I wanted to read track data from any Garmin GPS device directly via my C# code. I found lots of classes and libraries for free and lots of where I had to pay for. But all of them had the same problem that communication via the COM Port seems to be verry buggy. I decided to develop my own and found that this is not that easy ;-(.
You will find the Java Script sources together with some examples and the documentation at the Garmin Website: http://developer.garmin.com/web-device/garmin-communicator-plugin/