This video shows an ODROID U-3 single-board computer running a Python program that talks to a an AcroNaze32 flight controller (FC) over USB. The Python program uses MSPPG, our Multiwii Serial Protocol Parser Generator library, to serialize up/down/up/down MSP_SET_RAW_RC messages to the FC. By polling the incoming R/C receiver channels using an MSP_RC message, we were able to have the Python program switch the autopilot on and off without the need for an additional microcontroller. The ODROID is powered by the clean 5v ESC output on the FC.
You can get the code for this example from https://github.com/simondlevy/MSPPG. Remember to remove all propellers before testing!