The m3pi robot has a socket for a Wixel module. The Wixel can be used with its stock wireless serial app to easily add wireless functionality to your m3pi robot, or you can take it a step further and program it to act as the main controller of your m3pi.
As long as the m3pi expansion board has shorting blocks on its three serial jumpers and the 3pi robot base is running its stock serial slave program (or the most recent version of the 3pi demo program), a socketed Wixel can control the 3pi base through a series of serial commands while simultaneously performing high-level tasks like wireless communication, route planning, and sensor processing.
There is currently no Wixel library specifically for controlling the m3pi, so there is a bit more programming involved in getting started with the Wixel than with the mbed. The serial commands for controlling the 3pi base are documented in the section of the 3pi user’s guide on the serial slave program. The 3pi robot included with the fully-assembled m3pi is pre-programed with this serial slave program.
If you are using the m3pi expansion kit to upgrade your 3pi robot to a Wixel-controlled m3pi robot, you should use your AVR programmer to load the serial slave program onto the 3pi. The source code for the serial slave program is included with the Pololu AVR library, as is a precompiled hex file.