The test setup is the motor shield + arduino 2009 + potentiometer + dc motor
The potentiometer is being fed with
note: maybe the maximum reference is still 5v ??
a 3.3v is provided to the outputs of the l293 on the motor shield, by an external power source (in the future this will come from and independent 3v3 regulator, powered by a 3v7 LiPo battery).
the program running at arduino implements a PID control with the aid of the Arduino - PIDLibrary.