days were over – until today!

For no apparent reason the perfectly working USB/Serial converters (I have two of them plugged in) were suddenly identified by Windows 7 as a “Microsoft wheel mouse”….and off it went – crazy mouse all over again – I couldn’t believe it! I realise that it is the stream of NMEA or GPS data that gets interpreted by the Windows as mouse data – but really – it is not beyond the wit of man to work this all out…well I guess it is beyond the wit of some programmers at Microsoft.

The solution in my case was to let the crazy mouse happen – unplug the converter (you get mouse/track pad control back then) and immediately go into Device Manager and “Disable” (right click) the erroneous “Microsoft Serial Ball Point” device listed. Generally I tend to boot the laptop with the USB/serial convertor disconnected; wait until all the drivers are loaded and the laptop is just idle (3 mins); then connect the USB/serial convertors. I also recommend creating a shortcut to “device” settings on your desktop – you will be in and out of these a lot checking on the virtual comm port drivers!

If the technique above doesn’t work for you, then I recommend reading this document from Jeppesen; or from CAP’N; or from  Coastal Explorer…and trying the techniques described there.

Good luck!.


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