Drivers:

You might need to download the FTDI drivers if you do not have it on your computer already. Visit the FTDI website to locate these drivers here: http://www.ftdichip.com/Drivers/VCP.htm

View Data Stream with Arduino:

Open Arduino, go to Tools -> Serial Port, and choose the port the GCU is using.

In Windows, this will show up as a COM port. To find which one is the GCU, look at the menu list while the GCU USB unplugged. Plug the USB for the GCU into your computer. Look at this list again, the new COM port is the one the GCU is using.

Select the GCU COM port in Tools->Serial Port. Click on the right-most button in the Arduino window (the tool tip will say "Serial Monitor"). A window will pop up. Choose 115200 baud as the speed in the window. You should now see text streaming into the window.

Data Logging via PuttyTel:

Unfortunately, Arduino can't log this text to a file, we'll need to use a different application. For Windows, download puttytel from here:

http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html

You'll want use a serial connection as described here:

http://tartarus.org/~simon/putty-snapshots/htmldoc/Chapter3.html#using-serial

"Serial Line" will be COM1 or COM2, etc that the GCU is using.
Serial speed will be 115200 baud.

There is another configuration pane for datalogging. You can choose where to save the data file, and PuttyTel can name each log file based on the date/time via the %Y,%M, etc tags. Use a .csv extension as part of the name. Excel and other applications should be able to read that file.

Data Logging with the GCU