You can't have the Position Controller and DC Motor Controller examples open at the same time (this is why the info box for the position controller window says "Attached: Nothing"). This is because both of those windows use the DCMotor channel of the DCC1001, whereas the encoder window uses the Encoder channel. If you want to run the motor at a certain duty cycle in one direction, use the DC Motor Controller example. If you want position control with a PID control loop, use the Position Controller.
We've just been made aware of this issue. There'll be a fix in the next version of the libraries. In the meantime, you may be able to get it working by downloading the C# PositionController example, which is the same program.
There is another issue when using the DC Motor Controller program.
I've been changing the parameters (target velocity, acceleration, current limit) and the motor does not spin. I measured the voltage on M+ and M- and there is nothing there.
