on the old versions of OLpcPRO and Roboguide, under the teach pendant there was a tab you could click to set the destination of UD1 and MC to a usb in your computer or anyplace you might want to map it to.
I took me a little time to locate how to do so in the new version so I thought I would just mention it.
If you double click on Robot controller on the main page (see attached) you can set it there.
